FOUS11 KWBC 182052
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
352 PM EST Thu Dec 18 2025

Valid 00Z Fri Dec 19 2025 - 00Z Mon Dec 22 2025


...Blizzard conditions continue in the Northern Plains through this
evening. See Key Messages linked at the bottom of the discussion=20
for more information...

...Northern Plains, Upper Midwest, Great Lakes...=20
Days 1-2...

At the beginning of the forecast period (00z Fri.) a strong 984 mb
cyclone is forecast to jog northeastward across Lake Superior into
Ontario. While snowfall is rapidly subsiding across the Northern=20
Plains, blizzard conditions will persist into early this evening=20
across portions of the eastern Dakotas and western Minnesota owing
to the gradient winds and fresh snowpack. 1-2" of blowing snow is
also expected over portions of the Minnesota Arrowhead and Upper=20
Peninsula of Michigan, which will support periods of hazardous=20
travel through early tomorrow.=20

As this system continues eastward tonight into Friday, gusty winds
and developing lake effect snow are the most likely winter-related=20
hazards. 850 mb temperatures as low as -15C to -20C are expected
behind the strong cold front as lake temperatures remain largely
around 5C. This temperature delta and brief surge of west-
northwesterly flow will allow for heavy lake effect snow in the
typical snowbelts downwind of Lake Superior and Michigan, with
additional heavy snow possible downwind of Lake Erie and Lake
Ontario. The highest WPC probabilities for at least 6" of snow
through Saturday morning is across the Tug Hill Plateau downwind of
Lake Ontario, where chances sit at 40-70%.=20

...Cascades, Northern Rockies, & Northern California...=20
Days 1-3...

An anchored -WPO/-PNA teleconnection pattern is the culprit in the=20
endless barrage of atmospheric rivers generating copious amounts=20
of snow throughout the mountains of the Pacific Northwest and the=20
Northern Rockies. A persistent feed of Pacific moisture continues=20
to stream as far east as the northern Rockies today. Snow levels=20
in the core of this AR will rise to over 9000ft in Oregon and=20
6000-7000ft in eastern WA. By this evening, a potent cold front=20
advancing south over western WA tonight leads to snow levels
crashing below 2000ft. Farther east, snow levels will rise to=20
6000t in the Bitterroots by tonight and approach 7000ft in the=20
Sawtooth. Before the snow levels rise, however, strong 700mb FGEN=20
is supporting several hours of heavy snow at elevations as low as=20
6000ft in central ID and 5000ft in the Blue Mountains through this=20
evening. Farther south, the Tetons, Absaroka, and Wind River Ranges
will reside closer to stronger 700mb jet and anomalous PWATs (>99th
ECMWF climatological percentiles through Friday afternoon), giving
these ranges both an abundance of moisture and strong upslope=20
enhancement to keep heavy snow in the forecast through Saturday=20
morning for elevation at and above 7000ft.=20

Prolonged Pacific moisture flux will drift southward on Friday with precipitation spreading across northern CA and continue through
Sunday. Snow levels dip to as low as 5,000ft in the Siskiyou and
Shasta, but they only fall in the 8,000-9,000ft elevations on
Saturday before increasing above 9,000ft on Sunday. The lone=20
exception to the higher snow levels and SLRs will be ongoing=20
westerly upslope flow into the WA Cascades where snow levels as low
as around 1,500ft on Saturday and 2,500 ft on Sunday. The bulk of=20
the heaviest snowfall in the WA Cascades and Olympics is expected=20
above 2500ft. WPC 72-hour probabilities show high chances=20
probabilities (>70%) for snowfall totals >18" between 3,000-
4000ft, while similar high chance probabilities exist above 4,000ft
for snowfall totals >30". In the Rockies, high chance=20
probabilities (>70%) for >12" of snow through Friday are present=20
above 5,000ft in the Blue Mountains, Bitterroots, and the Lewis=20
Range, while those same probabilities for >18" are present above=20
6,000ft in the Sawtooth. Snowfall in the Tetons and Wind River=20
Ranges are likely to range between 1-3 feet with some localized=20
amounts approaching 4 feet in the more remote reaches of these=20
ranges through Sunday. The WSSI is keying in on Extreme Impact
potential (extremely dangerous travel, damages to infrastructure=20
in the Wind River, Teton, and Absaroka ranges through Friday night,
largely in the higher reaches of these ranges. Still, Major=20
Impacts (significant travel disruptions) at intermediate=20
elevations of these ranges are likely with heavy snow and whiteout
conditions contributing to the impacts in these ranges to close=20
out the week.=20


The probability of significant icing is less than 10 percent.=20


Mullinax/AA/Snell




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!5l8mDKSbTrGBB2HZ5yAGCRsE22fZKp_zFc6mg68TKkrT-= yNKKjx6qWc5iTxkj-ZSZYprAhzHoh0jGvl5g8UgyrjDGZo$=20



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FOUS11 KWBC 190739
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
239 AM EST Fri Dec 19 2025

Valid 12Z Fri Dec 19 2025 - 12Z Mon Dec 22 2025


...Great Lakes & Northern New England...
Days 1-2...

Negatively tilted upper trough and associated strong cold front is
expected to swing across the Great Lakes and East Coast today
producing a rapid drop in temperatures and gusty winds. This setup
will also provide the opportunity for heavy lake effect and upslope
snow. 850 mb temperatures as low as -15C to -20C are expected
behind the strong cold front as lake temperatures remain largely
around 5C. This temperature delta and brief surge of west-
northwesterly flow will allow for heavy lake effect snow in the
typical snowbelts downwind of Lake Superior and Michigan, with
additional heavier snow possible downwind of Lake Erie and Lake
Ontario given the greater westerly component to the low-level
winds. The highest WPC probabilities for at least 6" of snow
through Saturday morning is across the Tug Hill Plateau downwind of
Lake Ontario, where chances sit at 70-90%. Additionally, some
light to moderate upslope post-frontal snowfall is possible along
the central Appalachians and northern New England elevated west-
northwest facing terrain. Here, WPC probabilities for at least 4
inches of snowfall through 18z Saturday range between 30-60%.


...Cascades, Northern Rockies, & Northern California...
Days 1-3...

An anchored -WPO/-PNA teleconnection pattern is the culprit in the
endless barrage of atmospheric rivers and moist Pacific flow into
the western U.S. This will feed copious amounts of snow throughout
the mountains of the Pacific Northwest and stream as far east as the
Northern Rockies. The strongest IVT signal shifts southward over
the next few days and focuses over southern Oregon and especially
northern California this weekend. It is within this moisture plume
where the highest snow levels above 8000-9000ft reside, with much
lower snow levels to the north across the Pacific Northwest on Day
1 around 1000-2000ft. These lower snow levels also overspread the
northern Rockies by the end of Day 1 after starting in the
5000-6000ft range within the core of the ongoing Atmospheric River.
For the Tetons, Absaroka, and Wind River Ranges, this region will
reside closer to stronger 700mb jet and anomalous PWATs (>99th
ECMWF climatological percentiles through Friday afternoon), giving
these ranges both an abundance of moisture and strong upslope
enhancement to keep heavy snow in the forecast through Saturday
morning for elevation at and above 7000ft. For northern CA, snow
levels dip below 5,000ft in the Siskiyou and Shasta, but as
precipitation also wanes. These levels rise once again above
6000-7000ft with the next AR on Sunday.

The lone exception to the higher snow levels will be ongoing
westerly upslope flow into the WA Cascades as low pressure lingers
off the coast of British Columbia. Snow levels are also expected to
remain quite low and around 1,500ft on Saturday and 2,500 ft on
Sunday. The bulk of the heaviest snowfall in the WA Cascades and
Olympics is expected above 2500ft. WPC 72-hour probabilities show
high chances probabilities (>70%) for snowfall totals >18" between
3,000- 4000ft, while similar high chance probabilities exist above
4,000ft for snowfall totals >30". In the Rockies, high chance
probabilities (>70%) for >12" of snow on Day 1 are present above
5,000ft in the Blue Mountains, Bitterroots, and the Lewis Range,
while those same probabilities for >18" are present above 6,000ft
in the Sawtooth. Snowfall in the Tetons and Wind River Ranges are
likely to range between 1-3 feet with some localized amounts
approaching 4 feet in the more remote reaches of these ranges
including the next round on Sunday. The WSSI is keying in on
Extreme Impact potential (extremely dangerous travel, damages to
infrastructure in the Wind River, Teton, and Absaroka ranges
through Friday night, largely in the higher reaches of these
ranges. Still, Major Impacts (significant travel disruptions) at
intermediate elevations of these ranges are likely with heavy snow
and whiteout conditions contributing to the impacts in these ranges
to close out the week.


...Sierra Nevada...
Days 2-3...

Precipitation along the southern periphery of the AR plume begins
to sink southward towards the central Sierra Nevada by the end of
Day 1, but with snow levels near 9000ft. Multiple AR impulses
through early Monday are expected with snow levels potentially
dropping down to around 8000ft as these moisture plumes are aimed
at the northern/central Sierra Nevada. WPC probabilities for at
least 12 inches of snowfall on days 2-3 (ending 12z Monday) are
between 50-70% and primarily above 9000ft elevation. This is
possibly the start of a very active and impactful weather pattern
across California, with additional high elevation heavy snow likely
through the middle to end of next week.


The probability of significant icing is less than 10 percent.


Snell


$$

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FOUS11 KWBC 190744
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
244 AM EST Fri Dec 19 2025

Valid 12Z Fri Dec 19 2025 - 12Z Mon Dec 22 2025


...Great Lakes & Northern New England...
Days 1-2...

Negatively tilted upper trough and associated strong cold front is
expected to swing across the Great Lakes and East Coast today
producing a rapid drop in temperatures and gusty winds. This setup
will also provide the opportunity for heavy lake effect and upslope
snow. 850 mb temperatures as low as -15C to -20C are expected
behind the strong cold front as lake temperatures remain largely
around 5C. This temperature delta and brief surge of west-
northwesterly flow will allow for heavy lake effect snow in the
typical snowbelts downwind of Lake Superior and Michigan, with
additional heavier snow possible downwind of Lake Erie and Lake
Ontario given the greater westerly component to the low-level
winds. The highest WPC probabilities for at least 6" of snow
through Saturday morning is across the Tug Hill Plateau downwind of
Lake Ontario, where chances sit at 70-90%. Additionally, some
light to moderate upslope post-frontal snowfall is possible along
the central Appalachians and northern New England elevated west-
northwest facing terrain. Here, WPC probabilities for at least 4
inches of snowfall through 18z Saturday range between 30-60%.


...Cascades, Northern Rockies, & Northern California...
Days 1-3...

An anchored -WPO/-PNA teleconnection pattern is the culprit in the
endless barrage of atmospheric rivers and moist Pacific flow into
the western U.S. This will feed copious amounts of snow throughout
the mountains of the Pacific Northwest and stream as far east as
the northern Rockies. The strongest IVT signal shifts southward
over the next few days and focuses over southern Oregon and
especially northern California this weekend. It is within this
moisture plume where the highest snow levels above 8000-9000ft
reside, with much lower snow levels to the north across the Pacific
Northwest on Day 1 around 1000-2000ft. These lower snow levels
also overspread the northern Rockies by the end of Day 1 after
starting in the 5000-6000ft range within the core of the ongoing
Atmospheric River. For the Tetons, Absaroka, and Wind River Ranges,
this region will reside closer to stronger 700mb jet and anomalous
PWATs (>99th ECMWF climatological percentiles through Friday
afternoon), giving these ranges both an abundance of moisture and
strong upslope enhancement to keep heavy snow in the forecast
through Saturday morning for elevation at and above 7000ft. For
northern CA, snow levels dip below 5,000ft in the Siskiyou and
Shasta, but as precipitation also wanes. These levels rise once
again above 6000-7000ft with the next AR on Sunday.

The lone exception to the higher snow levels will be ongoing
westerly upslope flow into the WA Cascades as low pressure lingers
off the coast of British Columbia. Snow levels are also expected to
remain quite low and around 1,500ft on Saturday and 2,500 ft on
Sunday. The bulk of the heaviest snowfall in the WA Cascades and
Olympics is expected above 2500ft. WPC 72-hour probabilities show
high chances probabilities (>70%) for snowfall totals >18" between
3,000- 4000ft, while similar high chance probabilities exist above
4,000ft for snowfall totals >30". In the Rockies, high chance
probabilities (>70%) for >12" of snow on Day 1 are present above
5,000ft in the Blue Mountains, Bitterroots, and the Lewis Range,
while those same probabilities for >18" are present above 6,000ft
in the Sawtooth. Snowfall in the Tetons and Wind River Ranges are
likely to range between 1-3 feet with some localized amounts
approaching 4 feet in the more remote reaches of these ranges
including the next round on Sunday. The WSSI is keying in on
Extreme Impact potential (extremely dangerous travel, damages to
infrastructure in the Wind River, Teton, and Absaroka ranges
through Friday night, largely in the higher reaches of these
ranges. Still, Major Impacts (significant travel disruptions) at
intermediate elevations of these ranges are likely with heavy snow
and whiteout conditions contributing to the impacts in these ranges
to close out the week.


...Sierra Nevada...
Days 2-3...

Precipitation along the southern periphery of the AR plume begins
to sink southward towards the central Sierra Nevada by the end of
Day 1, but with snow levels near 9000ft. Multiple AR impulses
through early Monday are expected with snow levels potentially
dropping down to around 8000ft as these moisture plumes are aimed
at the northern/central Sierra Nevada. WPC probabilities for at
least 12 inches of snowfall on days 2-3 (ending 12z Monday) are
between 50-70% and primarily above 9000ft elevation. This is
possibly the start of a very active and impactful weather pattern
across California, with additional high elevation heavy snow likely
through the middle to end of next week.


The probability of significant icing is less than 10 percent.


Snell





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FOUS11 KWBC 192022
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
322 PM EST Fri Dec 19 2025

Valid 00Z Sat Dec 20 2025 - 00Z Tue Dec 23 2025


...Great Lakes & Northern New England...=20
Days 1-2...

Negatively-tilted upper trough and associated strong cold front=20
will exit New England this evening with a sharp drop in=20
temperatures behind it. 850 mb temperatures as low as -15C to -20C=20
are expected behind the strong cold front as lake temperatures=20
remain largely around 5C. This temperature delta and brief surge of
west- northwesterly flow will support moderate to heavy lake=20
effect snow in the typical snowbelts downwind of Lake Superior and=20
Michigan, with additional heavier snow possible downwind of Lake=20
Erie and especially Lake Ontario given the greater westerly=20
component to the low-level winds. The highest WPC probabilities for
at least 8" of snow through Saturday are across the Tug Hill=20
Plateau downwind of Lake Ontario (70-90%). Additionally, some light
to moderate upslope post-frontal snowfall is possible across=20
northern New England over elevated west-northwest-facing terrain.=20
Here, WPC probabilities for at least 4 inches of snowfall through=20
Saturday range between 40-70%.


*** Atmospheric River to continue in the West into and through next
week ***

...Cascades, Northern Rockies, & Northern California...=20
Days 1-3...

An anchored -WPO/-PNA teleconnection pattern is the culprit in the
endless barrage of atmospheric rivers and moist Pacific flow into=20
the western U.S. This will feed copious amounts of snow throughout=20
the mountains of the Pacific Northwest and stream as far east as=20
the northern Rockies. The strongest IVT signal has shifted=20
southward today and will focus over northern California ENE across=20
the Great Basin to the WY ranges this weekend. It is within this=20
moisture plume where the highest snow levels above 8000-9000ft=20
reside, with much lower snow levels to the north in the colder air=20
mass across the Pacific Northwest (WA into OR) tonight around=20
1000-2000ft. These lower snow levels will continue to overspread=20
the northern and central Rockies tonight/Saturday after starting in
the 5000-7000ft range within the core of the ongoing Atmospheric=20
River. For the Tetons, Absaroka, and Wind River Ranges, this region
will reside closer to stronger 700mb jet and anomalous PWATs/IVT=20

98th climatological percentiles), giving these ranges both an=20

abundance of moisture and strong upslope enhancement to keep heavy=20
snow in the forecast through Saturday morning for elevation at and=20
above 7000ft. For northern CA, snow levels dip below 5,000ft in the
Siskiyou and Shasta, but as precipitation also wanes. These levels
rise once again above 6000-7000ft with the next AR on Sunday.

North of the AR, westerly upslope flow into the WA Cascades will=20
support much lower snow levels -- around 1,500ft on Saturday and=20
2,500 ft on Sunday. The bulk of the heaviest snowfall in the WA=20
Cascades and Olympics is expected above 2500ft, so this will=20
include nearly all the passes (e.g., Snoqualmie). WPC 72-hour=20
probabilities show high chances probabilities (>70%) for snowfall=20
totals >18" between 3000-4000ft, while similar high chance=20
probabilities exist above 4000ft for snowfall totals >30".

In the Rockies, snow will start to lessen tonight over the=20
Tetons/Wind River Range with additional light/modest accumulation=20
Day 1 of several inches, but perhaps more than a foot (>50%=20
probabilities) over the Uintas. For Days 2-3, additional snowfall=20
in the Tetons and Wind River Ranges are likely to range between 1-3
feet with some localized amounts approaching 4 feet in the more=20
remote reaches of these ranges as another surge of moisture=20
associated with the long-lived AR moves through. Major Impacts=20
(significant travel disruptions) are expected. Some light snow is=20
also expected in the CO Rockies tonight into Saturday.

...Sierra Nevada...
Days 1-3...

Precipitation along the southern periphery of the AR plume begins=20
to sink southward towards the central Sierra Nevada tonight, but=20
with snow levels near 9000ft. Multiple AR impulses through Monday=20
are expected with snow levels potentially dropping down to around=20
7500ft as these moisture plumes are aimed at the northern/central=20
Sierra Nevada. This may impact some of the passes across the crest=20
(e.g., Donner Pass at 7239ft) as snow levels dip/oscillate. The AR=20
event will continue beyond this forecast period into the medium=20
range. WPC probabilities for at least 12 inches of snowfall on days
1-3 (ending 00Z Tuesday) are between 50-70% and primarily above=20
9000ft elevation. Snow levels will trend a bit lower into Monday=20
and WPC probabilities for at least 4 inches of snow are >30% to=20
elevations around 7500ft. This is possibly the start of a very=20
active and impactful weather pattern across California, with=20
additional high elevation heavy snow likely through the middle to=20
end of next week. See our latest Key Messages that cover the event=20
through the end of next week, and CPC's Key Messages into week 2.


The probability of significant icing is less than 10 percent.=20


Fracasso/Snell


...Atmospheric River Key Messages are in effect. Please see=20
the link below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!8sYtn0Wp774cnXpWXeT7AtfkTrDIam3_gR8MIUE4ki1Bk= zV6PsnZfiUuTi3j4YSONvYfbDAVkptvoOQj63yLjG5gmDs$=20



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FOUS11 KWBC 200753
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 AM EST Sat Dec 20 2025

Valid 12Z Sat Dec 20 2025 - 12Z Tue Dec 23 2025


...Great Lakes...
Days 1-2...
Maximum impact level from WSSI: Minor

Weather pattern across the Great Lakes quickly shifts away from=20
strong cold air advection as a shortwave crosses over the region=20
with an associated surface low tracking north of Lake Superior=20
towards southern Quebec by Sunday morning. This allows for some=20
moderate warm air advection snow across the Upper Great Lakes=20
followed by lake effect snow overnight behind a potent cold front.=20
This west-northwest flow returns to Lake Ontario and Lake Erie by=20
Sunday as well. All in all snowfall amounts from this system don't=20
appear that impressive given it's progressive nature. WPC=20
probabilities for at least 6 inches of snowfall are highest across=20
the eastern U.P. of MI and between 40-70%. Chances for at least 4=20
inches of snow downwind of Lake Ontario are low (20-40%) along its=20
southern shore and the Tug Hill through Day 2.


...Cascades, Northern Rockies, & Northern California...=20
Days 1-3...
Maximum impact level from WSSI: Major to Extreme

Deep upper troughing in eastern Pacific below the 10th
climatological percentile through at least early next week
continues to allow for an influx of westerly flow and Pacific
moisture into the western U.S. along with increasing IVT within a
wavering Atmospheric River. As moisture flux wanes across the
northern Rockies on Day 1 the next surge enters the region by the
start of Day 2 with snow levels starting around 5000ft across the
Sawtooths before steadily increasing throughout the region,=20
including the Absarokas, Tetons, and Wind River Range, up to=20
around 8000ft within the core of the moisture plume extending all=20
the way back to the central Pacific. Moisture will be plentiful as=20
PWs increasing to above the 99th climatological percentile over=20
northern UT and into WY. The heaviest snowfall is expected=20
throughout the ranges of central ID and western WY. WPC=20
probabilities for at least 18 inches of snowfall through Tuesday=20
morning are high (70-90%) across the Sawtooths of ID and Wind=20 River/Teton/Absaroka ranges of WY above 8000ft. Snowfall totals in=20
this region could top 2 to 3 feet.

Farther north and away from the immediate AR plume, persistent
westerly flow and lower snow levels are forecast to impact the
Pacific Northwest. Snow levels across the Cascades are expected to
start the forecast period around 2000ft and only briefly rise to
around 3000ft tonight before falling yet again to 2000ft on Monday.
This places all major passes at risk of heavy accumulating snowfall
and treacherous driving conditions. Snoqualmie (3022ft) and=20
Stevens Pass (4061ft) of particular note could see total snow=20
accumulations between 1 to 2 feet. WPC probabilities for at least 2
feet of snowfall are high (70-90%) across the WA Cascades above=20
4000ft, with high chances for at least 12 inches of snow above=20
3000ft. Moisture also continues to stream into the northern ID and=20
northwest MT ranges, where elevations above 5000ft have high=20
chances for at least 8 inches of snowfall over a 72-hr period.


*** Strong Atmospheric River to impact California and the Sierra
Nevada through next week ***

...Sierra Nevada...
Days 1-3...
Maximum impact level from WSSI: Major to Extreme

Multiple AR impulses through Tuesday are expected with snow levels
potentially dropping down to around 7500ft as these moisture=20
plumes are aimed at the northern/central Sierra Nevada, with the
strongest surge forecast on Sunday ahead of a strong shortwave.=20
This may impact some of the passes across the crest (e.g., Donner=20
Pass at 7239ft) as snow levels dip/oscillate. The AR event will=20
continue beyond this forecast period into the medium range. WPC=20 probabilities for at least 12 inches of snowfall on days 1-3=20
(ending 12Z Tuesday) are between 70-90% and primarily above 8500ft=20 elevation. Snow levels will trend a bit lower into Monday and=20
Tuesday as WPC probabilities for at least 4 inches of snow are >30%
to elevations around 7500ft. This is possibly the start of a very=20
active and impactful weather pattern across California, with=20
additional high elevation heavy snow likely through the middle to=20
end of next week. See our latest Key Messages that cover the event=20
through the end of next week, and CPC's Key Messages into week 2.


The probability of significant icing is less than 10 percent.=20


Snell



...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!68GdDrL0WuNUm2DNvJV3RZ1kO2Bp3LoaocoX2kDXlLn61= 3QYlpxY-MzlnpzPb72VtZyArvWymtpFbSYDITP7298IFM8$=20



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FOUS11 KWBC 202018
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
318 PM EST Sat Dec 20 2025

Valid 00Z Sun Dec 21 2025 - 00Z Wed Dec 24 2025


...Great Lakes...
Days 1-2... Maximum impact level from WSSI: Minor

Clipper system moving through southern Ontario will bring=20
generally light snow to the Great Lakes via warm air advection=20
first, followed by light to moderate lake effect snow over the U.P.
of Michigan and into the Tug Hill Plateau post-FROPA. Residence=20
time will be on the shorter side, limiting total accumulations=20
Sunday and early Monday. WPC probabilities for at least 6 inches of
snow are highest across the eastern U.P. of MI and between 40-70%.
Chances for at least 4 inches of snow downwind of Lake Ontario are
moderate (40-70%) along its southern shore and the Tug Hill=20
through Day 2.


...Northeast...
Day 3... Probability of at least Minor Impacts: >50%

Jet stream over the northern Plains to the Upper Midwest will help
carry a surface low pressure through southern Canada and a front=20
through the Great Lakes. Broad WAA ahead of the system over the=20
still cold Northeast will bring generally light snow to much of the
Northeast and northern Mid-Atlantic away from the immediate coast.
Some light freezing rain is possible on the southern edge of the=20 precipitation (central PA and perhaps into parts of WV) though the=20
highest QPF will lie over Northern/Upstate/Central NYS at the nose=20
of a 130kt jet through 00Z/Wed. WPC probabilities for at least 4=20
inches of snow are >50% in the Tug Hill (embedded probabilities=20

70%) as well as into the Green Mountains.

...Cascades, Northern Rockies, & Northern California...=20
Days 1-3... Maximum impact level from WSSI: Major to Extreme

Strong west-to-east 160+kt jet into Oregon will lift northward=20
tonight in response to digging heights along 140W. This will=20
maintain light to moderate precipitation over the Cascades and=20
downstream to the Northern Rockies on the cooler side of the=20
Atmospheric River that is positioned over Northern California. Snow
levels will remain on the lower side north of the moisture plume,=20
but continued upslope into the Cascades and Rockies will still=20
yield modest snow totals for these regions, especially days 1-2.=20
The incoming shortwave tomorrow night will briefly raise snow=20
levels in the WA Cascades from around 2000 to 3000ft, but then fall
again with some CAA behind the system. This will continue to=20
impact the passes in the region (e.g., Snoqualmie and Stevens)=20
where significant snow is likely. This may be focused around two=20
waves -- the initial one tonight/tomorrow with another Monday night
into Tuesday. WPC probabilities for at least 12 inches of snow for
the three-day period are >50% above 3000ft or so. Farther east,=20
snow levels around 4000-6000ft over the northern Rockies will rise=20
later tonight as heights rise and moisture increases. SW flow and=20
sufficient moisture will support lighter but still appreciable snow
compared to the Cascade over northern Idaho into northwestern=20
Montana, generally above 5000ft.=20

The strongest moisture flux will be in the core of the AR where PW
and IVT anomalies lie near/above the 99th percentile, generally in
an arc from the southern OR Cascades into the central/southern=20
Idaho ranges and into Wyoming. There, WSW to W flow will maximize=20 accumulations over parts of the Bitterroots and especially into the
Tetons, Absarokas, and Wind River Range. WPC probabilities for at=20
least 24 inches of snow over the three-day period are high (>70%)=20
over western Wyoming. High mountain peaks/ridges above=20
9000-10,000ft may see several feet of snow.=20


*** Strong Atmospheric River to impact California and the Sierra=20
Nevada through next week ***

...Sierra Nevada...
Days 1-3... Maximum impact level from WSSI: Major to Extreme

A long-lived Atmospheric River event will contain waves of=20
precipitation as embedded systems move inland from the Pacific over
the next several days (and beyond). An area of surface low=20
pressure will move inland across NorCal tonight/early Sunday and=20
bring heavier snow to the northern/central Sierra into early Monday
with snow levels around 8000-10,000ft from north to south. Snow=20
may impact some of the passes across the Sierra Crest though the=20
heaviest snow rates may be above 9000ft (2-3"/hr). Thereafter, the=20
moisture plume will lift northward and snow levels may lower a bit=20
into Tuesday with less accumulation overall except for the highest=20
peaks in the Shasta/Siskiyous and farthest north Sierra. This is=20
possibly the start of a very active and impactful weather pattern=20
across California, with additional high elevation heavy snow likely
through the middle to end of next week. See our latest Key=20
Messages that cover the event through the end of next week, and=20
CPC's Key Messages into week 2.


The probability of significant icing is less than 10 percent.=20

Fracasso


...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-8zQPUyCgrJcQnhUCXMvQ3b_nE5Ze81Ok5BTIcxjXD8Py= r7EUaeUp7XWbO2laLsh-nfWXFH7q8lMAJhKbriU0lGuQyc$=20



$$

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FOUS11 KWBC 210754
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
254 AM EST Sun Dec 21 2025

Valid 12Z Sun Dec 21 2025 - 12Z Wed Dec 24 2025


...Upstate New York...
Day 1... Maximum impact level from WSSI: Minor

Clipper system racing across southeast Canada and a strong cold=20
front pushing across the Great Lakes and Northeast will provide the
chances for isolated snow squalls and a heavy lake effect snowband
downwind of Lake Ontario through tonight. Westerly flow around 40
kts at 850 mb and temperatures at this level around -15C will aid a
single snowband off Lake Ontario into Oswego and northern Oneida
counties. Flow bends towards a more northerly direction around 00Z
tonight before the band lifts back north on Monday. This wavering
will prevent significant snowfall accumulations, but moderate=20
amounts are still possible specifically prior to 00Z tonight. WPC=20 probabilities for at least 6 inches of snow are around 30-60% for=20
this region extending east from the southeast shores of Lake=20
Ontario.


...Northeast...
Days 2-3... Probability of at least Minor Impacts: >60%

Upper level pattern over CONUS by late day 2 includes an anomalous
ridge centered over the central U.S. and strong jet soaring to the
north along the U.S-Canadian border before aiming southeastward
across the Northeast, where slight troughing remains. An embedded
shortwave crossing north of the Great Lakes on Tuesday within a=20
divergent left-exit region of a strengthening 150kt jet streak will
aid in blossoming precipitation across the Northeast by Tuesday.=20
Broad WAA ahead of the system over the still cold Northeast will=20
bring generally light snow to much of the Northeast and northern=20
Mid- Atlantic away from the immediate coast as early as Tuesday
morning. Some light freezing rain is also possible on the southern
edge of the precipitation (central PA and perhaps into parts of=20
WV) though the highest QPF will lie over Northern/Upstate/Central=20
NYS to southern New England. Snow is expected to track across New=20
England on day 3 as the shortwave crosses over the region and could
help spin up a surface low in the Gulf of Maine. This may lead to=20
an inverted trough or quickly developing TROWAL maximizing QPF=20
potential across southern Maine, but high uncertainty remains=20
within the day 3 timeframe. WPC probabilities for at least 4 inches
of snow are currently 20-40% from NYS through much of New England=20
(excluding regions south of I-90).=20


...Cascades, Northern Rockies, & Northern California...=20
Days 1-3... Maximum impact level from WSSI: Major to Extreme

Digging heights near 135W in the eastern Pacific will help lift a
shortwave over the Northwest tonight as well as direct a resurgent
Atmospheric River into northern California with spillover=20
extending into the Northern Rockies. Snow levels will remain on the
lower side north of the moisture plume, but continued upslope into
the Cascades and Rockies will still yield modest snow totals for=20
these regions, especially days 1-2. The incoming shortwave tonight=20
will briefly raise snow levels in the WA Cascades from around 2000=20
to 3000ft, but then fall again with some CAA behind the system.=20
This will continue to impact the passes in the region (e.g.,=20
Snoqualmie and Stevens) where significant snow is likely. Heavy=20
snow in these regions of the Northwest and Northern Rockies may be=20
focused around two waves -- the initial one today/tonight with=20
another Monday night into early Tuesday. WPC probabilities for at=20
least 12 inches of snow for the three-day period are >50% above=20
3000ft or so.

Farther east, snow levels around 6000ft over the Northern Rockies=20
will rise today as heights rise and moisture increases. SW flow and
sufficient moisture will support lighter but still appreciable=20
snow compared to the Cascades over northern Idaho into=20
northwestern Montana, generally above 5000ft. The strongest=20
moisture flux will be in the core of the AR where PW and IVT=20
anomalies lie near/above the 99th percentile, generally in an arc=20
from the southern OR Cascades into the central/southern Idaho=20
ranges and into Wyoming. There, WSW to W flow will maximize=20
accumulations over parts of the Bitterroots and especially into the
Tetons, Absarokas, and Wind River Range. WPC probabilities for at=20
least 24 inches of snow over the three-day period are high (>70%)=20
over western Wyoming. High mountain peaks/ridges above=20
9000-10,000ft may see several feet of snow before precipitation
begins to wane on Tuesday.


*** Strong Atmospheric River to impact California and the Sierra
Nevada over the next several days ***

...Sierra Nevada...
Days 1-3... Maximum impact level from WSSI: Major to Extreme

A long-lived Atmospheric River event will contain waves of=20
precipitation as embedded systems move inland from the Pacific over
the next several days (and beyond). An area of surface low=20
pressure will move inland across NorCal today and bring heavier=20
snow to the northern/central Sierra into early Monday with snow=20
levels around 8000-10,000ft from north to south. Snow may impact=20
some of the passes across the Sierra Crest though the heaviest snow
rates may be above 9000ft (2-3"/hr). Thereafter, the moisture=20
plume will lift northward and snow levels may lower a bit into=20
Tuesday with less accumulation overall except for the highest peaks
in the Shasta/Siskiyous and farthest north Sierra. The next surge
of moisture is expected by the end of day 3 as the lingering AR
plume orients more north-south in response to height falls just off
the West Coast. Snow levels also fall with this next round to
around 6000-8000ft from north to south. WPC probabilities for at
least 12 inches of snowfall are 50-90% above around 8000ft through
12z Wednesday. This very active and impactful weather pattern=20
across California is expected to continue through at least the next
several days, with additional high elevation heavy snow likely into
the end of this week. See our latest Key Messages that cover the=20
event through the end of next week, and CPC's Key Messages into=20
week 2.


The probability of significant icing is less than 10 percent.=20

Snell/Fracasso



...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!_FA_POhDFb5HJN-sUJ0i9jl8edjRRHh_SXBYQveL5RWit= qoz7Ca9u2HIoLQ1LcVdJwLI1W3MtAeUtLooha-m7g8eNWg$=20



$$

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FOUS11 KWBC 212011
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
311 PM EST Sun Dec 21 2025

Valid 00Z Mon Dec 22 2025 - 00Z Thu Dec 25 2025


...Upstate/Central New York...
Day 1... Maximum impact level from WSSI: Minor

Exiting trough will lead to an end to any lake effect snow over NY
east of ROC and near/south of Oswego to SYR. Additional snowfall=20
after 00Z tonight will be light, though some areas between Sodus=20
and Oswego could see another 4" of snow where WPC probabilities are

50%.=20

...Northeast...
Days 2-3... Probability of at least Minor Impacts: >70%

Upper level pattern over CONUS by Day 2 includes an anomalous=20
ridge centered over the central U.S. and strong jet soaring to the=20
north along the U.S-Canadian border before aiming southeastward=20
across the Northeast, where slight troughing remains. An embedded=20
shortwave crossing north of the Great Lakes on Tuesday within a=20
divergent left-exit region of a strengthening 150kt jet streak will
aid in blossoming precipitation across the Northeast by early=20
Tuesday. Broad WAA ahead of the system over the still cold=20
Northeast (especially just inland) will bring generally light snow=20
to much of the Northeast and northern Mid-Atlantic but some light=20
freezing rain on the southern edge of the precipitation shield=20
(central PA and perhaps into parts of WV). The highest QPF will lie
over Northern/Upstate/Central NYS into central New England within=20
the zone of strongest lower-level WAA as the surface warm front=20
lifts into the region. With the fast flow, the parent low over=20
Canada will get left behind as the front occludes and stretches=20
across New England, ultimately forming a new low in the Gulf of=20
Maine. This may lead to an inverted trough or quickly developing=20
TROWAL maximizing QPF/snow potential across southern Maine, but=20
uncertainty remains with the details. The system will pull away=20
from eastern New England late Wednesday afternoon and snow will=20
come to an end by the end of this forecast period. WPC=20
probabilities for at least 4 inches of snow are >50% over portions=20
of the Finger Lakes region northward to the Tug Hill and=20
Adirondacks, Green Mountains, and into the Maine Midcoast. The=20
highest probabilities for at least 6 inches of snow are over the=20
Tug Hill/Adirondacks.=20



...Cascades, Northern Rockies, & Northern California...=20
Days 1-3... Maximum impact level from WSSI: Major to Extreme

Digging heights near 135W in the eastern Pacific will help lift a=20
shortwave over the Northwest tonight as well as direct a resurgent=20 Atmospheric River into northern California with spillover extending
into the Northern Rockies. Snow levels will remain on the lower=20
side north of the moisture plume, but continued upslope into the=20
Cascades and northern Rockies will still yield modest snow totals=20
for these regions, especially days 1-2. The incoming shortwave=20
tonight will briefly raise snow levels in the WA Cascades from=20
around 2000 to 3000ft, but then fall again with some CAA behind the
system. This will continue to impact the passes in the region=20
(e.g., Snoqualmie and Stevens) where significant snow is likely.=20
Heavy snow in these regions of the Northwest and Northern Rockies=20
may be focused around two waves -- the initial one tonight with=20
another Monday night into early Tuesday. WPC probabilities for at=20
least 12 inches of snow for the three-day period are >50% above=20
3000ft or so.

Farther east, snow levels around 4000-8000ft over the Northern=20
Rockies (north to south) will rise a bit more tonight in advance of
more snow. SW flow and sufficient moisture will support lighter=20
but still appreciable accumulations compared to the Cascades over=20
northern Idaho into northwestern Montana, generally above 5000ft.=20
The strongest moisture flux will be in the core of the AR where PW=20
and IVT anomalies lie near/above the 99th percentile, generally in=20
an arc from the southern OR Cascades into the central/southern=20
Idaho ranges and into Wyoming. There, WSW to W flow will maximize=20 accumulations over parts of the Bitterroots and especially into the
Tetons, Absarokas, and Wind River Range. WPC probabilities for at=20
least 24 inches of snow over the three-day period are high (>70%)=20
over central Idaho and especially western Wyoming. High mountain=20 peaks/ridges above 9000-10,000ft may see several feet of snow=20
before precipitation begins to wane on Tuesday in response to=20
building heights along/east of the Divide.


*** Strong Atmospheric River to impact California and the Sierra=20
Nevada over the next several days ***

...Sierra Nevada...
Days 1-3... Maximum impact level from WSSI: Major to Extreme

A long-lived Atmospheric River event will contain periods of=20
precipitation as embedded systems move inland from the Pacific over
the next several days (and beyond). A few areas of surface low=20
pressure have and will move inland across NorCal today/tonight and=20
will continue to bring heavier snow to the northern/central Sierra=20
into early Monday with snow levels around 8000-10,000ft from north=20
to south. Snow may impact some of the passes across the Sierra=20
Crest though the heaviest snow rates may be above 9000ft (2-3"/hr).
Monday night/early Tuesday, the moisture plume will lift northward
with less accumulation overall (except for the highest peaks in=20
the Shasta/Siskiyous and farthest north Sierra) as another system=20
in the Pacific deepens. This will allow the initial plume to weaken
a bit over NorCal into southern Oregon while the next surge of=20
moisture pushes into central CA in response to height falls just=20
off the West Coast. This will target most of the Sierra by early=20
Wednesday with increasingly heavier snow and snow rates (2-4"/hr=20
near the Crest) above 8000ft that will fall as the AR progresses=20
slowly southeastward.=20

For days 1-2, WPC probabilities for at least 12 inches of snowfall
are >50% above around 8000ft. For day 3 alone, with the next=20
strong moisture surge, WPC probabilities for at least 12 inches of=20
snow are >50% above 8000ft with >70% probabilities for at least 18=20
inches of snow above 9000ft. This very active and impactful weather
pattern across California is expected to continue through much of=20
this week, with additional high elevation heavy snow likely into=20
the end of this week. See our latest Key Messages that cover the=20
event through the end of next week, and CPC's Key Messages into=20
week 2.


The probability of significant icing is less than 10 percent.=20

Fracasso/Snell

...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!8YxyrDcVV2VjIHL52sTTCq9ZhLfybUScoUs9uTHV_nFoe= rz6D4vv4aCmjAfBzmSyI8UdxqgSYNSrs-zGtj35CF7gC7Q$=20



$$

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FOUS11 KWBC 220827
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
327 AM EST Mon Dec 22 2025

Valid 12Z Mon Dec 22 2025 - 12Z Thu Dec 25 2025


...Northeast...
Days 1-3... Maximum impact level from WSSI: Minor to Moderate

Upper level pattern over CONUS by the end of Day 1 includes an=20
anomalous ridge centered over the central U.S. and strong jet=20
soaring to the north along the U.S-Canadian border before aiming=20 southeastward across the Northeast, where slight troughing remains.
An embedded shortwave crossing north of the Great Lakes on Tuesday
within a divergent left-exit region of a strengthening 150kt jet=20
streak will aid in blossoming precipitation across the Northeast by
early Tuesday. Broad WAA ahead of the system over the still cold=20
Northeast (especially just inland) will bring generally light snow=20
to much of the Northeast and northern Mid-Atlantic, but some light
freezing rain on the southern edge of the precipitation shield=20
(central PA and perhaps into parts of WV). The highest QPF=20
associated with the strongest low-level WAA will lie over=20 Northern/Upstate/Central NYS into central New England as the=20
surface warm front lifts into the region. With the fast flow, the=20
parent low over Canada will get left behind as the front occludes=20
and stretches across New England, ultimately forming a new low in=20
the Gulf of Maine. This will likely lead to a separate and higher=20
maximum in QPF due to an inverted trough or quickly developing=20
TROWAL maximizing snow potential across southern/coastal Maine, but
some uncertainty remains with the details as this trough could=20
still shift somewhat east or southwest along the Gulf of Maine.=20
This setup has the potential to produce a narrow corridor of very=20
heavy snowfall given the strong low- level convergence potential=20
from roughly Portland to Bar Harbor, ME. In fact, the NBM 75th=20
percentile currently sits around 12 inches, highlighting the higher
end potential. The system will pull away from eastern New England=20
late Wednesday afternoon.

WPC probabilities for at least 4 inches of snow are >50% over=20
portions of the Finger Lakes region northward to the Tug Hill and=20 Adirondacks, Green Mountains, and into the White Mountains and=20
Maine Midcoast. The highest probabilities (40-70%) for at least 6=20
inches of snow extend between the southern and midcoasts of
Maine. The National Weather Service in Gray, ME has issued Winter=20
Storm Watches in this region for the potential for total snow=20
accumulations greater than 6 inches. Lighter, festive snowfall is=20
expected elsewhere in New England on Tuesday and even as far south=20
as northeast PA/northern NJ for the Tuesday morning commute.


...Interior West & Rockies...
Days 1 & 3... Maximum impact level from WSSI: Moderate to Major

Heavy snowfall continues to impact the high terrain of the Rockies
and Intermountain West, but will see the overarching pattern begin
to shift away from the recent west-east oriented Atmospheric River
spillover towards more southerly flow and approaching height falls
by midweek. With that said, the Day 1 period starts with the
aforementioned AR and anomalous PWs extending from the northern
Sierra Nevada into the Northern Rockies, but this moisture stream
is expected to wane today as an associated shortwave ejects
eastward with ridging building in its place across the Rockies
through Tuesday. Snow levels will remain high within the axis of
greatest precipitation located across central ID into southwest MT
and western WY, with levels generally in the 7000-8000ft range. The
most impact snowfall with amounts measured in feet continue to be
located across the Wind River Range, Tetons, and Absarokas.

A brief lull in heavy snowfall is expected on Tuesday as IVT
weakens and reorients into a more north-south direction into the
northern Great Basin as height falls approach the West Coast.
However, by Day 3 a broad surge of tropical moisture lifts
throughout the interior West due to a near-record deep upper trough
off the West Coast. Given the moisture source it isn't too
surprising that snow levels across the Great Basin and Rockies will
be rather high, above 9000ft in Utah and above 10,000ft in western
Colorado, with slightly lower values around 7000-8000ft in the
Northern Rockies during this time period.

WPC 72-hr snowfall probabilities for at least 12 inches of snow are
highest across the Sawtooths of ID and Wind River/Absarokas of WY,
with 70-90% chances mainly above 8500ft.


*** Strong Atmospheric River to impact California and the Sierra=20
Nevada over the next several days ***

...Sierra Nevada/Northern California/Cascades...
Days 1-3... Maximum impact level from WSSI: Major to Extreme

A long-lived Atmospheric River event will contain periods of=20
precipitation as embedded systems move inland from the Pacific over
the next several days (and beyond). For Day 1 (ending 12Z Tuesday),
the ongoing AR will lift north into northern CA and weaken with
limited snowfall impacts across CA. Meanwhile, much lower snow
levels and a potent shortwave entering southeast British Columbia
will allow for heavy snow across the Olympics and Cascades today
into early Tuesday. Here, snow levels will vary between
1500-2000ft, which puts accumulating snow below the major WA
Cascade passes.

By late Day 2 into Day 3, the next surge of moisture impacts the
West Coast and continues beyond into late this week. Deepening
height falls off the West Coast and a potent shortwave lifting on
the eastern periphery of this deep upper trough rapidly surges
moisture inland Tuesday night. IVT directed into the Sierra will be
strong (>800 kg/m/s) Tuesday night, but relatively short-lived as
broad onshore flow and moderate precipitation continues on Day 3.
Snow levels during this strong AR are expected to generally remain
around 8000ft (closer to 8500ft in the core of the AR across the central/southern Sierra Nevada), but quickly fall to between
5000-6500ft (lower north and higher south) across CA on Day 3.=20
This will allow for heavy snow to impact all major passes by=20
Wednesday.

For the most impactful day (Day 3) WPC probabilities for at least=20
12 inches of snowfall are 70-99% above around 7000ft and >70% for=20
at least 24 inches of snowfall above 8000ft in the Sierra Nevada.=20
Strong winds combined with very heavy-wet snowfall could make=20
travel difficult to impossible at times in the high terrain of the=20
Sierra Nevada, with damage to infrastructure also possible. This=20
very active and impactful weather pattern across California is=20
expected to continue through much of this week, with additional=20
high elevation heavy snow likely into the end of this week. See our
latest Key Messages that cover the event through the end of next=20
week, and CPC's Key Messages into week 2.


The probability of significant icing is less than 10 percent.=20

Snell


...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4Zad0Gdrr51OXkfTGAdILviKN5pcYLPC0kOOau9ldhSpK= c8rBebO9pfTYNjHgGi_HaSZmFTnH2fhUaUDCBGGcnbudQc$=20



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FOUS11 KWBC 222058
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
358 PM EST Mon Dec 22 2025

Valid 00Z Tue Dec 23 2025 - 00Z Fri Dec 26 2025

*** Strong Atmospheric River followed by low pressure systems to=20
impact California and the Sierra Nevada through Friday ***


...Northeast...
Days 1-2... Maximum impact level from WSSI: Moderate

A shortwave trough crosses northern Ontario Tuesday and New England
Tuesday night on a potent 150+kt NWly jet below a deep and
sprawling vortex centered north of Hudson Bay. Precip blossoms=20
late tonight in warm air advection over the upper Ohio Valley and
the Northeast Tuesday. Day 1 snow probs for >4" are 30-60% for the
Catskills west toward the Finger Lakes and the southern slopes of
the Adirondacks. Light freezing rain (a few hundredths accretion)=20
on the southern edge of the precipitation shield (from central PA=20
to central WV) is possible late tonight into Tuesday morning.=20

The surface low crosses New England Tuesday evening with continued
snow for Tuesday night in terrain including the Whites, Greens and
Adirondacks as the WAA pivots to deformation banding with=20
topographic enhancement (which should boost snow rates into the=20
1"/hr range) on the back side of the low. Day 1.5 snow probs for=20

6" are 30-80% over this terrain with 50% probs for over 8" in the=20

highest terrain.=20

Most of Maine is north of the surface low track which will have=20
ocean enhanced snow Tuesday night before the back side banding=20
shifts down the coast to produce ocean enhanced snow for eastern=20
Mass Wednesday morning. Day 2 probs for >6" are 40-70% for much of
the central Maine coast west well into the remote interior
portions of the state.


...California/Sierra Nevada...=20
Days 2-3... Maximum impact level from WSSI: Extreme

Atmospheric River (AR) over northern CA this afternoon pivots north
to OR and the northern Rockies tonight. High snow levels over
8000ft lift north with the core of highest precip from the
northern Sierra Nevada through the CA Cascades/Trinity Alps keeping
Day 1 quiet in CA from a snow perspective.=20

However, the now north-south oriented AR pushes across the CA coast
late Tuesday, reaching the full extent of the Sierra Nevada with=20
heavy precip and snow levels around 7000ft Tuesday evening with
particularly heavy snow starting roughly after midnight (with rates
exceeding 3"/hr per the 12Z HREF) above the snow level. Snow=20
levels drop under height falls from the approach trough through the
day Wednesday, though precip rates decrease on the Sierra Nevada=20
as the AR focuses over southern CA with 9000ft snow levels for the=20
SoCal ranges. Day 2 snow probs for >18" are 40% for the higher
central Sierra and 70-100% for the southern Sierra and the highest
White Mtns along the border with NV.

Expect a lull in Sierra Nevada snow Wednesday night as the dry=20
slot works its way across. However, by Thursday rates increase
again ahead of the upper trough axis. This time snow levels are
around 6000ft on the Sierra Nevada under the lower heights of an
upper low centered off northern CA. Snow rates of 2"/hr or more can
be expected for much of Thursday. Broader coverage of the >18"=20
snow probs are depicted for Day 3 with 50-90% values along the full
length of the Sierra Nevada as well as the CA Cascades including=20
Donner Pass on I-80.


Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below. CPC has further=20
KMs for next week.


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Major

Upper low that is directing AR into CA is centered over the Queen
Charlotte Sound (BC) and a reinforcing shortwave trough crosses
Vancouver Island by this evening bringing a round of moderate
precip to the WA Cascades this evening. Snow levels already down
around 2500ft drop to around 1800ft before rates decrease overnight
providing impactful snow well below pass level. Day 1 snow probs
for >6" are 40-60% roughly at pass level in western WA, but it's
really all for this evening.=20

AR across northern CA to western WY this afternoon pivots=20
north to southern OR to the Bitterroots through Tuesday. Snow
levels rise in this moisture axis to around 7000ft keeping Day 1
snow probs for >6" limited to the highest Sawtooths, Tetons, and=20
Absarokas. The AR continues to pivot north-south along the West=20
Coast through Tuesday night with snow levels rising above 4000ft on
the WA Cascades by Wednesday. Day 2 snow probs for >4" are 40-60%=20
in the WA Cascades.

The focus for precip shifts interior on Wednesday as the AR
extending the length of CA shifts east over the Great Basin and the
Rockies for Wednesday night/Thursday. Snow levels are generally
high, 8000-9000ft with this moisture shield shifting inland. Day 3
snow probs for >6" are limited to the highest Great Basin ranges,
the Sawtooths, Uinta, Wind River, and San Juans where values are
40-70% (80% or greater for the higher Wind Rivers).=20


Jackson



...Atmospheric River/Winter Storm Key Messages are in effect for
California as linked below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-VZ02Vbi2p7uqvUSbXIOQH-rdR7tvmWmepI6Nz0W1prv3= DGPmRKbpBHln8TEYs5vFPhnIwL8EQ9CGVhJtRgt-JyXbTM$=20



$$

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FOUS11 KWBC 230833
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
333 AM EST Tue Dec 23 2025

Valid 12Z Tue Dec 23 2025 - 12Z Fri Dec 26 2025

*** Strong Atmospheric River followed by low pressure systems to
impact California and the Sierra Nevada through Friday ***


...Northeast...
Days 1-2... Maximum impact level from WSSI: Moderate

A shortwave trough crosses northern Ontario today and New England=20
early Wednesday on a potent 150+kt NWly jet below a deep and=20
sprawling vortex centered north of Hudson Bay. Precip will be
ongoing this morning in warm air advection over the upper Ohio=20
Valley and the Northeast. Surface temperatures become marginal
quickly after sunrise and limits the potential for heavy
accumulations from PA to southern New England. Light freezing rain
(a few hundredths accretion) is also possible this morning on the=20
southern edge of the precipitation shield (from central PA to=20
central WV).

The surface low crosses New England this evening with continued=20
snow into Wednesday morning for the terrain including the Whites,=20
Greens and Adirondacks as the WAA pivots to deformation banding=20
with topographic enhancement (which should boost snow rates into=20
the 1"/hr range) on the back side of the low. Day 1 snow probs for

6" are 40-80% over this terrain with 50% probs for over 8" in the

highest terrain.=20

Heaviest snowfall associated with this system is expected across
the coastal plain and areas just inland across Maine as low
pressure redevelops along a surface trough over the Gulf of Maine.
This surface trough, or also referred to as a "Norlun Trough", will
lead to very strong and narrow low-level convergence capable of
producing snowfall rates of 1-2"/hr. However, given the narrow axis
these setups can be extremely tricky to forecast. Current
expectations are for heavy snow to occur between Portland and Bar
Harbor, along with areas just inland. Surface temperatures could
also be a concern for regions right along the coast as southerly=20
flow draws both moisture and a slightly warmer marine airmass. Days
1-2 probs for >8" are 50-80% for much of the central Maine coast=20
west well into the remote interior portions of the state. Maximum
amounts within the heaviest band are likely to exceed a foot, which
is depicted in the NBM 75th percentile for areas just inland of the
coastal plain.


...Great Lakes...
Day 3... Chances of at least minor impacts from WSSI-P: 40-50%

By late in the forecast period (Thursday night), the next shortwave
to round the top of the anomalous central U.S. upper ridge begins
to cross over the Northern Plains and Upper Midwest. Even though
the system is fairly unorganized through early Friday morning, the
origins of the shortwave and associated mid-to-upper level moisture
trace back to the tropical Pacific and Atmospheric River set to
impact California. In fact, NAEFS ESAT depict IVT above the 99.5th climatological percentile Thursday evening over the western Great
Lakes. Still, the greatest forcing at this time appears along the
MN-Canadian border and just north into Canada, limiting snowfall
impacts. However, a potent warm nose around 800mb per model cross
sections will allow for precipitation throughout parts of the=20
Upper Midwest and Great Lakes to fall as sleet or freezing rain. As
850mb FGEN rapidly strengthens across southern MI Friday morning=20
in response to a developing low pressure center over the Midwest,
precipitation is expected to blossom and fall mostly as sleet or
freezing rain. WPC probabilities for at least 0.1" of ice accretion
through 12Z Friday (more possible afterwards as well) are currently
low (10-20%) across the central L.P. of MI. Expect higher chances
once all of Friday is in the forecast period.


...California/Sierra Nevada...=20
Days 1-3... Maximum impact level from WSSI: Extreme

Strong Atmospheric River is set to impact CA during the Day 1
period with heavy snowfall across the Sierra Nevada. Additional
systems containing heavy high elevation snow and falling snow
levels are expected through the end of the week. In total, multiple
feet of snowfall are expected along the entire Sierra Nevada
(heaviest in central and southern sections), with snowfall also
impacting most major passes into northern CA.

The meteorological setup for this significant event includes a
currently north-south oriented AR combining with a potent shortwave
lifting along the WEst Coast today while on the eastern periphery
of an anomalous eastern Pacific upper trough. This shortwave and
associated potent surface low pressure will draw moisture northward
out of the tropics and produce IVT above the climatological record
for late December according to the NAEFS ESAT by early Wednesday.=20 Additionally, snow levels start out Tuesday night between
7500-8500ft across CA (highest in the southern Sierra) and fall to
below 6000ft in northern CA by Wednesday night as levels dip to
around 7500ft in the southern Sierra. Where snow does occur across
the Sierra Nevada it will come down extremely heavy as 00z HREF
depicts rates greater than 2-3"/hr after 09Z Wednesday and lasting
into Wednesday evening. Snow levels continue to drop under height=20
falls from the approaching trough through Wednesday night into=20
Thursday though as precip rates decrease on the Sierra Nevada as=20
the AR focuses over southern CA with 9000ft snow levels for the=20
SoCal ranges. This will lead to a dry slow until the next surge
ahead of a separate Pacific low approaches on Thursday.

By Thursday rates increase again ahead of the upper trough axis.=20
This time snow levels are around 6000ft on the Sierra Nevada under=20
the lower heights of an upper low centered off northern CA. Snow=20
rates of 2"/hr or more can be expected for much of Thursday.=20
Broader coverage of the >18" snow probs are depicted for Day 3 with
50-90% values along the full length of the Sierra Nevada as well=20
as the CA Cascades including Donner Pass on I-80. Snow levels also
drop to around 4000ft by the end of Day 3 across northern CA and
allow for accumulating snow potential for the I-5 pass near Mount
Shasta. 72-hr snow probabilities for >30" snow are between 50-90%=20
for much of the Sierra Nevada. Totals are likely to exceed 4-8 feet
above 7000-8000ft.


Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below. CPC has further=20
KMs for next week.


...Pacific Northwest, Great Basin and Rockies...=20
Days 2-3... Maximum impact level from WSSI: Moderate=20

Outside of light snow across the northern Great Basin and Cascades
on Day 1, the next surge of moisture is forecast to enter the
interior West and Northwest ranges on days 2-3. The strong AR=20
extending the length of CA shifts east over the Great Basin and the
Rockies for Wednesday night/Thursday along with its anomalous
moisture. Snow levels are generally high, 8000-9000ft with this=20
moisture shield shifting inland outside of the Cascades where=20
levels increase to 5000ft Wednesday and drop back to around 3000ft=20
Thursday. Days 2-3 snow probs for >6" are limited to the highest=20
OR/WA Cascades, Great Basin ranges, the Sawtooths, Uinta, Wind=20
River, and San Juans where values are 40-70% (80% or greater for=20
the higher Wind Rivers and Sawtooths).=20


Snell/Jackson




...Atmospheric River Key Messages are in effect. Please see=20
current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-I0_CPZ0UePHURDQNcl63Rb55rx8NtluQA6D4C_6vmtRL= qm2ELNT0ODX-yKMq99rSkPeDFD40nbB7L0gE6JKjNo8YlM$=20



$$

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FOUS11 KWBC 231852
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
152 PM EST Tue Dec 23 2025

Valid 00Z Wed Dec 24 2025 - 00Z Sat Dec 27 2025

*** Strong Atmospheric River followed by low pressure systems to
impact California and the Sierra Nevada through Friday ***


...Northeast...
Days 1 & 3-3.5... Maximum impact level from Day 1 WSSI: Major. Day
3-3.5 WSSI-P Minor Maximum Probabilities: 90%.

A sharpening 500mb shortwave trough in southern Ontario heads towards
the Northeast U.S. this afternoon as the diffluent left-exit region
of a roaring 150kt 300mb jet streak adds healthy divergence atop
the atmosphere. A ribbon of 850-700mb WAA and resulting FGEN is
responsible for the ongoing shield of snow across the Northeast
today and, once it becomes quasi-stationary over eastern MA on
north to the Gulf of Maine, will become the defacto train-tracks
for the 850mb low as it tracks from the St. Lawrence Valley tonight
to off the MA Capes by Christmas Eve morning. Periods of snow will
continue, falling heavily at times tonight, from the Adirondacks=20
and the rest of the northern New England mountains, on east to the=20
coast of Maine as the 850mb low strengthens and a Nor-lun trough fosters
heavy snow north and east of Portland. Burst of heavy snow cannot=20
be ruled out as far south as the MA Capes on Wednesday, but the=20
deepening storm system south of Nova Scotia will quickly race east=20
and all but end any accumulating snowfall by mid-afternoon. WPC=20 probabilities show east-central ME as having >50% odds for snowfall
totals >8" through Wednesday afternoon. The WSSI generally shows=20
Moderate Impacts from the Portland area on north and east along the east-central ME coast with localized Major Impacts in areas where
snowfall totals exceed 12". WPC probabilities also depict high=20
chances (>70%) for snowfall totals >4" in portions of the=20
Adirondacks, Green, and White Mountains, as well as much of=20
interior ME. WSSI shows widespread Minor Impacts from this=20
snowfall, implying some inconveniences to travel are likely with=20
winter driving conditions. Those traveling today and Christmas Eve=20
in the interior Northeast should use caution while driving in these
areas.

In wake of a fast moving clipper system over northern New England
on Christmas Day, strong 850mb CAA ahead of a strengthening dome of
Canadian high pressure will result in a cold-air-damming signature
(CAD) to become positioned briefly over the Northeast by Friday
morning. To the west, a progressive 500mb shortwave trough over the
Great Lakes will approach and strong 850mb WAA will accompany
sufficient 290K isentropic ascent to produce precipitation over the
Northeast. Healthy mid-to-upper level ascent will also be supplied
in the form of healthy 700mb Q-vector convergence Friday afternoon
and evening. This classic "over-running" setup with a burgeoning
warm nose of >0C air at low-levels but sub-freezing wet-bulb
temperatures at the surface (due to a cold and very dry boundary
layer at the onset) will allow for an icy wintry mix of
sleet/freezing rain to fall from western PA and northern MD on east
across southern PA and towards the Delaware Valley. Meanwhile,
areas farther north of the storm track and areas with more=20
elevation; such as northern PA, the Poconos, NY Finger lakes,
Catskills, northern NJ, and potentially the NYC metro on north and
east through southern New England, are showing better odds of
remaining mostly snow for Friday afternoon and into Friday night.

Through 12Z Saturday, WPC probabilities show low-to-moderate chances
(20-50%) for snowfall totals >4" in northeast PA, southern NY,=20
northern NJ, western MA, and western CT. Meanwhile, WPC ice=20
probabilities show moderate-to-high chances (50-70%) for ice=20
accumulations over a tenth of an inch along the Laurel Highlands=20
and central Appalachians. The same mountain ranges also show
moderate chances (>50%) for ice accumulations greater than a
quarter inch. Light ice accumulations and some accumulating sleet
is expected as far east as northern MD, southern PA, and the
DC/Baltimore metro areas. There remains ongoing fluctuations in=20
the forecast track which could result in additional changes in=20
which areas see the most snow and ice. Regardless, WPC's WSSI-P=20
show >50% odds for Minor Impacts from western PA to as far east as=20
the Tri-State area between 1AM Fri - 1AM Sat. Residents and=20
travelers following Christmas will want to keep a close eye on this
forecast over the next couple of days.


...Great Lakes...
Days 2.5-3... Maximum chances of at least minor impacts from=20
WSSI-P: 70%

An impressive plume of Pacific and subtropical moisture ejecting=20
out of the robust longwave trough off the West Coast will travel=20
around the northern periphery of the ridge axis over the south-
central U.S. and head for the Great Lakes on Thursday. Guidance is
in agreement on strong 850-700mb WAA over the north-central U.S.
Thursday afternoon with a band of snow developing along the 700mb
front. This is likely to result in a combination of snow and some
embedded sleet/freezing rain across northern ND and northern MN
Thursday night, then across northern WI and the U.P. of MI early
Friday morning. The strong but transient 850-700mb WAA will cause a
stout warm-nose of >0C temperatures over MI that cause a wintry mix
to engulf much of Michigan's Mitten on Friday, with the same icy
potential just east of Lakes Erie and Ontario Friday afternoon. The
progressive nature of this disturbance will help to cap snowfall
totals to generally <4", with the lone exceptions being the MN=20
Arrowhead and northern half of MI's U.P. where WPC probabilities=20
how low-to-moerate chances (20-50%) for snowfall totals >4".
Otherwise, ice is of concern across central and southern MI,
northeast OH, northwest PA, and far eastern NY. WPC probabilities
show moderate-to-high chances (50-70%) for ice accumulations of at
least one-tenth of an inch in these areas on Friday, including the
greater Detroit metro area. There are also low-chance
probabilities, of a more impactful event with over one-quarter of
an inch. WSSI-P shows the tip of the MN Arrowhead having moderate=20
chances (40-60%) for at least Minor Impacts due to snowfall from=20
this system, while central and southern MI sport moderate-to-high=20
chances (50-70%) for Minor Impacts due to ice.


...California/Sierra Nevada...=20
Days 1-3... Maximum impact level from WSSI: Extreme

The next Atmospheric River (AR) pushes across the CA coast
tonight, with heavy precipitation suddenly reaching the=20
central/southern Sierra Nevada around midnight with 3-4"/hr rates
(per the 12Z HREF) above the snow levels of 7500ft/8500ft through=20
the heaviest precip Wednesday morning. Snow becomes more showery=20
with moderate rates and lower snow levels of 6500/7500ft Wednesday=20 afternoon/night in the continued southerly flow behind the main AR=20
plume. The next moisture plume arrives early Thursday morning with=20
snow levels around 6000ft and heavy snow rates of 2-3"/hr into the=20
afternoon before rates decreased a bit in showery conditions and=20
snow levels dipping below 5000ft through Friday morning.=20

These rounds of heavy snow with lowering snow levels will lead to=20
increasing travel and infrastructure impacts. Storm total snowfall=20
in excess of 4ft can be expected above 6500ft along the extent of=20
the Sierra Nevada.

Far northern CA ranges (Shasta Siskiyou/Klamath/etc) can expect
heavy snow above 7000ft tonight and above 5000ft Wednesday
afternoon through Thursday. Moderate snow above 4000ft can be
expected Thursday night through Friday as low pressure lingers near
Cape Mendocino. Some snow impacts to I-5 near Mt Shasta are
possible.

Snow levels remain around 10,000ft in Southern CA through the main
AR plume Wednesday before dropping to around 7000ft Wednesday night
into Friday. Impactful snow looks to remain higher than Big Bear
Lake.=20


Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below. CPC has Key
Messages for the Pacific Northwest into California through early=20
January.


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate=20

The remnant first AR, with an axis from far northern CA to western
MT this afternoon, continues lifting north as surface low pressure
rides along from SW OR up the Cascades tonight into Wednesday. Snow
levels rise on the WA Cascades from around 3000ft this evening to
4000ft by 12Z Wednesday. Moderate snow rates around 0.5"/hr can be
expected through Wednesday morning above those snow levels on the=20
WA Cascades. Day 1 PWPF for >4" above pass level are 40-80%.=20

The next AR surges through CA tonight and across the Great Basin
Wednesday, reaching the western Rockies Wednesday night. Snow=20
levels are high in this moisture shield, 8000-9000ft over the Great
Basin and the Rockies through central ID and WY with much lower=20
precip and snow levels of 6000-7000ft in northern ID and MT. Day=20
1.5 snow probs for >6" are 40-80% in the highest central NV ranges,
the Sawtooths, Wind Rivers, and Uintas.=20

The following moisture surge through CA Thursday brings widespread
precip at lower rates than before across the Great Basin and=20
western Rockies with lower snow levels around 6000-7000ft. Day 2.5
snow probs for >6" are 30-70% again for the highest central NV ranges,
the Sawtooths, Wind Rivers, Uintas, as well as western CO ranges
and the Absarokas.

The upper trough comes ashore Friday in northern CA up through the
PacNW with moderate precip rates and Cascades snow levels around=20
2500ft in WA and 3500ft in OR. Day 3 snow probs for >6" are 40-70%
in the WA Cascades, including Snoqualmie Pass, and around 30% for
the OR Cascades including Santiam Pass. Snow will continue in
earnest for the Rockies into Saturday.


Mullinax/Jackson



...Winter Storm/Atmospheric River Key Messages are in effect and
linked below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!748M92R3xI_pv1iK1Rxjk-4CcKjFg89ad5izP-Qu4FuJA= U0nVasQbx7qHo4hN9wCFbI8WQwj7qA1HBLzwHvxS0diFjc$=20



$$

=3D =3D =3D
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FOUS11 KWBC 240846
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
346 AM EST Wed Dec 24 2025

Valid 12Z Wed Dec 24 2025 - 12Z Sat Dec 27 2025

*** Strong Atmospheric River followed by low pressure systems to
impact California and the Sierra Nevada through Friday ***


...Maine...
Day 1... Maximum impact level from WSSI: Moderate

Heavy snow is expected to continue from overnight along a narrow=20
section of the Midcoast and interior sections of Maine for the=20
first part of Day 1 as a surface (Norlun) trough remains in place.=20
Over 6 inches of snow had already been reported within this band=20
over the coastal plains northeast of Portland as of 05Z. Heavy=20
snowfall with rates around 1-2"/hr are expected to continue through
at least 15Z as this mesoscale areas of low pressure form and=20
pivot within this surface trough. Once this area of low pressure=20
begins pivoting southward, snowfall should quickly ease in=20
intensity. WPC probabilities for an additional 4 inches of snow=20
after 12Z today are 20-40% from Portland east along the Midcoast,
but not after upwards of a foot of storm total snowfall occurs
across the region.


...Great Lakes to Northeast...
Days 2-3... Maximum impact level from WSSI: Moderate

An impressive plume of Pacific and subtropical moisture ejecting=20
out of the robust longwave trough off the West Coast will travel=20
around the northern periphery of the ridge axis over the south-
central U.S. and head for the Great Lakes Thursday night before
reaching the northern Mid-Atlantic/Northeast on Friday-Friday
night. Guidance is in agreement on strong 850-700mb WAA over the=20
north- central U.S. Thursday afternoon with a band of snow=20
developing along the 700mb front. This is likely to result in a=20
combination of snow and some embedded sleet/freezing rain across=20
northern ND and northern MN Thursday night, then across northern WI
and the U.P. of MI early Friday morning. The strong but transient=20
850-700mb WAA will cause a stout warm-nose of >0C temperatures over
MI that cause a wintry mix to engulf much of Michigan's Mitten on=20
Friday, with the same icy potential just east of Lakes Erie and=20
Ontario Friday afternoon. The progressive nature of this=20
disturbance will help to cap snowfall totals to generally <4", with
the lone exceptions being the MN Arrowhead and northern half of=20
MI's U.P. where WPC probabilities show moderate chances (40-70%)=20
for snowfall totals >4". Otherwise, ice is of concern across=20
central and southern MI, where WPC probabilities show moderate-to-=20
high chances (50-80%) for ice accumulations of at least one-tenth=20
of an inch in these areas on Friday, including the greater Detroit=20
metro area. There are also up to 40% chances for a more impactful=20
event with over one- quarter of an inch.

In wake of a fast moving clipper system over northern New England
on Christmas Day, strong 850mb CAA ahead of a strengthening dome of
Canadian high pressure will result in a cold-air-damming signature
(CAD) to become positioned briefly over the Northeast by Friday
morning. To the west, a progressive 500mb shortwave trough over the
Great Lakes will approach and strong 850mb WAA will accompany
sufficient 290K isentropic ascent to produce precipitation over the
Northeast. Healthy mid-to-upper level ascent will also be supplied
in the form of healthy 700mb Q-vector convergence Friday afternoon
and evening. This classic "over-running" setup with a burgeoning
warm nose of >0C air at low-levels but sub-freezing wet-bulb
temperatures at the surface (due to a cold and very dry boundary
layer at the onset) will allow for an icy wintry mix of
sleet/freezing rain to fall from western PA and northern MD on east
across southern PA and towards the Delaware Valley. Given the warm
nose elevated in model cross sections to around 800-750mb, a deep
cold layer below it could mean precipitation falling mostly as
sleet across the northern mid-Atlantic (northern MD,
southern/central PA, and into southern/central NJ). This may cut
down on snowfall and freezing rain accumulations here, but still
could lead to slippery travel. Meanwhile, areas farther north of=20
the storm track and areas with more elevation; such as northern PA,
the Poconos, NY Finger lakes, Catskills, northern NJ, and=20
potentially the NYC metro on north and east through southern New=20
England, are showing better odds of remaining mostly snow for=20
Friday afternoon and into Friday night.

Through 12Z Saturday, WPC probabilities show moderate chances=20
(40-70%) for snowfall totals >4" in northeast PA, southern NY,=20
northern NJ, western MA, and western CT. Greatest chances for at
least 6" of snowfall (30-50%) are across the Poconos and Catskills
of northeast PA and NY. Meanwhile, WPC ice probabilities show=20
moderate chances (50-70%) for ice accumulations over a quarter of=20
an inch along the Laurel Highlands and central Appalachians. This=20
amount of ice would have the potential to produce scattered tree=20
damage and power outages. Light ice accumulations and some=20
accumulating sleet is expected as far east as northern MD, southern
PA, and the DC/Baltimore metro areas. The Philadelphia metro could
see more snow than sleet/freezing rain, but some wintry mix=20
combination can be expected with high uncertainty on amounts at the
moment. There remains ongoing fluctuations in the forecast track=20
which could result in additional changes in which areas see the=20
most snow and ice. Regardless, WPC's WSSI-P show >50% odds for=20
Minor Impacts across a large region from western PA to as far east=20
as the Tri- State area between 1AM Fri - 1AM Sat. Residents and=20
travelers following Christmas will want to keep a close eye on this
forecast over the next couple of days.


...California/Sierra Nevada...=20
Days 1-3... Maximum impact level from WSSI: Extreme

The next strong and quick-hitting Atmospheric River (AR) is=20
entering CA early this morning, with heavy precipitation ongoing=20
across the central/southern Sierra Nevada by 12Z with 3-4"/hr rates
(per the 00Z HREF) above the snow levels of 7500ft/8500ft through=20
the heaviest precip midday today. Snow becomes more showery with=20
moderate rates and lower snow levels of 6500/7500ft Wednesday=20
evening/night in the continued southerly flow behind the main AR=20
plume. The next moisture plume arrives early Thursday morning with=20
snow levels around 6000ft and heavy snow rates of 2-3"/hr into the=20
afternoon before rates decreased a bit in showery conditions and=20
snow levels dipping below 5000ft through Friday morning.
Precipitation is expected to finally wane by Friday night into
early Saturday morning as upper-level ridging builds into the
eastern Pacific and the meandering upper low over CA weakens into a positively-tilted trough extending across the Great Basin.

These rounds of heavy snow with lowering snow levels through Friday
will lead to increasing travel and infrastructure impacts. Storm=20
total snowfall in excess of 4ft can be expected above 6500ft along=20
the extent of the Sierra Nevada.

Far northern CA ranges (Shasta Siskiyou/Klamath/etc) can expect
heavy snow above 5000ft this afternoon through Thursday. Moderate=20
snow above 4000ft can be expected Thursday night through Friday as=20
low pressure lingers near Cape Mendocino. Some snow impacts to I-5=20
near Mt Shasta are possible.

Snow levels remain around 10,000ft in Southern CA through the main
AR plume Wednesday before dropping to around 7000ft Wednesday night
into Friday. Impactful snow looks to remain higher than Big Bear
Lake.=20


Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below.


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Area of low pressure riding up the Pacific Northwest coastline
today will bring a surge of moisture and increasing snow levels.=20
Snow levels rise on the WA Cascades to 5000ft by 12Z this morning
and quickly fall back to around 3500ft by tonight, but also as
moderate precipitation ends. Moderate snow rates around 0.5"/hr=20
can still be expected through this morning above those snow levels
on the WA Cascades.

The aforementioned strong AR surging through CA and will also=20
spill into the Great Basin today, reaching the western Rockies=20
tonight. Snow levels are high in this moisture shield, 8000-9000ft=20
over the Great Basin and the Rockies through central ID and WY with
much lower precip and snow levels of 6000-7000ft in northern ID=20
and MT. Day 1 snow probs for >6" are 40-80% in the highest central=20
NV ranges, the Sawtooths, Wind Rivers, and Uintas.=20

The following moisture surge through CA Thursday brings widespread
precip at lower rates than before across the Great Basin and=20
western Rockies with lower snow levels around 6000-7000ft. Day 2=20
snow probs for >6" are 30-70% again for the highest central NV=20
ranges, the Sawtooths, Wind Rivers, Uintas, as well as western CO=20
ranges and the Absarokas.

The upper trough comes ashore Friday in northern CA up through the
PacNW with moderate precip rates and Cascades snow levels around=20
2500ft in WA and 3500ft in OR. Day 3 snow probs for >6" are 40-70%
in the WA Cascades, including Snoqualmie Pass, and around 30% for
the OR Cascades including Santiam Pass. Snow levels also fall
across much of the Great Basin and Rockies, with levels below
3000-4000ft in the northern Rockies and 5000-7000ft in the central
Great Basin and remaining around 7000ft in the central Rockies.
This allows for more widespread moderate snowfall from the ranges
of northern ID and northwest MT to northern UT, where WPC
probabilities on day 3 for >6" are 50-80% above the aforementioned
snow levels.


...North-Central Montana...
Days 1-1.5... Maximum impact level from WSSI: Minor

Freezing rain is likely and may exceed 0.1" across parts of north-
central MT the night of Christmas Eve into Christmas morning as the
strong moisture plume associated with today's CA AR attempts to
spill into the northern High Plains. IVT values across the interior
West above the 90th climatological percentile along with the
favorable left-exit region of a quickly traversing 130kt jet streak
will work to squeeze a few tenths of an inch of QPF (at most)
across a region with cold low-level air being reinforced by strong
high pressure to the northeast. WPC day 1.5 probabilities for at=20
least 0.1" of freezing rain are currently 20-50% across north-
central MT. This amount of freezing rain may not be enough for
impacts to infrastructure, but could lead to slippery holiday
travel.



Snell




...Winter Storm/Atmospheric River Key Messages are in effect.=20
Please see current Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-qtGErMs0aLaJ73UGP_o77Cl93lnVgZl3k0GZBYwfbYQ8= qonqKfKWUckd8fr9smCsFtAVUCrx9eG-X6WZR3axB_5YwI$=20



$$

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FOUS11 KWBC 242044
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
344 PM EST Wed Dec 24 2025

Valid 00Z Thu Dec 25 2025 - 00Z Sun Dec 28 2025

*** Continued Heavy Snow on the Sierra Nevada through Friday ***


...Great Lakes to Northeast...
Days 2-3... Maximum impact level from WSSI: Moderate

An impressive plume of Pacific and subtropical moisture ejecting=20
out of the robust longwave trough off the West Coast will traverse the
northern periphery of the ridge axis over the south-central U.S.=20
and head for the Great Lakes Thursday night before reaching the=20
northern Mid-Atlantic/Northeast Friday night. Guidance is in=20
agreement on strong 850-700mb WAA over the north-central U.S.=20
Thursday afternoon with a band of snow developing along the 700mb=20
front. This will result in a combination of snow and some embedded=20 sleet/freezing rain across northern ND and northern MN Thursday=20
night, then across northern WI and the U.P. of MI early Friday=20
morning. The strong but transient 850-700mb WAA will cause a stout=20
warm-nose of >0C temperatures over MI that cause a wintry mix to=20
engulf much of Michigan's Mitten on Friday, with the same icy=20
potential just east of Lakes Erie and Ontario Friday afternoon. The
progressive nature of this disturbance will help to cap snowfall=20
totals to generally <4", with the lone exceptions being the MN=20
Arrowhead and northern half of MI's U.P. where WPC probabilities=20
show moderate chances (40-70%) for snowfall totals >4". Otherwise,=20
ice is of concern across central and southern MI, where WPC=20
probabilities show moderate-to- high chances (50-80%) for ice=20
accumulations of at least one-tenth of an inch in these areas on=20
Friday, including the greater Detroit metro area. There are also up
to 40% chances for a more impactful event with over one-quarter of
an inch.

In wake of a fast moving clipper system over northern New England
on Christmas Day, strong 850mb CAA ahead of a strengthening dome of
Canadian high pressure will result in a cold-air-damming signature
(CAD) that becomes positioned briefly over the Northeast by Friday.
To the west, the same progressive 500mb shortwave trough over the=20
Great Lakes will approach and strong 850-700mb WAA will accompany=20
sufficient 290K isentropic ascent to produce precipitation over the
Northeast and Mid-Atlantic. Healthy mid-to-upper level ascent will
also be supplied in the form of healthy 700mb Q-vector convergence
Friday afternoon and evening. This strong mid-level convergence is
further bolstered by the region being located beneath the diffluent
left-exit region of a 110kt 300mb jet streak. Guidance is keying=20
in on a narrow area of strong 700mb FGEN and vertical velocities=20
directly beneath the 300mb jet streak's left-exit region over=20
northeast PA, the Southern Tier of NY, the Lower Hudson Valley,=20
Poconos and Catskills, and even as far south as the NYC metro area=20
Friday evening. It is here where snow is likely to remain the=20
primary precipitation type with potential for hourly snowfall rates

1"/hr.

Farther south, this classic "over-running" setup with a burgeoning
warm nose of >0C air at low-levels but sub-freezing wet-bulb=20
temperatures at the surface (due to a cold and very dry boundary=20
layer at the onset) will allow for an icy wintry mix of=20
sleet/freezing rain to fall from western PA and northern MD on east
across southern PA and towards the Delaware Valley. Model cross
sections and soundings continue to show a warm nose elevated=20
around 800-750mb, meaning as precipitation falls into a deep cold=20
layer between the surface and 850mb would force sleet to fall across
the northern mid-Atlantic (northern MD, southern/central PA, and=20
into southern/central NJ). This would cut down on snowfall and=20
freezing rain accumulations here, but still could lead to slippery=20
travel conditions Friday night and Saturday morning given some
guidance members show the potential for as much as 2" of sleet in=20
some locations where prolonged periods of sleet occur.

Through 12Z Saturday, WPC and NBM probabilities show moderate=20
chances (50-70%) for snowfall totals >6" in northeast PA, southern=20
NY, northern NJ, western MA, and western CT, and the NYC metro=20
area. Greatest chances for >8" of snowfall (around 30%) are across
the Poconos and Catskills of northeast PA and NY down into northern
NJ. On the flip side, WPC ice probabilities show moderate chances=20
(50-70%) for ice accumulations over a quarter of an inch along the=20
Laurel Highlands and central Appalachians. This amount of ice would
have the potential to produce scattered tree damage and power=20
outages. Light ice accumulations and accumulating sleet is=20
expected through southeast PA, the Balt-Wash metro areas and into
NJ/DE. The Philadelphia metro could see more snow than=20
sleet/freezing rain, but some wintry mix combination can be=20
expected that results in slick travel conditions through Saturday=20
morning. There remains ongoing fluctuations in the forecast track=20
which could result in additional changes in which areas see the=20
most snow and ice. Regardless, WPC's WSSI-P show >50% odds for=20
Minor Impacts across a large region from western PA to as far east=20
as the Tri-State area between 1AM EST Fri - 7AM EST Sat. Residents=20
and travelers following Christmas will want to keep a close eye on=20
this forecast over the next couple of days.


...California/Sierra Nevada...=20
Days 1-3... Maximum impact level from WSSI: Extreme

Extreme snow rates currently on the High Sierra will diminish=20
later this afternoon as the AR plume shifts to eastern Nevada.=20
Snow becomes more showery with more moderately heavy rates and=20
lower snow levels of 6000/7000ft by 00Z in the continued southerly
flow behind the main AR plume. The next moisture plume arrives=20
early Thursday morning with snow levels of 55000/6500ft and heavy=20
snow rates of 2-3"/hr through midday before rates again decrease in
showery conditions through the afternoon. The last larger punch of
moisture arrives Thursday evening with persistent snow levels of=20
5500/6500ft through the night before dropping to 5000ft for Friday
with continued moderately heavy rates (1-2"/hr). Precipitation is=20
expected to finally wane by Friday night as upper-level ridging=20
builds into the eastern Pacific and the meandering upper low over=20
far northern CA weakens into a positively-tilted trough that shifts
east across the Great Basin.

The lower snow levels and rounds of heavy snow through Friday will
lead to increasing travel and infrastructure impacts. Additional
snowfall in excess of 3ft can be expected above 6000ft along the=20
extent of the Sierra Nevada.

Far northern CA ranges (Shasta Siskiyou/Klamath/etc) can expect
moderately heavy snow above 5000ft through tonight with snow levels
dropping to 4000ft on Thursday with the higher rates continuing
through Thursday night before easing through Friday as low=20
pressure lingering near Cape Mendocino finally shifts east. Some=20
snow impacts to I-5 near Mt Shasta are possible mainly early Friday.

Snow levels drop to around 7000ft tonight where they linger through=20
Friday. Impactful snow looks to remain higher than Big Bear Lake.=20

Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below.


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate to Major

The aforementioned strong AR plume shifting east from the Sierra
Nevada this afternoon will continue to shift over the Great Basin=20
and reach the western Rockies by this evening before the intensity
greatly diminishes overnight. Snow levels are high in this=20
moisture shield, 8000-9000ft over the Great Basin and the Rockies=20
through central ID and WY with much lower precip rates and snow=20
levels of 6000-7000ft in northern ID and MT through tonight. Day 1=20
snow probs for >6" are 40-80% in the higher Sawtooths, Wind=20
Rivers, and Uintas, with 30-60% in the Absarokas, western CO
ranges, southern UT ranges, and highest central NV ranges.

The next moisture surge through CA early Thursday brings=20
widespread precip at lower rates than before across the Great Basin
and western and now northern Rockies with lower snow levels around
6000-7000ft Thursday night through Friday. Day 2 snow probs for=20

6" are 40-80% again for the Sawtooths, Wind Rivers, Tetons, and=20

Absarokas with 30-60% for the central NV ranges, Uintas, and
northern ID/western MT ranges.

The upper trough comes ashore over the Pac NW Friday with moderate
precip rates and Cascades snow levels around 2500ft in WA and=20
3500ft in OR. Day 2.5 snow probs for >6" are now 50-90% in the WA=20
Cascades, including Snoqualmie Pass, and 40-70% for the OR=20
Cascades including Santiam Pass. Snow levels also fall across much=20
of the Great Basin and Rockies on Friday, with levels below=20
3000-4000ft in the northern Rockies and 5000-7000ft in the central=20
Great Basin and remaining around 7000ft in the central Rockies.=20
This allows for more widespread moderate snowfall from the ranges=20
of northern/central ID and northwest MT to northern UT and western
WY, where WPC probabilities on day 2.5 for >6" are 50-80% above=20
the aforementioned snow levels.

The inland pushing trough axis will bring decent snows across the
northern and central Rockies Friday night/Saturday.


...Northern Montana...=20
Days 1-2... Maximum impact level from WSSI: Minor

Strong 850-700mb WAA and anomalous Pacific moisture overrunning a=20 sub-freezing boundary layer will provide a setup for freezing rain
tonight and into Christmas morning over northern MT though QPF is a
question. Surface temperatures will remain well below freezing=20
through 12Z Thursday while a burgeoning warm nose of >0C air=20
resides within the 850-750mb layer per CAMs soundings. While some=20
sleet may mix in at times, freezing rain will be the primary=20
concern through Christmas morning. Based on some soundings Thursday
afternoon, however, there is the potential for lingering freezing=20
fog across northeast MT and northwest ND. In fact, some model=20
members suggest prolonged moisture advection and sub-freezing temps
near the MT/ND and Canada border may keep freezing drizzle in the=20
forecast Christmas night and into Friday morning. WPC probabilities
show low chances (<30%) for ice accumulations over one-tenth of an
inch in north- central MT, but most accumulations will be less=20
than one- tenth across the northern tier of "Big Sky Country".=20
Expect potentially hazardous travel conditions across much of=20
north- central and northeast MT tonight and through Christmas=20
morning, as depicted by the Minor Impacts on the WSSI.


Mullinax/Jackson




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!_TGyp3Ju54N-UcQ8HVhlEwuc26EkDO2dwLP3MMwRwDfNA= Wm2qQYg4ms8WStXcEBZSQHu0Z6O9E0XwoiDPybqQ-vgKIQ$=20



$$

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FOUS11 KWBC 250703
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
203 AM EST Thu Dec 25 2025

Valid 12Z Thu Dec 25 2025 - 12Z Sun Dec 28 2025

*** Continued Heavy Snow on the Sierra Nevada through Friday ***


...Great Lakes to Northeast...
Days 1-2... Maximum impact level from WSSI: Moderate

Quasi-zonal flow will direct a plume of moisture originating from=20
the West along the US/Canadian border today/tonight with WAA-driven
snow over the MN Arrowhead into the U.P. of Michigan. With cold=20
sub-32F sfc temps over parts of MN/WI/Lower MI at precip onset=20
tonight, some freezing rain is likely with minor accumulations over
MN/WI. WPC probabilities for at least 4 inches of snow are low to=20
moderate (20-60%) over the far northeastern MN Arrowhead into the=20
Keweenaw Peninsula.=20

Into D2, shortwave will push through northern Lower MI with its=20
sfc reflection over IN/OH and the 850mb low moving through BUF. The
sfc low will weaken as it approaches the Appalachians, getting too
far behind the mid-level shortwave, and ultimately jumping into=20
the Atlantic by 12Z Sat. From Friday to Saturday morning, a variety
of ptypes are expected over the region (central Appalachians/Mid-=20
Atlantic to the Northeast). The stubborn cold surface air will hold
tight over Lower MI and especially into the Laurel Highlands in=20
western PA where significant freezing rain is possible. WPC=20
probabilities of at least 0.10" icing are high (>70%) from around=20
Detroit and into western PA/western MD, with 40-60% probabilities=20
of at least 0.25" icing in these areas as well. Light icing is=20
likely on either side of this zone of maximum probabilities -- on=20
the south side along the I-66 corridor (DC) and into eastern WV. To
the north/northeast, deeper cold air at the surface will allow for
sleet to be a dominant ptype over central/eastern PA with up to an
inch of so possible. To the north, from central NYS through=20
northeast PA into the Catskills/Poconos and to the NYC Metro area,=20
an axis of moderate snow is possible, driven by the stronger height
falls at the nose of the incoming 130kt jet. The whole scenario is
still uncertain in where the transition zones align as some of the
00Z guidance (e.g., the NAM) were much farther northeast with the=20
WAA than the other global guidance. The recent trend has been=20
toward this milder scenario but only nudged the forecast somewhat=20
given the lead time still.=20

WPC probabilities for at least 4 inches of snow are >50% in a zone
bounded between I-890/Rt 17/I-476 to the west, the southern=20
Adirondacks on the north side, Berkshires/I-91 to the east, and=20
into the NYC Metro/Long Island to the south. Though the system will
be progressive, combination of higher SLRs and upslope could yield
more than 8 inches of snow into the southern Catskills.=20


...California/Sierra Nevada...=20
Days 1-3... Maximum impact level from WSSI: Extreme

The next moisture plume with the long-lived atmospheric river=20
event will arrive this morning into CA amid lower snow levels=20
around 55000-6500ft and heavy snow rates of 2-4"/hr through midday=20
before rates again decrease in showery conditions through the=20
afternoon. The last larger punch of moisture arrives this=20
evening/overnight with persistent snow levels of 5500/6500ft=20
through the night before dropping to 5000ft for Friday with=20
continued moderately heavy rates (1-2"/hr). Precipitation is=20
expected to finally wane by Friday night as the upper trough moves=20
ashore with ridging to follow. The lower snow levels and rounds of=20
heavy snow through Friday will lead to increasing travel and=20
infrastructure impacts. Additional snowfall of 2-5ft can be=20
expected above 6000ft along the extent of the Sierra Nevada.

Far northern CA ranges (Shasta Siskiyou/Klamath/etc) can expect=20
moderately heavy snow above 4000ft or so as snow levels dip to=20
start the period. Some snow impacts to I-5 near Mt Shasta are=20
possible mainly early Friday. Most snow will end by 12Z Saturday.=20
Over SoCal, snow levels drop to around 7000ft tonight where they=20
linger through Friday. Impactful snow looks to remain higher than=20
Big Bear Lake.=20

Key Messages for the CA atmospheric river and subsequent low that=20
maintains impacts through Friday are linked below.


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Though the AR affecting CA will infuse some moisture into the=20
Rockies, an incoming trough out of the Gulf of Alaska will drop=20
into the PacNW on Friday with a renewed increase of moisture to the
area as snow levels remain on the lower side -- generally=20
2500-3500ft in the Cascades. That trough will exit WA early=20
Saturday and bring widespread light to moderate snows to the=20
northern Rockies the CA AR (via the separate upper trough) moves=20
inland as well. This will act to expand the area of snow across=20
most of the Great Basin to central Rockies Saturday into early=20
Sunday before the entire full- latitude trough then exits onto the=20
Plains just beyond this forecast period. Snow levels will be much=20
lower over MT/ID and western WY compared to UT/CO (closer to the=20
warmer AR) -- generally 4000ft to the north (and falling to the=20
valley floors) ramping up to around 7000-8000ft over CO, falling to
below 6000ft by early Sunday morning.=20

For days 1-2, WPC probabilities for at least 12 inches are >50%=20
above about 2500ft in the WA Cascades (still affecting the passes),
5000ft in western MT, 6000ft in central ID, 7000-8000ft in the=20
western WY ranges, and about 9000ft in the Uintas. For days 2-3,=20
the focus will be on the CO Rockies where WPC probabilities for at=20
least 8 inches of snow are >50% above about 9000ft.=20


Fracasso


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!9DtysQKcTuXQhxMcKfHeYjCpIeqFJmrWgTAvy3gKqa5WQ= 6_sMtVxVGdijBYGfI2ZZ8pAjxJzPTa_xFdkiKV4mKY6LGw$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!9DtysQKcTuXQhxMcKfHeYjCpIeqFJmrWgTAvy3gKqa5WQ= 6_sMtVxVGdijBYGfI2ZZ8pAjxJzPTa_xFdkiKV4LAyvh_8$=20



$$

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FOUS11 KWBC 251900
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Thu Dec 25 2025

Valid 00Z Fri Dec 26 2025 - 00Z Mon Dec 29 2025

*** Continued Heavy Snow on the Sierra Nevada through Friday ***


...Great Lakes to Northeast...
Days 1-2... Maximum impact level from WSSI: Moderate

Quasi-zonal flow continues to direct a plume of moisture=20
originating from the West along the US/Canadian border=20
leading to WAA- driven snow over the MN Arrowhead into the U.P. of
Michigan. With cold sub-32F sfc temps over parts of MN/WI/Lower MI
at precip onset tonight, some freezing rain is likely with minor=20 accumulations over MN/WI. WPC probabilities for at least 4 inches=20
of snow are low to moderate (20-60%) over the Keweenaw Peninsula
into the eastern U.P.=20

Into D2, shortwave will push through northern Lower MI with its=20
sfc reflection over IN/OH and the 850mb low moving through BUF. The
sfc low will weaken as it approaches the Appalachians, getting too
far behind the mid-level shortwave, and ultimately jumping into=20
the Atlantic by 12Z Sat. From Friday to Saturday morning, a variety
of ptypes are expected over the region (central Appalachians/Mid-=20
Atlantic to the Northeast). The stubborn cold surface air will hold
tight over Lower MI and especially into the Laurel Highlands in=20
western PA where significant freezing rain is possible. WPC=20
probabilities of at least 0.10" icing are high (>70%) from central
to southeast MI, including Detroit, as well as into western=20
PA/western MD. 40 to 70% probabilities of at least 0.25" icing=20
exist over southeast MI down through northwest PA into the Laurel=20
Highlands. Light icing is likely on either side of this zone of=20
maximum probabilities -- on the south side along the I-66 corridor=20
(DC) and into eastern WV. To the north/northeast, deeper cold air=20
at the surface will allow for sleet to be a dominant ptype over=20 central/eastern PA with up to an inch of sleet possible.=20

To the north, from central NYS through northeast PA into the=20 Catskills/Poconos and to the NYC Metro area, an axis of moderate to
locally heavy snow is increasingly likely, driven by the stronger=20
height falls at the nose of the incoming 130kt jet. Beginning to=20
see numerical guidance fall in line on the axis of greatest=20
snowfall potential with the NAM shifting further south compared to=20
its placement at 00z. Rest of the dynamical guidance is keying on=20
the area from southern NY state down through the Lower Hudson to=20
NYC and 50-75 miles on either side seeing at least 4" with >6"
becoming a greater likelihood around the Catskills into the Lower
Hudson Valley to the north of NYC.=20=20

WPC probabilities for at least 4 inches of snow are still >50% in
a zone bounded between I-890/Rt 17/I-476 to the west, the southern
Adirondacks on the north side, Berkshires/I-91 to the east, and=20
into the NYC Metro/Long Island to the south. Probabilities for at
least 6" are now between 50-70% for that area of central NY state
down through southern NY, including the Catskills/Lower Hudson/NYC
corridor south and east of I-88. Though the system will be=20
progressive, combination of higher SLRs and upslope could yield=20
more than 8 inches of snow into the southern Catskills where areal
average maxima is currently positioned with some deterministic
indicating >10" on their outputs.

Fracasso/Kleebauer

...California/Sierra Nevada...=20
Day 1... Maximum impact level from WSSI: Extreme

*** Heavy Snow Continues on the Sierra Nevada through Tonight ***

The final round of widespread heavy snow arrives early this evening=20
to the northern Sierra Nevada then works its way down the length of=20
the Sierra Nevada through the overnight. Expect a few hours of 2-
3"/hr rates (per the 12Z HREF) above the snow level of 5000ft=20
(north/central Sierra) to 6000ft (southern Sierra) with an=20
additional 12-18" overnight.

Moderate snow showers continue into Friday evening with snow levels=20
dropping to 4500ft. The upper trough which had been offshore finally=20
shifts east to the Great Basin Friday night, cutting off Sierra snow=20
by 12Z Saturday.

Far northern CA ranges (Shasta Siskiyou/Klamath/etc) can expect two=20
more rounds of heavy snow: this evening above 4000ft and early=20
Friday down to 3500ft. Snow impacts to I-5 near Mt Shasta are likely=20
Friday. Some moderate snow lingers Friday night before ending by 12Z=20 Saturday.=20

For SoCal, snow levels remain around 7000ft through Friday morning=20
and most of the additional precip. Snow levels do drop below 6000ft=20
Friday afternoon with some 1"/hr rate potential around Big Bear Lake=20
into the evening before tapering off.

Jackson

...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Deep low pressure off CA will continue to infuse moisture across the=20
West with a separate trough pushing down the BC coast Friday and=20
over the northern Rockies Saturday providing a final focus for=20
precipitation and ending the active pattern.=20

Ongoing snow over the Cascades tapers off this evening with moderate=20
to locally heavy snow for the length of the Cascades Friday and=20
Friday night with snow levels dropping on the WA Cascades from=20
3000ft to 1000ft and over the OR Cascades to 2000ft. Day 1.5 snow=20
probs for >8" are 50-90% on the WA/OR Cascades including for the=20
Snoqualmie and Santiam passes.

The next round of moisture from CA arrives into the northern Rockies=20
this evening with prolonged moderate to heavy snow until the cold=20
frontal passage Friday night. Snow levels drop from 6000/7000ft to=20 3000/4000ft through this time leading to increasing travel impacts.=20
Day 1.5 snow probs for >8" are 50-80% over the Sawtooths, northern=20 ID/western MT ranges, western WY ranges, the higher central NV=20
ranges, and the Wasatch.

The progression of the cold front is notable with the Day 2.5 snow=20
probs for >8" limited to the Wasatch and 50-80% for northern and=20
western CO Ranges.

Jackson


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!8i3BFfMTliwgu31BIOZxaNWLw-_P9c1QQwNBoXOUOClXz= ScdxcVlv1YeP0fW3SBOPRYYRBlFr9dsxT95BAZWTMW9e4E$=20



$$

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FOUS11 KWBC 260648
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
148 AM EST Fri Dec 26 2025

Valid 12Z Fri Dec 26 2025 - 12Z Mon Dec 29 2025

*** Continued Heavy Snow on the Sierra Nevada through Friday ***

*** Heavy Wintry Mix tonight through Friday night from the Great
Lakes through the Northeast and Mid-Atlantic ***

...Great Lakes to Northeast...
Days 1 & 3... Maximum impact level from WSSI: Moderate=20

Current UA analysis pin-points our shortwave that be involved in
the next winter focused disturbance over the northern and eastern
CONUS. Forecast is for the shortwave trough to push through=20
northern Lower MI with a sfc reflection developing over IN/OH this
morning. Major player in the forecast evolution will also be the
attendant 850mb low which will migrate over Lower MI, cutting east
to BUF leading to persistent southwesterly flow within the upper
portion of the boundary layer. The sfc low will weaken as it=20
approaches the Appalachians, getting too far behind the mid- level=20 shortwave, and ultimately jumping into the Atlantic by 12Z Sat.=20

=46rom Friday to Saturday morning, a variety of ptypes are expected=20
over the region (central Appalachians/Mid- Atlantic to the=20
Northeast) thanks to the WAA regime progged between 925-800mb. The
stubborn cold surface air will hold tight over Lower MI and=20
especially into the Laurel Highlands in western PA where=20
significant freezing rain is possible. WPC probabilities of at=20
least 0.10" icing are high (>70%) from central to southeast MI,=20
including Detroit, as well as into western PA/western MD. 40 to 70% probabilities of at least 0.25" icing exist over southeast MI down
through northwest PA into the Laurel Highlands. Light icing is=20
likely on either side of this zone of maximum probabilities -- on=20
the south side along the I-66 corridor (DC) and into eastern WV. To
the north/northeast, deeper cold air at the surface will allow for
sleet to be a dominant ptype over central/eastern PA with up to an
inch of sleet possible.=20

To the north, from central NYS through northeast PA into the=20 Catskills/Poconos and to the NYC Metro area, an axis of moderate to
locally heavy snow is likely, driven by the stronger height falls=20
at the nose of the incoming 130-135kt jet. 00z model suite is in
agreement on the axis of heaviest snowfall aligning over the area=20
from Central and Southern NY state down through the Lower Hudson=20
to NYC and 50-75 miles on either side seeing at least 4" with >6"=20
becoming a greater likelihood around the Catskills into the Lower=20
Hudson Valley to the north of NYC.=20

WPC probabilities for at least 4 inches of snow are still >50% in
a zone bounded between I-890/Rt 17/I-476 to the west, the southern
Adirondacks on the north side, Berkshires/I-91 to the east, and=20
into the NYC Metro/Long Island to the south. Probabilities for at
least 6" are now between 50-90% for that area of central NY state=20
down through southern NY, including the Catskills/Lower Hudson/NYC=20
corridor south and east of I-88. Though the system will be=20
progressive, combination of higher SLRs and upslope could yield=20
more than 8 inches of snow into the southern Catskills where areal=20
average maxima is currently positioned and latest WPC probabilities
for >8" now upwards of 40-70%.=20

On D3, another surface cyclone will intensify and move northeast
through the Upper Midwest and Great Lakes. Ensemble means show a
rapid CAA pattern within the northwest side of the cyclone leading
to snowfall breaking out across northeastern MN into northern WI
and the Michigan U.P. Best chance for at least 4" of snow lies over
the western U.P. due to lake effect threat kicking in downwind of
Lake Superior. WPC probabilities for >4" are now between 50-90%
across all of the central and western U.P. with the highest
probabilities across the Iron Range over into the Keweenaw
Peninsula.=20

Kleebauer


...California/Sierra Nevada...=20
Day 1... Maximum impact level from WSSI: Extreme

*** Heavy Snow Continues on the Sierra Nevada through this morning***

Final push of moderate to heavy snowfall forecast across the Sierra
Nevada today with the heaviest likely to occur this morning before
slowly waning as our AR event finally comes to an end. Prior,
expect heavy snow rates between 2-3"/hr at times leading to
additional accumulations between 1-2ft above 9000ft MSL. WPC
probabilities for >12" are still between 50-80% for much of the
northern and central Sierra Nevada with the highest probabilities
co-located with the area near Mammoth up to just south of I-80.
Storm totals will approach 4-6ft or more after the full event is
complete leading to significant impacts to travel even after the
event has completed.=20

Kleebauer


...Pacific Northwest, Great Basin and Rockies...=20
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Deep low pressure off CA will continue to infuse moisture across=20
the West with a separate trough pushing down the BC coast Friday=20
and over the northern Rockies Saturday providing a final focus for=20 precipitation and ending the active pattern.=20

Moderate to locally heavy snow for the length of the Cascades will
occur through today into early Saturday morning with snow levels=20
dropping on the WA Cascades from 3000ft to 1000ft and over the OR=20
Cascades to 2000ft. Snow probs for >8" are 50-90% on the WA/OR=20
Cascades including for the Snoqualmie and Santiam passes.

Moisture from the leading edge of the AR from the Pacific will
continue to maintain a prolonged moderate to heavy snow forecast=20
until the cold frontal passage later this evening. Snow levels=20
drop from 6000/7000ft to 3000/4000ft through this time leading to=20
increasing travel impacts. Snow probs for >8" are 50-90% over the=20
Sawtooths, northern ID/western MT ranges, western WY ranges, the=20
higher central NV ranges, and the Wasatch.

The progression of the cold front is notable with the Day 2 snow=20
probs for >8" limited to the Wasatch and 50-80% for northern and=20
western CO Ranges.

Jackson/Kleebauer


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!5w3TbUg8Y9oJAqQvGcX7aMFVDpRF8TwGKKw-v-VfCNlHR= jP15638ILZXRJ6yNkbDkKwnNrS8Qi7kz_kEq-Rg3Pm5YCc$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!5w3TbUg8Y9oJAqQvGcX7aMFVDpRF8TwGKKw-v-VfCNlHR= jP15638ILZXRJ6yNkbDkKwnNrS8Qi7kz_kEq-Rg9_jxf4A$=20



$$

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FOUS11 KWBC 262108
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
408 PM EST Fri Dec 26 2025

Valid 00Z Sat Dec 27 2025 - 00Z Tue Dec 30 2025

*** Heavy Wintry Mix through tonight for the Northeast ***

*** Major Winter Storm Develops over the Great Lakes Sunday Night,
Spreading through the Northeast Monday ***

...Northeast...=20
Day 1... Maximum impact level from WSSI: Major=20

The variety of ptypes continue tonight for the central=20 Appalachians/Mid-Atlantic with heavy snow bands over eastern NY
through southern New England and the NYC metro. The main note is
the northward shift in the heavy snow a bit north of the NYC metro
that had been in the axis the past. Day 1 snow probs for >8" are
30-50% in the lower Hudson Valley, over western CT, and eastern
Long Island and around 10% in NYC proper. The stubborn cold air
damming will keep freezing rain continuing over the Laurel
Highlands and western MD until precip diminishes overnight.=20


...The West...=20
Days 1-2... Maximum impact level from WSSI: Moderate=20

Potent northern stream trough axis over Vancouver Island this
afternoon will continue to dig south as it tracks east over the
northern Rockies through Saturday night before shifting over the
northern Plains Sunday. Meanwhile the positively-tilted southern=20
stream trough along the northern CA Coast will swing east and cross
the central Rockies Saturday night. Long wave ridging behind this
trough finally brings an end to this active winter pattern.=20

Moderate snow continues for the Cascades and Sierra Nevada tonight.=20
Snow levels drop on the WA Cascades to 1000ft by early evening and
probably 500ft overnight, to 2000ft over the OR Cascades, and
around 4000ft on the Sierra. Day 1 Snow probs for >6" are 50-90%=20
on the WA/OR Cascades including for the Snoqualmie and Santiam=20
passes, and 40-60% for the Sierra Nevada.

Moisture streaming over the Intermountain West ahead of the trough
axis will continue to produce widespread snow over terrain through
Saturday. Day 1 snow probs for >6" are 60-90% over the northeast OR
and ID/western MT ranges where snow levels will drop to 2000ft
tonight and to ground level Saturday before snow tapers off. Those

6" probs are 40-80% for western WY ranges down through UT and

western CO where snow levels drop from 6000-8000ft now to
4000-7000ft overnight and 2000-6000ft Saturday.=20

On Saturday night the cold front associated with the strong trough
will quickly drop through the central High Plains and produce
moderate to heavy snow across the CO Rockies and some banded snow
for the Denver metro and east. Day 2 snow probs for >6" are over
50% for most of the CO ranges, with 30-60% probs for >2" broadly
along and east of the Palmer Divide.


...Great Lakes/Northeast...
Days 2-3... Maximum impact level from WSSI: Major

The potent northern stream trough reaching the northern Plains
Sunday will close off as it digs over Iowa through the day with the
surface low undergoing rapid intensification as it shifts northeast
over Michigan Sunday night into Monday. A rapid CAA pattern within
the northwest side of the cyclone will lead to comma head snowfall
Sunday afternoon over MN/western WI which quickly becomes lake=20
enhanced over northern WI/all of the U.P. Sunday night. Intense
flow behind the very deep system will produce strong lake effect=20
snow in its wake Monday.=20

Day 2.5 snow probs for >12" are 30-60% along the northern U.P.
and WI shorelines with most of that falling in just 12 hours. Those
probs for >12" increase to 50-80% and spread to far northern L.P.
for Day 3 once there's 24 hours worth of the event. Strong wind
will certainly make this event more significant.=20

Warm air advection ahead of this low will result in a wintry mix
over the Northeast with Day 3 0.1" ice probs 40-80% in north-
central PA through southern/eastern NY and central New England.

Key Messages have been initiated for this system.


Jackson



...Winter Storm Key Messages are in effect for the Great Lakes and
the Northeast as linked below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!8iGycxItJwAT0tIRVCrVSluWRyYd9CAQJjq7Y7Pwue0Yw= CKgq_E7UciAIWIwfjsvdiX4ZFHRBj1cVRx1BzK0jI3P0ac$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!8iGycxItJwAT0tIRVCrVSluWRyYd9CAQJjq7Y7Pwue0Yw= CKgq_E7UciAIWIwfjsvdiX4ZFHRBj1cVRx1BzK0LZzA8_U$=20



$$

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FOUS11 KWBC 270723
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
223 AM EST Sat Dec 27 2025

Valid 12Z Sat Dec 27 2025 - 12Z Tue Dec 30 2025

*** Major Winter Storm for the Upper Midwest/Great Lakes Sunday=20
Night then into the Northeast Monday ***

...The West...=20
Day 1... Maximum impact level from WSSI: Moderate=20

A healthy shortwave over the MT Divide this morning will continue=20
to move east-southeastward as a southern stream positively-tilted=20
trough (last gasp of the long-lived Atmospheric River event) moves=20
through the Great Basin into the Four Corners region. Moisture=20
anomalies are highest (>80th percentile) over the CO Rockies into=20
the Sangre de Cristos and snowfall amounts will be highest there,=20
generally above 9000-10,000ft.

On Saturday night the cold front associated with the strong trough
will quickly drop through the central High Plains and produce some
light/banded snow for the Denver metro region into the High=20
Plains. WPC probabilities for at least 8 inches of snow are highest

50%) above 8000ft or so. Lighter snow will affect the I-25=20

corridor from Fort Collins to Colorado Springs, but probabilities=20
for at least 2 inches of snow are generally less than 30%.


...Southeastern New Mexico...
Day 3... Maximum impact level from WSSI: Minor

Cold front racing southward from the CO Rockies will leave behind=20
a sfc-700mb baroclinic zone along the Rio Grande as moisture from=20
the Pacific will still be directed eastward across northern Mexico. Temperatures may be just cold enough even to the valley floors for
snow to accumulate, aided by an onset time overnight. WPC=20
probabilities for at least 2 inches of snow are >10% over most of=20 southeastern NM and across the TX border, and are >50% in the=20
Sacramento Mountains above 5000ft.=20


...Great Lakes/Northeast...
Days 2-3... Maximum impact level from WSSI: Major

The potent northern stream trough exiting Montana will close off=20
as it moves across the northern Plains then digs through Iowa late=20
Sunday. Upper jet will become more amplified overnight and help aid cyclogenesis across northern IL into Lower MI as pressures rapidly
drop through the 990s into the 980s mb after 00Z Monday. Snow=20
associated with the approaching cold front from the west will merge
into the developing comma-head snowfall to the northwest of the=20
sfc low Sunday afternoon along an inverted surface trough and on=20
the edge of the moisture gradient to the southeast (where PW=20
anomalies in the warm sector rise to >99th percentile). Snow will=20
expand and increase in intensity over eastern MN through=20
central/northern WI into the U.P. of Michigan as winds increase=20
from the NW to NE, picking up additional moisture from Lake=20
Superior. The low pressure will continue to deepen as it briefly=20
slows over northern Lower MI very early Monday awaiting the mid-
level low from the west. Shortly thereafter, it should reach peak=20
intensity (mid 970s mb) over Lake Huron or Georgian Bay with=20
continued wrap-around moisture as the WCB wraps up and around the=20
low. Snowfall will maximize over the northern short of the U.P.=20
where WPC probabilities of at least 12 inches of snow are >70%. As=20
the low continues through Ontario to Quebec, CAA will bring lake=20
effect snow to the rest of the Great Lakes into D3. WPC=20
probabilities for at least 6 inches of snow D3 are highest south of
Buffalo in the Chautauqua Ridge, aided by a multi-lake connection.
The bombing out of the system will induce strong winds over much=20
of the region, creating additional hazards due to blowing/drifting=20
snow.

Well ahead of the main surface low, warm air advection will=20
overrun cold <32F surface temperatures in the central Appalachians=20
into the Northeast. With precipitation starting overnight, and snow
on the ground through much of the region already, the WAA aloft=20
will have a tough time reaching the surface. This could result in a
widespread icing event to start for central PA northward into the=20 Adirondacks/eastern NY and much of New England. Without a surface=20
high to the north, temperatures will have an easier time rising due
to the freezing rain process itself, but counteracted by snow-=20
covered ground which could act to keep the surface warm front=20
farther south. It may only be when the cold front (or triple point=20
low) approaches that the surface inversion mixes above freezing,=20
albeit briefly. This may be especially true over central/northern=20
New England as the guidance indicates a triple point low could form
and act to keep northern areas below freezing at the surface. WPC=20 probabilities for at least 0.10" icing are >50% over parts of north
central PA and from the Catskills northward into the Adirondacks=20
and eastward through central New England (along/north of the Mass=20
Pike/495) and into western Maine. Greater than 50% probabilities=20
for at least 0.25" icing exist over the Adirondacks and into=20
central VT/NH. Over far northern Maine, though some icing may creep
that far north, snow will be the dominant ptype and WPC=20
probabilities for at least 4 inches of snow are >50% over the North
Woods.


Fracasso


...Winter Storm Key Messages are in effect. Please see current Key
Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!80PYub2ZplDosmeyJ8tIzedJLPmNrNjDbJu4BrjFSG2B9= NJmNb0Hphsqi7fTPlk7IEZ7VeTsrztbptx_IacGPWZVvCQ$=20



$$

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--- SBBSecho 3.28-Linux
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FOUS11 KWBC 272054
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
354 PM EST Sat Dec 27 2025

Valid 00Z Sun Dec 28 2025 - 00Z Wed Dec 31 2025

*** Major Winter Storm for the Upper Midwest/Great Lakes Sunday=20
Night then into the Northeast Monday ***

...Southern Rockies onto the High Plains...=20
Day 1... Maximum impact level from WSSI: Moderate

Northern stream shortwave trough axis over central MT will close
into a low over ND tonight as a reinforcing shortwave dives
southeast over WY. Remnant Pacific moisture will continue to
maintain moderate snow rates over the CO and northern NM Rockies
tonight with snow levels decreasing to valley floors before snow
tapers off early Sunday. Day 1 PWPF for >6" additional after 00Z=20
are 50-70% for northern and western CO Rockies.


The cold front associated with the strong trough will quickly drop
through the central High Plains tonight where left exit dynamics
from a SWly jet ahead of the trough will aid snow and development=20
for the Denver metro region east into Nebraska late tonight into
Sunday. Day 1 PWPF for >2" are 30-50% for the Palmer Divide and
generally less than 10% for the High Plains, though this phenomena
is rarely picked up well by models.=20


...Southeast New Mexico/Guadalupe Mountains...=20
Days 2/3... Maximum impact level from WSSI: Moderate

Cold front racing southward from the CO Rockies Sunday will leave=20
behind a sfc-700mb baroclinic zone along the Rio Grande as moisture
from the Pacific will still be directed eastward across northern=20
Mexico. Temperatures may be just cold enough even to the valley=20
floors for snow to accumulate, aided by an onset time early Monday
with the threat continuing through Monday night. Topographic
enhancement on the Guadalupe and southern Sacramento Mtns raises
Day 2 PQPF for >4" into the 20-40% range in this terrain.


...Great Lakes/Northeast...
Days 2-3... Maximum impact level from WSSI: Major

The potent northern stream trough exiting Montana this evening=20
will close off over ND tonight and jog southeast to Iowa Sunday as
southern stream elements phase in. This will promote rapid surface=20 cyclogenesis as it tracks from northern IL Sunday afternoon through
Lower MI Sunday night.=20

Snow associated with the approaching cold front from the west will
merge into the developing comma-head snowfall to the northwest of=20
the sfc low over MN/northern WI Sunday afternoon along an inverted
surface trough and on the edge of the moisture gradient to the=20
southeast (where PW anomalies in the warm sector rise to >99th=20
percentile). Snow will expand and increase in intensity over=20
northern WI/U.P. of MI Sunday evening, quickly becoming enhanced by
Lake Superior as cyclonic flow rapidly intensifies. Meanwhile,
east/ahead of the low center will be a wintry mix over the northern
L.P. and eastern U.P. with sleet and freezing rain eventually
giving over to snow early Monday.

The low pressure will continue to deepen as it briefly slows over=20
Lake Huron early Monday as the system becomes vertically stacked=20
and occludes. awaiting the mid- level low from the west. Peak
intensity is then Monday morning with MSLP in the mid 970s over=20
Lake Huron or Georgian Bay with the warm conveyor belt now
completed wrapped up and around the low. Snowfall will maximize=20
over the northern shore of the U.P. where powerful onshore flow=20
pivots as the low passes with 1-2ft likely. Day 1.5 PWPF for >6"=20
are over 20% from northern Iowa across eastern MN and central WI,=20
expanding across the northern and western L.P. for Day 2.

Strong westerlies then scream east Monday promoting turbulent LES
banding off Lake Michigan with single banding threats off Lakes=20
Erie and Ontario coupled with blowing/drifting snow. Day 3 PWPF=20
for >8" are over 50% above Erie, PA through the Chautauqua Ridge=20
and south towns of Buffalo as well as across Syracuse and up=20
through the Tug Hill Plateau.=20

Well ahead of the main surface low, warm air advection will=20
overrun cold <32F surface temperatures from central PA Sunday
afternoon through the Northeast Sunday night. Given snow is on the
ground through much of the region, the WAA aloft will have a tough
time reaching the surface. Day 1.5 PWPF for >0.1" is 40-60% in
central PA across the Catskills and southern New England with Day 2
PWPF for >0.25" 50-70% for the northern Hudson Valley through the
Adirondacks and along the St Lawrence, and across VT/NH into
Maine. It is worth noting that without a surface high to the=20
north, temperatures will have an easier time rising due to the=20
freezing rain process itself, but again counteracted by snow-=20
covered ground which could act to keep the surface warm front=20
farther south. It may only be when the cold front (or triple point=20
low) approaches that the surface inversion mixes above freezing,=20
albeit briefly. This may be especially true over central/northern=20
New England as the guidance indicates a triple point low could form
and act to keep northern areas below freezing at the surface.=20
A snow line looks to set up over far northern NH and northwestern
Maine where Day 3 PWPF for >4" are 40-60%.


Jackson



...Winter Storm Key Messages are in effect for the Great Lakes and
Northeast and linked below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-DKELbdACovotXfhPRFe2xuGWS9RPcu6ogCKXoshfphFi= ETLGYltZgapEL0F8gRS-iECCckrboM33Ho2Tm9UNagCyeI$=20



$$

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FOUS11 KWBC 280724
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
224 AM EST Sun Dec 28 2025

Valid 12Z Sun Dec 28 2025 - 12Z Wed Dec 31 2025

*** Major Winter Storm for the Upper Midwest/Great Lakes tonight=20
then into the Northeast Monday ***


...Southeast New Mexico/Guadalupe Mountains...=20
Day 2... Maximum impact level from WSSI: Moderate

A cold front racing southward from the CO Rockies today will leave
behind a sfc-700mb baroclinic zone along the Rio Grande as=20
moisture from the Pacific will be directed eastward across northern
Mexico. Temperatures may be just cold enough even to the valley=20
floors for snow to accumulate, aided by an onset time early Monday=20
D2 with precipitation continuing through Monday night. Topographic=20 enhancement on the Guadalupe and southern Sacramento Mountains will
result in the highest probabilities for at least 4 inches of snow=20
-- generally 40-60%. To the east, light snow of a couple inches is=20
possible to the TX border where WPC probabilities of at least 2=20
inches are 20-50%.


...Great Lakes/Northeast...
Days 1-3... Maximum impact level from WSSI: Major to locally=20
Extreme

A vigorous closed low along the Montana/North Dakota border this=20
morning will dig southeastward into Iowa this evening as the upper=20
jet punches northeastward into the western Great Lakes. This will=20
set the stage for a rapidly-deepening/bombing cyclone the will move
across Lower Michigan tonight then into Canada on Monday. The=20
storm will have three main facets: synoptic snow via comma-=20 head/lake-enhancement from MN to the U.P. of Michigan, freezing=20
rain to its east (PA/Northeast US) in advance of a surface warm=20
front, and lake- effect snow as the system departs across all Great
Lakes.

Snow associated with the approaching cold front from the west will
merge into the developing comma-head snowfall to the northwest of=20
the sfc low over MN/northern WI this afternoon along an inverted=20
surface trough and on the edge of the moisture gradient to the=20
southeast (where PW anomalies in the warm sector rise to >99th=20
percentile). Snow will expand and increase in intensity over=20
northern WI/U.P. of MI this evening, quickly becoming enhanced by=20
Lake Superior as cyclonic flow rapidly intensifies. Just east/ahead
of the low center will be a wintry mix over the northern L.P. and=20
eastern U.P. of Michigan with sleet and freezing rain eventually=20
giving over to snow early Monday.

The low pressure will continue to deepen and briefly slow over=20
Lake Huron early Monday as the system becomes vertically stacked=20
and occludes (awaiting the mid-level low from the west). Peak=20
intensity should be reached Monday morning (mid 970s mb central=20
pressure) over Lake Huron or Georgian Bay with the warm conveyor=20
belt now completed wrapped up and around the low. Snowfall will=20
maximize over the northern shore of the U.P. where powerful onshore
flow pivots as the low passes. Locally, 1-2ft of snow is likely=20
over much of the U.P. D1-2 probabilities of at least 6 inches of=20
snow are >50% from south central MN eastward across the northern=20
1/2 of WI and the northern 1/4 of Lower Michigan northward across=20
all of the U.P., where probabilities of at least 12 inches are=20

70%. Probabilities for at least 24 inches of snow are >20% over=20

much of the northern and eastern U.P.=20

Well ahead of the main surface low, warm air advection will=20
overrun cold <32F surface temperatures from central PA this=20
afternoon through the Northeast tonight. Given snow is on the=20
ground through much of the region, the WAA aloft will have a tough=20
time reaching the surface, especially in normally sheltered=20
locations. Without a surface high to the north, temperatures will=20
have an easier time rising due to the freezing rain process itself,
but again counteracted by snow-covered ground which could act to=20
keep the surface warm front farther south. However, with such a=20
strong southerly flood of warm air, most guidance does show at=20
least a brief changeover to rain for nearly all of the Northeast=20
except for northern New England. Where the cold air holds on the=20
longest, ice could accumulate enough to be hazardous to trees=20
and/or power lines. WPC probabilities for at least 0.25" icing are=20

50% over the Adirondacks and across much of central VT/NH into=20

southwestern Maine. In addition, probabilities for at least 0.50"=20
icing are 20-50% in these regions. Across northern Maine, the=20
column may be stay entirely below freezing near the Canadian border
as a triple point low may help prevent a southerly wind component.
WPC probabilities for at least 4 inches of snow are >30% over far=20
northern Maine.=20

As the low moves through Ontario into Quebec, strong westerlies=20
will favor lake-effect snow across all Great Lakes, but focused=20
downwind of Lakes Michigan, Erie, and Ontario. Some multi-lake=20
connection and variable wind directions could support long-lived=20
single bands far inland away from the lake shores in concert with=20 breezy/windy conditions (i.e., blowing and drifting snow). In=20
addition, upslope flow into the central Appalachians will favor=20
some snow into the Laurel Highlands southward to eastern WV. WPC=20 probabilities for at least 8 inches of snow are >50% over northeast
Ohio and NW PA into the Chautauqua Ridge and south towns of=20
Buffalo as well as over central NYS around Syracuse northward to=20
Watertown and the Tug Hill Plateau. Some areas could see more than=20
12 inches of snow where bands maintain some residence time (>50%=20
chance).=20


Fracasso/Jackson


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!5e4mWU_BbGp6NVxpLE-fbj3sgOfKqTOUhHgdpw2OEItZd= d9WYVDF8OU5YYt0X2VOgRWMrOplBP1Qn3Te_cD8HaImg7I$=20



$$

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FOUS11 KWBC 281952
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
252 PM EST Sun Dec 28 2025

Valid 00Z Mon Dec 29 2025 - 00Z Thu Jan 01 2026

*** Major Winter Storm for the Upper Midwest/Great Lakes and
Northeast into Monday ***


...Great Lakes/Northeast...
Days 1-3... Maximum impact level from WSSI: Major to locally=20
Extreme

There are no shortage of weather-related hazards for this impending
major winter storm. Below is a break down of these hazards over the
next 1-2 days.

--Snow and Wind--

The deepening upper-level low over the Midwest this afternoon will
work in tandem with a coupling 250mb jet streak structure to=20
support a rapidly deepening surface low that will track from=20
northern Illinois through lower Michigan tonight. Anomalous PWATs=20
ahead of the upper low will wrap around the northern and western=20
flanks of the storm's 700mb low, causing heavy snow to ensue just=20
north of the best 850-700mb FGEN from northern WI on east through=20
the U.P. of MI. In addition, moderate-to-heavy snow breaks out=20
beneath the TROWAL over most of MN and into WI this afternoon and=20
into tonight. WPC's Snowband Probability Tracker shows 1-2"/hr=20
snowfall rates (locally up to 3"/hr possible) in the FGEN banding=20
over northern WI and the MI U.P. this evening and into early Monday
morning. If heavy snow was not concerning enough, high winds will=20
accompany this storm thanks to this storm deepening into the 970s=20
over the Great Lakes Monday morning and strong high pressure over=20
the northern High Plains causing a very tight pressure gradient.=20
Wind gusts up to 50 mph are likely in parts of the Upper Midwest=20
and Upper Great Lakes this evening with gusts topping 60 mph=20
possible along the northern shores of MI's U.P and western shores=20
of MI's Lower Peninsula. The aforementioned TROWAL pivots over the=20
Great Lakes early Monday morning with bursts of heavy snow possible
as far south as Chicagoland and southern MI with lingering bands=20
of lake-effect snow over western MI and the Michigan U.P..=20

WPC probabilities show high chances (>80%) for snowfall totals=20

12" from northwest WI throughout most of MI's U.P.. Given the=20

longevity of the snow in the MI U.P. through Monday evening (thanks
to LES bands) WPC probabilities show moderate to high chances=20
(40-70%) for localized totals topping 24" for much of the central
U.P. and even 30% for >30" and just west of Marquette. Farther=20
west, WPC probabilities show moderate- to- high chances (50-70%)=20
for snowfall totals >6" around the Twin Cities metro area on east=20
into western WI. Snowfall totals are forecast to range between 2-4"
along the ND/SD/MN borders and as far south as northern IA, but=20
those totals paired with high wind gusts will likely bring=20
blizzard conditions this afternoon into tonight. Travel will be=20
dangerous to impossible in northern WI and the MI U.P. through=20
Monday. Expect treacherous travel due to whiteout/blizzard=20
conditions in portions of the Midwest this afternoon and through=20
Monday morning due to heavy snow and whipping wind gusts topping 50
mph.

--Hazardous Ice--

A heavy wintry mix begins the storm for the eastern U.P. and MI's=20
Mitten through this evening before transitioning to heavy snow=20
overnight. The boundary layer across much of the Northeast remains=20
cold enough at the onset; via both cold/dry wet-bulb temperatures=20
courtesy of a departing Canadian high to the north, or event=20
lingering snow pack from Friday night's winter storm, to allow for=20
freezing rain to efficiently accumulate on all surfaces starting=20
this afternoon from northern PA and northern NJ on north to the=20
Catskills and Finger Lakes, then into the the Hudson Valley,=20
Adirondacks and on north into northern New England this evening and
into Monday morning. The heaviest icing is most likely to occur in
the Adirondacks, Green, and White Mountains where despite the=20
strengthening WAA aloft, low- level cold will be harder to scour=20
out as sub-freezing temperatures lay trapped in the valleys of=20
these regions.=20

WPC probabilities show high chances (>70%) for ice accumulations=20

0.25" in these mountain ranges with low chances (10-30%) for=20

localized ice accumulations surpassing 0.5". As much as a tenth of=20
an inch of ice is forecast from northern PA this afternoon through
the Poconos, Catskills, Lower Hudson Valley, the St. Lawrence=20
River Valley, through northern CT and central MA, southern NH, and=20
into much of ME. Roads throughout the interior Northeast will be=20
treacherous with lingering ice likely to impact the Monday morning=20
commute. In areas where ice accumulations top 0.25", wind gusts=20
above 30 mph could cause added stress on trees and power lines,=20
leading to instances of tree damage and power outages for the=20
interior Northeast.=20

--Additional Snowfall Monday night and into mid-week--

As the surface low heads north and east into Quebec Monday=20
afternoon, cyclonic flow and strong CAA in wake of the cold=20
frontal passage will keep LES bands and widespread snow showers in=20
the forecast over the (westerly wind) snow belts downwind of Lakes
Erie and Ontario. Plus, NWrly winds will support upslope snowfall=20
from as far north as the Adirondacks, Tug Hill, and Green mountains
to as far south as the Laurel and Potomac Highlands of southern=20
PA, western MD, and eastern WV into Monday night. It is worth=20
noting there is also evidence on 12Z CAMs, via steep low- level=20
lapse rates along a secondary cold front, that snow squalls could=20
race east across eastern OH, much of PA, and Upstate NY Monday=20
afternoon and evening.=20
This is quickly followed by a clipper system that will traverse=20
the Great Lakes from the northwest on Tuesday/Tuesday night,=20
ushering in a round of light to moderate snow over the Great=20
Lakes. The LES machine picks up again over the MU U.P., the Tip of
MI's Mitten, and downwind of Lakes Erie and Ontario into=20
Wednesday before yet another clipper late Wednesday.


...Southeast New Mexico/Guadalupe Mountains...=20
Day 2... Maximum impact level from WSSI: Moderate

A cold front racing south through the High Plains ushers in strong
low-level CAA amidst ENErly flow tonight. This results in=20
topographic enhancement on the Guadalupe and southern Sacramento=20
Mountains that will play a key role in cooling the boundary layer=20
to support snow into Monday. Meanwhile, there are also sufficient=20
synoptic and mesoscale factors to support heavy snow in the=20
Sacramento and Guadalupe Mountains. Sunday night and into Monday,=20
the region will be positioned beneath the divergent right-entrance=20
region of a 250mb jet streak. Over the Southwest U.S., a positively
tilted 500-200mb trough axis stretches as far south and west as=20
the tropical East Pacific. Guidance is in agreement on a healthy=20
plume of anomalous 700-300mb moisture that leads to PWATs that top=20
0.6", or above the 97.5 climatological percentile per ECMWF=20
guidance. Lastly, the 700mb WAA via SWrly flow over southern NM and
west TX runs into northerly 700mb winds over High Plains that=20
causes a band of 700mb FGEN aloft.=20

HREF guidance is highlighting potentially 1"/hr snowfall rates=20
over the Sacramento and Guadalupe mountains between 09Z and 22Z=20
Monday. Given how warm it has been of late in the Southwest, it=20
will take some hours of moderate-to-heavy snow to cool most=20
surfaces to the point where accumulation can steadily occur. WPC=20 probabilities continue to highlight moderate chances (40-60%) for=20
snowfall totals >4" in these mountain ranges. Localized snowfall=20
totals topping 8" are possible in the highest elevations. To the=20
east, light snow of a couple inches is possible to the TX border=20
where WPC probabilities of at least 2 inches are 20-50%. Notable US
roadways that could witness delays due to measurable snowfall are=20
US-285 between Roswell and Carlsbad, then south and west along=20
US-62/180 that cuts through Guadalupe Mountains N.P..

Mullinax/Jackson



...Winter Storm Key Messages are in effect and linked below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!9MbOzC_a4h8PlEg3Du-zJYl39W383D_Up6CEN5HWcYE91= uHIINNvX7liReZmhZKY3mnUrd_ExGkIMLXAceRvVZcd_CY$=20



$$

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FOUS11 KWBC 290718
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
218 AM EST Mon Dec 29 2025

Valid 12Z Mon Dec 29 2025 - 12Z Thu Jan 01 2026

*** Major Winter Storm for the Upper Midwest/Great Lakes and=20
Northeast Transitions to Lake-Effect Snow Today ***

...Great Lakes/Northeast...
Days 1-3... Maximum impact level from WSSI: Major to locally=20
Extreme

Mature cyclone with a central pressure in the mid 970s mb this=20
morning will be near peak intensity, with direct affects lessening=20
through the day. Comma-head/TROWAL snows over Michigan will=20
transition to lake-effect snow by this afternoon as the parent low=20
continues through Ontario into Quebec. In its wake, winds will=20
still be strong, creating blowing and drifting snow even where none
may be falling. Blizzard warnings remain in effect over parts of=20
the Upper Midwest this morning and will continue over the U.P. of=20
Michigan through the day. An additional 8 inches of snow after 12Z=20
is likely (>50% probability) over at least the eastern half of the=20
U.P. With cyclonic flow around the low continuing today, the lake=20
effect machine will kick in downwind of Lake Michigan (this=20
morning) and Erie/Ontario later this afternoon/evening. An=20
additional shortwave will fly in from Canada through the Great=20
Lakes TUesday afternoon into Wednesday, adding a little more lift=20
to the region. Westerly to WNW flow into the central Appalachians=20
will also promote modest snows for eastern WV, western MD, and into
the Laurel Highlands. With the strong flow over the lakes, some=20
multi-lake connection could support long-lived streamers well=20
inland. Yet another shortwave out of Canada later Wednesday into=20
Thursday will help maintain the lake effect off Erie/Ontario=20
through the end of this forecast period.=20

Three-day total snowfall will be highest in NW PA and in the=20
Chautauqua Ridge as well as into central NY near Syracuse and into=20
the Tug Hill Plateau. Winds will sometimes be transient and=20
sometimes rather stationary, and totals may vary widely on a given=20
day. WPC probabilities for at least 8 inches of snow through 12Z=20
Thursday are >50% over western Lower Michigan, northeastern OH into southwestern NY, over the central Appalachians, and into central=20
NY to the Tug Hill. Within these regions, WPC probabilities for at=20
least 18 inches of snow are >50% over NW PA and SW NY and near=20
Syracuse toward Watertown (Oswego, Pulaski, etc.).=20

In the Northeast, the advancing warm front then cold front will=20
flush out the entrapped cold surface air which has resulted in=20
significant freezing rain accumulations so far. A little more icing
of a tenth or so is possible just after 12Z before a quick=20
changeover to rain then back to snow post-FROPA.=20

...Southeast New Mexico/Guadalupe Mountains...=20
Day 1... Maximum impact level from WSSI: Moderate

A cold front plunging southward has brought in much colder=20
temperatures to the region. ENE sfc flow behind it beneath moisture
advecting eastward from the Pacific will lead to snow over the=20
Guadalupe and southern Sacramento Mountains Monday. With 700mb WAA=20
via SWrly flow over southern NM and west TX colliding with=20
northerly 700mb winds over the High Plains, mid-level FGEN could=20
support some modest snow especially over the terrain. WPC=20
probabilities of at least 4 inches of snow are >50% in the=20
mountains, with lighter accumulations eastward to the TX border.=20

...Sierra Nevada...
Day 3...

Incoming moisture from the Pacific will reach the central and=20
southern Sierra Wednesday into Thursday morning. Snow levels are=20
quite high -- 9000 to 10,000ft -- and accumulations will be light=20
even at the highest elevations.=20


Fracasso


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!7Ru7Q96TCj8qd5WETidu4uMWmyltI4zdSiC06mSsEglqs= oUYNTupVvcnufQnOpwIE3y-JgX4oDDayk3ENxa4B5yT3NI$=20


$$

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FOUS11 KWBC 291843
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
143 PM EST Mon Dec 29 2025

Valid 00Z Tue Dec 30 2025 - 00Z Fri Jan 02 2026

*** Major Winter Storm for the Great Lakes and Northeast=20
Transitioning to Lake-Effect Snow Today ***

...Great Lakes/Northeast...
Days 1-3... Maximum impact level from WSSI: Major to locally=20
Extreme

The powerful cyclone responsible for today's heavy snow and
blizzard conditions over the Great Lakes and significant icing in
northern New England will become trapped beneath a strongly -AO/-NAO
regime that keeps prolonged cyclonic-flow over the Great Lakes and
Northeast to close out 2025 and open 2026. Strong WAA over=20
northern New England combined with a sub-freezing boundary layer=20
will keep ice in the forecast a bit longer over the White Mountains
and much of ME. By tonight, brisk W-NWrly over the Great Lakes=20
along with some lingering low-level CAA will keep single-band LES=20
streamers going tonight and through Tuesday downwind of Lakes Erie=20
and Ontario. From the Michigan U.P. on south through the western=20
and northern sections of Michigan's Mitten, numerous LES showers=20
will lead to additional minor-to-moderate snowfall totals with=20
gusty winds causing reduced visibilities in affected areas.

By Tuesday night, a weak trough passing over the Great Lakes will
produce some minor snowfall from WI on east through MI's Lower
Peninsula and over northern IL/IN/OH. This trough will shift
low-level winds over the eastern Great Lakes from NWrly Tuesday
evening, to westerly overnight Tuesday, then WSWrly by Wednesday
morning. This wind shift is in response to a potent 500mb shortwave
over Ontario that will race southeast over Lake Ontario by New
Year's Eve night. This upper trough will not only act as to
reinvigorate the LES machine downwind of Lakes Erie and Ontario,
but it will also be associated with the leading edge of a potent
Arctic front. Incoming CAMs and deterministic guidance is showing
exceptional jet dynamics aloft when combined with relatively steep
low-levle lapse rates to support snow squalls New Year's Eve
afternoon and evening. Both the NAM and GFS snow squall parameters
are showing squall potential from MI's Lower Peninsula on south and
east through eastern OH, western and central PA, and into Upstate=20
NY. The NAM doesn't rule out these snow squalls potentially=20
reaching the I-95 corridor early New Year's Day. This is naturally=20
very poor timing for residents on the roads given the rapid=20
reductions in visibilities and potential accumulations on roads.=20
Those heading out on the roads New Year's Even Night and New Year's
morning should keep a close eye on the forecast in the coming=20
days.=20

In addition to snow squalls, strong upslope ascent into the central Appalachians is likely to cause heavy snow New Year's Night and
into early New Year's Day morning. Lingering cyclonic flow will
keep LES showers in the forecast across the typical snow belt
locations of the Great Lakes through New Year's Day. Through the
afternoon of January 1, WPC's 72-hour snowfall probabilities show
high chances (>70%) for snowfall totals >18" along the Chautauqua
Ridge in northwest PA and western N, including towns just south of
Buffalo. Localized amounts topping 30" somewhere along the Ridge=20
in western NY are possible, as evident by WPC's probabilities for=20

30" totals generally between 10-30%. Just east of Lake Ontario,=20

WPC probabilities show moderate-to-high chances (50-70%) for=20
snowfall totals >18" with Oswego County, NY the most likely=20
epicenter. Note the WSSI does show Major Impact potential for the
Syracuse metro area Tuesday and into Tuesday night. Even far=20
northwest OH sports moderate chances (40-60%) for snowfall totals=20

12". Farther south, the central Appalachians that consist of the=20

Potomac and Laurel Highlands have high chances (>70%) for 3-day=20
snowfall totals topping 8" through the afternoon of January 1,=20
2026. Otherwise, most snowfall across northern MI and the eastern=20
MI U.P. are likely to range between 4-8" and more of a 2-6" range=20
over western MI and northern IN.


...Southeast New Mexico/Guadalupe Mountains...=20
Day 1... Maximum impact level from WSSI: Moderate

The ENErly upslope flow coupled with 700mb WAA/FGEN via SWrly flow
over southern NM and west TX will keep periods of snow ongoing in=20
parts of the Sacramento and Guadalupe Mountains for a little=20
longer today before tapering off this evening. A couple more inches
of snow are forecast and the WSSI continues to depict Minor to=20
locally Moderate Impacts this afternoon in southeast NM and west TX
north of I-20.


...Sierra Nevada...=20
Day 3... Maximum impact level from WSSI: Minor

An unusually deep upper-tough in the tropical East Pacific will
direct a slug of anomalous moisture (above the 99.5 climatological
percentile per ECMWF) at CA on Wednesday and continue into
Thursday. Southerly flow would foster upslope enhancement into the
peaks of the Transverse Ranges and the Sierra Nevada in this case.
However, the lack of a continental polar air-mass over the West
will make any snowfall likely confined to the >9,000ft remote peaks
of the Sierra Nevada. Even despite the healthy slug of moisture,
low SLRs will also make for a heavy/wet snow that will be less
efficient to accumulate in boundary layer conditions so mild. WPC
probabilities show...

Mullinax



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!5qU-SWL0FMuQl4dvXgDp3enNHlEFr08VyNW76WrZTAq5d= rxMbZCok3Roua7BXu_kSntlo4JSilNmu64NtaWIuNxNq0E$=20



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FOUS11 KWBC 300711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Tue Dec 30 2025

Valid 12Z Tue Dec 30 2025 - 12Z Fri Jan 02 2026


...Great Lakes, Central Appalachians, Interior Northeast...
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Deep upper troughing will linger over southern Hudson Bay/James
Bay for the next few days, maintaining broad cyclonic flow out of
central Canada and across the Great Lakes. This will result in a
mostly continuous period of lake effect snow downwind of all Great
Lakes but focused especially east of Lakes Erie and Ontario. Two
mid-level shortwaves will zip through the southwest/southern base
of the trough which will act to disrupt the banding and also infuse
a bit more lift and moisture to the region. With lake temperatures
in the 30s to 40s and 850mb temperatures -15 to -20C, sufficient
lift will be generated over the lakes on a general NW to W flow
from the Upper Lakes to Lower Lakes, respectively. This will set up multi-banded snows over Michigan with multi to strong single
banded snows over NW PA, western NY, and between Syracuse and
Watertown. The bands will modulate due to the shortwaves moving
through the region, with the first tonight and the second Wednesday
with perhaps a third weaken one overnight Thursday. The passage of
the second shortwave and associated surface arctic front may also
bring the threat for snow squalls tomorrow afternoon into the
overnight (New Year's Eve) from Michigan to Ohio to Pennsylvania
per the Snow Squall Parameter.

In addition to the lake effect snows, strong upslope ascent into
the central Appalachians will favor at least modest totals over
eastern WV northward through western MD and into the Laurel
Highlands in PA, especially Wednesday into Thursday.

WPC's 72-hour snowfall probabilities show high chances (>70%) for
snowfall totals >18" in NW PA and along the Chautauqua Ridge in
southwestern NY into some of the Buffalo Southtowns. Localized
amounts could exceed 2-3ft. Just east of Lake Ontario, WPC
probabilities show moderate-to-high chances (50-70%) for snowfall
totals >18" in the region between Syracuse, Watertown, and east of
Rochester (centered around Oswego). Over Michigan, totals will
likely be lower, but still appreciable. WPC probabilities for at
least 8 inches of snow are highest (>50%) near/southwest of the
Keweenaw Peninsula, the eastern U.P., and over northwestern Lower
Michigan. Farther south, WPC probabilities for at least 8 inches of
snow are highest over eastern WV northward to the Laurel Highlands
in PA. Light to perhaps modest snow is also possible into the
Green Mountains in VT via upslope flow.


...Sierra Nevada to the Central Rockies...
Days 2-3... Maximum impact level from WSSI: Minor to Moderate

A deep trough in the subtropical Eastern Pacific will lift toward
California and weaken on Wednesday, spreading generally light to
moderate QPF over the region. Snow levels will be high

9000-10,000ft) where more than 8 inches is likely above 10,000ft

through Thursday night. Lighter precipitation will spread
northwestward through Utah to the CO Rockies amid high snow levels (8000-9000ft) and generally near to under 6 inches of snow.


Fracasso


$$

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FOUS11 KWBC 302044
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
344 PM EST Tue Dec 30 2025

Valid 00Z Wed Dec 31 2025 - 00Z Sat Jan 03 2026


*** New Year's Eve Snow Squall Threat From Michigan through
Interior Northeast ***

...Great Lakes, Central Appalachians, Interior Northeast...=20
Days 1-3... Maximum impact level from WSSI: Major

A deep cold core low will track north NNW from Quebec to the Hudson
Bay through Wednesday night as a series of reinforcing troughs and
impulses tracks below over the Great Lakes and Northeast. This=20
will maintains bouts of LES off all the Great Lakes, but especially
east of Lakes Erie and Ontario through Friday. The most pronounced
swings through the Upper Great Lakes Wednesday and across NY/PA=20
through Wednesday (New Year' Eve) night. 12Z CAMs are in excellent=20
agreement on this arctic front bringing a notable snow squall=20
threat across eastern Michigan Wednesday afternoon and the eastern=20
Great Lakes/PA/NY Wednesday night. The most impactful snow squalls=20
seem to be when above freezing conditions flash freeze behind the=20
cold front. In this case, the cold conditions get colder, so the=20
threat is perhaps more about visibility on roads the night with the
most revelry of the year. Please take caution NYE night in the=20
Interior Northeast. Key Messages are initiated highlighting this=20
NYE snow squall threat (see link at bottom).=20

In addition to the lake effect snows and the snow squalls, strong=20
upslope flow behind the arctic cold front and ahead of the=20
reinforcing trough axis over the central Appalachians will favor a
few hours of heavy snow Wednesday night over central WV northward=20
through western MD and into the Laurel Highlands in PA. Day 1.5
PWPF for >6" are 40-80% over this terrain.

WPC's 72-hour snowfall probabilities remain high (>70%) for=20
additional snow >18" in NW PA through the Chautauqua Ridge in=20
southwestern NY into the Buffalo Southtowns. Localized amounts=20
could exceed 2ft. Just southeast of Lake Ontario, WPC=20
probabilities are now high chances (60-80%) for additional snow=20

18" in the region between Syracuse, Watertown, and east of=20

Rochester (centered around Oswego).=20
Over Michigan, totals will still be appreciable. WPC 72hr=20
probabilities for >12" over 40% in the eastern U.P. and around 25%
in northwestern Lower Michigan.=20


...Down East Maine...
Day 2... Maximum impact level from WSSI: Moderate

The pronounced mid-level trough axis causing snow squalls over the
Interior Northeast New Years night promotes surface low=20
development southeast of Nantucket Thursday morning. An 850mb low=20
tracks over Nova Scotia Thursday afternoon which should grow the=20
precip shield enough to send heavy snow bands into far Down East=20
Maine through the day Thursday. Rates of 1"/hr are likely in these=20
bands with a greater than 50% potential for >6" in southeastern=20
sections of Washington County on Day 2 per the 18Z PWPF.


...High Sierra Nevada to the Central Rockies...=20
Days 2-3... Maximum impact level from WSSI: Minor

A deep trough in the subtropical Eastern Pacific will trend weaker
as it tracks through southern CA early Thursday and over the=20
southern Sierra Nevada through Thursday afternoon. Ongoing precip
ahead of this wave will continue on the Sierra Nevada, but with
snow levels of 10,000ft. The height falls on Thursday bring the
snow levels over the Sierra Nevada down to 8500ft where there are
Day 2 PWPF of 40-70% for >6".=20

Precip also spreads over the Four Corners on Thursday with Thursday
night snow levels around 8500ft in UT/CO where Day 2.5 PWPF for >6"
are 40-60% and around 80% for the highest peaks in the Park Range
of CO.


...Columbia Basin and Gorge...
Days 2-3...

Light precip spreads over the Northwest Thursday and continues into
the weekend. Sufficient cold air in place should make for some
localize icing. Day 2/3 probabilities for >0.1" ice are in the=20
western Columbia Basin into the Columbia Gorge.


Jackson



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!_vlyZufnYh1BMRzABzoFLfdiqeltTFi_akSGZJ-n_rQZY= iucHV_H5wU0zY8ZM8FsO-3d6xFWZZNDagwrftq8QL09nMU$=20



$$

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FOUS11 KWBC 310710
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
210 AM EST Wed Dec 31 2025

Valid 12Z Wed Dec 31 2025 - 12Z Sat Jan 03 2026


*** New Year's Eve Snow Squall Threat From Michigan through=20
Interior Northeast ***

...Great Lakes, Central Appalachians, Interior Northeast...=20
Days 1-3... Maximum impact level from WSSI: Major

A deep cold core low will meander near Hudson Bay through the rest
of the week as a series of reinforcing troughs and impulses track=20
on its southwest/southerly periphery over the Great Lakes and into=20
the Northeast. This will maintains bouts of lake-effect snow off=20
all the Great Lakes, but especially east of Lakes Erie and Ontario.
A rather robust upper through will move out of the Upper Great=20
Lakes this morning and across NY/PA tonight. CAMs show this arctic=20
front bringing a notable snow squall threat across eastern Michigan
this afternoon and the eastern Great Lakes/PA/NY tonight. Though=20
the most impactful snow squalls can be when unfrozen roads get=20
quickly covered with snow and temperatures plunge below freezing=20
(flash freeze behind the cold front), the region is currently cold=20 (10s/20s). Given it is New Year's Eve and the HREF shows the=20
highest probability of >1"/hr rates late this afternoon and=20
evening, the threat to drivers is more acute. Please take caution=20
tonight in the Interior Northeast/Mid-Atlantic. Key Messages are=20 highlighting this NYE snow squall threat (see link at bottom).=20

In addition to the lake effect snows and the snow squalls, strong=20
upslope flow behind the arctic cold front and ahead of the=20
reinforcing trough axis over the central Appalachians will favor a=20
few hours of heavy snow tonight over central WV northward through=20
western MD and into the Laurel Highlands in PA. WPC probabilities=20
for at least 6 inches of snow days 1-1.5 are 40-80% over this=20
terrain.

WPC's 72-hour snowfall probabilities remain high (>70%) for=20
additional snow >18" in NW PA through the Chautauqua Ridge in=20
southwestern NY into the Buffalo Southtowns. Localized amounts=20
could exceed 2ft. Just southeast of Lake Ontario, WPC probabilities
are high chances (>70%) for an additional 18" or more in the=20
region between Syracuse, Watertown, and east of Rochester (centered
around Oswego). Over Michigan, snowfall will trend farther north=20
each day, but totals will still be appreciable in the eastern U.P.=20
where WPC 72hr probabilities for >8" are 40-90% in the eastern U.P.
and around 30-60% in northwestern Lower Michigan.


...Down East Maine...
Day 1-2... Maximum impact level from WSSI: Minor to Moderate

The vigorous mid-level trough moving through the Great Lakes today
will reach New England just after midnight with a surface low over
northern NY into VT. By tomorrow morning, the system will continue
to deepen into the Gulf of Maine, spurring a sub-1000mb low that=20
could quickly deepen to below 990mb as it nears the Bay of Fundy=20
later in the afternoon. This could focus heavier bands of snow=20
right along the coast with >1"/hr rates (~50% probability per the=20
00Z HREF). The system will be quick-moving but could still yield=20
several inches of snow within a 12-hr window. WPC probabilities for
at least 6 inches of snow are >50% near and east of I-95 from the=20
Midcoast northeastward.


...High Sierra Nevada to the Central Rockies...=20
Days 2-3... Maximum impact level from WSSI: Minor

A deep trough in the subtropical Eastern Pacific will lift=20
northward then northeastward into NorCal tomorrow, bringing an=20
expanse of light to moderate precipitation to the Southwest to the=20
Interior West. High snow levels 9000-10,000ft will limit impacts=20
today. For tomorrow, as the trough moves inland, snow levels of=20
will fall to around 8500ft as precipitation gradually ends by late=20
Thursday into early Friday. Moisture will stream ENE across the=20
Great Basin to the CO Rockies where WPC probabilities of at least 8
inches of snow are >50% above 9000ft or so in the Park Range and=20
also into the Tetons in WY.

After a short break, another wave of precipitation will enter the=20
NorCal ranges and northern Sierra with lower snow levels region-=20
wide
-- generally around 6500ft to the north and around 7000ft in
thenorthern Sierra. WPC probabilities for at least 8 inches of
snow through the period are >50% above about 9000ft.=20


...Columbia Basin and Gorge...
Days 2-3... Maximum impact level from WSSI: Minor

Light precip spreads over the Northwest Thursday and continues=20
into the weekend. Sufficient cold air in place could make for some=20
localize light icing. WPC probabilities for >0.10" ice are low=20
(<20%) in the western Columbia Basin into the Columbia Gorge.


Fracasso=20


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!7slxo0TbURtNNxqpRzx7SNwzJQFQzyrcXir7_6NmkW16g= pdOM_ajE5Fi2w8YZ3piSjFtZSa2V3LKJ5cqLNJPXP-nFg0$=20



$$

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FOUS11 KWBC 310712
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
212 AM EST Wed Dec 31 2025

Valid 12Z Wed Dec 31 2025 - 12Z Sat Jan 03 2026


*** New Year's Eve Snow Squall Threat From Michigan through=20
Interior Northeast ***

...Great Lakes, Central Appalachians, Interior Northeast...=20
Days 1-3... Maximum impact level from WSSI: Major

A deep cold core low will meander near Hudson Bay through the rest
of the week as a series of reinforcing troughs and impulses track=20
on its southwest/southerly periphery over the Great Lakes and into=20
the Northeast. This will maintains bouts of lake-effect snow off=20
all the Great Lakes, but especially east of Lakes Erie and Ontario.
A rather robust upper through will move out of the Upper Great=20
Lakes this morning and across NY/PA tonight. CAMs show this arctic=20
front bringing a notable snow squall threat across eastern Michigan
this afternoon and the eastern Great Lakes/PA/NY tonight. Though=20
the most impactful snow squalls can be when unfrozen roads get=20
quickly covered with snow and temperatures plunge below freezing=20
(flash freeze behind the cold front), the region is currently cold=20 (10s/20s). Given it is New Year's Eve and the HREF shows the=20
highest probability of >1"/hr rates late this afternoon and=20
evening, the threat to drivers is more acute. Please take caution=20
tonight in the Interior Northeast/Mid-Atlantic. Key Messages are=20 highlighting this NYE snow squall threat (see link at bottom).=20

In addition to the lake effect snows and the snow squalls, strong=20
upslope flow behind the arctic cold front and ahead of the=20
reinforcing trough axis over the central Appalachians will favor a=20
few hours of heavy snow tonight over central WV northward through=20
western MD and into the Laurel Highlands in PA. WPC probabilities=20
for at least 6 inches of snow days 1-1.5 are 40-80% over this=20
terrain.

WPC's 72-hour snowfall probabilities remain high (>70%) for=20
additional snow >18" in NW PA through the Chautauqua Ridge in=20
southwestern NY into the Buffalo Southtowns. Localized amounts=20
could exceed 2ft. Just southeast of Lake Ontario, WPC probabilities
are high chances (>70%) for an additional 18" or more in the=20
region between Syracuse, Watertown, and east of Rochester (centered
around Oswego). Over Michigan, snowfall will trend farther north=20
each day, but totals will still be appreciable in the eastern U.P.=20
where WPC 72hr probabilities for >8" are 40-90% in the eastern U.P.
and around 30-60% in northwestern Lower Michigan.


...Down East Maine...
Day 1-2... Maximum impact level from WSSI: Minor to Moderate

The vigorous mid-level trough moving through the Great Lakes today
will reach New England just after midnight with a surface low over
northern NY into VT. By tomorrow morning, the system will continue
to deepen into the Gulf of Maine, spurring a sub-1000mb low that=20
could quickly deepen to below 990mb as it nears the Bay of Fundy=20
later in the afternoon. This could focus heavier bands of snow=20
right along the coast with >1"/hr rates (~50% probability per the=20
00Z HREF). The system will be quick-moving but could still yield=20
several inches of snow within a 12-hr window. WPC probabilities for
at least 6 inches of snow are >50% near and east of I-95 from the=20
Midcoast northeastward.


...High Sierra Nevada to the Central Rockies...=20
Days 2-3... Maximum impact level from WSSI: Minor

A deep trough in the subtropical Eastern Pacific will lift=20
northward then northeastward into NorCal tomorrow, bringing an=20
expanse of light to moderate precipitation to the Southwest to the=20
Interior West. High snow levels 9000-10,000ft will limit impacts=20
today. For tomorrow, as the trough moves inland, snow levels of=20
will fall to around 8500ft as precipitation gradually ends by late=20
Thursday into early Friday. Moisture will stream ENE across the=20
Great Basin to the CO Rockies where WPC probabilities of at least 8
inches of snow are >50% above 9000ft or so in the Park Range and=20
also into the Tetons in WY.

After a short break, another wave of precipitation will enter the=20
NorCal ranges and northern Sierra with lower snow levels region-=20
wide -- generally around 6500ft to the north and around 7000ft in=20
the northern Sierra. WPC probabilities for at least 8 inches of=20
snow through the period are >50% above about 9000ft.=20


...Columbia Basin and Gorge...
Days 2-3... Maximum impact level from WSSI: Minor

Light precip spreads over the Northwest Thursday and continues=20
into the weekend. Sufficient cold air in place could make for some=20
localize light icing. WPC probabilities for >0.10" ice are low=20
(<20%) in the western Columbia Basin into the Columbia Gorge.


Fracasso=20



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-B8Gd5J3CMHvmgwLB2jZswa-oCy6ibiKCvgu2UGA8lHj5= LL7w1uqdiqDOaccQM7fRPu1w21VmSPQ1_ojNF0AYgSWa-g$=20



$$

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FOUS11 KWBC 312008
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
308 PM EST Wed Dec 31 2025

Valid 00Z Thu Jan 01 2026 - 00Z Sun Jan 04 2026


*** New Year's Eve Snow Squall Threat For the Lower Great Lakes,
Ohio Valley, through the Interior Northeast ***

...Great Lakes, Central Appalachians, Interior Northeast...=20
Days 1-2... Maximum impact level from WSSI: Moderate

A deep cold core low will meander near Hudson Bay through Friday.
The most notable reinforcing trough of this time crosses northern
MI this evening and the Interior Northeast overnight before
swinging through northern New England through Thursday. The Arctic
front tonight brings a notable snow squall threat at a bit slower
timing than previous forecasts. 12Z CAMs note the eastern Midwest
and eastern Great Lakes should get the front in the mid-evening
hours with the Upper Ohio Valley, PA, and southern NY overnight
with some semblance crossing NYC prior to sunrise Thursday/New
Years Day. The frontal crossing of Lake Erie in particular this
evening looks to enhance ongoing LES from westerly flow into areas
just south of Buffalo. The 12Z HREF highlights a risk period for
2"/hr snow from 22Z to 03Z south of Buffalo through the Chautauqua
Ridge before tapering off for a few hours as the fetch turns NWly
behind the front.

Though the most impactful snow squalls can be when=20
unfrozen roads get quickly covered with snow and temperatures=20
plunge below freezing (flash freeze behind the cold front), the=20
region is currently cold (10s/20s) and the front will make it
colder. Given it is New Year's Eve the the timing for much of
western NY/PA and eastern Ohio is around midnight, please take=20
caution tonight on the roads. Key Messages have been updated. (see
link at bottom).

Continued westerly upslope flow ahead of the arctic cold front will
retain upslope snow showers on the central Appalachians with rates
increasing right up until the cold frontal passage early Thursday.
The 12Z HREF indicates likely >1"/hr snow rates working their way
down the Laurel Highlands in PA, western MD, and central WV from=20
02Z to 12Z where Day 1 WPC probabilities for >6" snow are 40-90%.=20

Flow becomes WNWly again late Thursday with LES off Erie and in
particular Lake Ontario then through Friday. 48hr probs for >12"
additional Days 1/2 are 50-80% southeast of both lakes with the
greatest risk generally just north of Syracuse.


...Eastern Maine...=20
Day 1... Maximum impact level from WSSI: Moderate

The vigorous mid-level trough moving through the Great Lakes this
evening will reach New England late tonight with a more pronounced
surface low tracking over the Gulf of Maine Thursday. This shifts
the heavy snow focus farther inland with a heavy snow forecast
now from the central Maine coast up through eastern Maine. The 12Z
HREF provides an excellent picture of the threat with >1"/hr rates
moving onto the central coast around 14Z and rotating through
eastern Maine through 22Z. Day 1 PWPF for >6" is now 50-80% from
Penobscot Bay east along the coast and north through areas east of
I-95.=20


...High Sierra Nevada through the Central Rockies...=20
Days 1-3... Maximum impact level from WSSI: Minor

A deep trough in the subtropical Eastern Pacific will lift=20
NNE through the central CA coast early Thursday before crossing the
Sierra Nevada and into Nevada Thursday evening, reaching CO Friday
morning. High snow levels of 9000-10,000ft ahead of the low will=20
limit impacts into Thursday morning. However, as the trough moves=20
inland, snow levels on the Sierra Nevada will fall to around=20
7500ft Thursday afternoon, bringing heavy snow until precipitation=20
ends that evening. The 12Z HREF highlights 16Z to 22Z Thursday as a
period of >1" snow rates on the southern Sierra Nevada.=20

Moisture will stream ENE across the Great Basin ahead of the
trough to the CO Rockies where Day 2 WPC probabilities of >6" of=20
snow are >50% above 8000ft or so in the Wasatch Front, the Park=20
Range in CO, the Tetons in WY. Precip tapers off Friday afternoon
over the Rockies.

The next wave of precipitation spreads east across CA Friday night
with snow levels around 6500ft. This is the first part of prolonged
precip into CA through at least Monday. Day 3 WPC probabilities=20
for >8" of snow through the period are >50% above about 7000ft on=20
the length of the Sierra Nevada and the CA Cascades/Klamath Mtns.=20


...Columbia Basin and Gorge...
Days 1-2... Maximum impact level from WSSI: Minor

Light precip spreads over the Northwest Thursday before tapering
offs Friday. Sufficient cold air in place looks to make localized=20
light icing in the western Columbia Basin into the Columbia Gorge
where Day 1.5 WPC probabilities for >0.10" ice are now 20-40%.


Jackson=20




...Winter Storm Key Messages are in effect for Snow Squalls tonight
and linked here...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!5OX3cFckbTslL-BxvRSg_xmJKwNMApRf2yOgI7VCdKdSs= r80ePeKcI981KD-2qgLfPPHzgK4cUoYhqwgooy0L3DTPmU$=20



$$

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FOUS11 KWBC 010834
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 AM EST Thu Jan 1 2026

Valid 12Z Thu Jan 01 2026 - 12Z Sun Jan 04 2026

...Eastern Maine...=20
Day 1...

Potent upper trough will swing across New England today, with an
embedded vorticity maxima lifting into the Canadian Maritimes
Thursday night. The evolution of this vorticity max combined with
at least the distant LFQ of a southeast diving upper jet will allow
a surface low to deepen as it tracks across Northern New England,
intensifying more rapidly in response to a negative tilt of the
upper trough this evening into Canada. While in general this=20
system will be progressive, an inverted trough positioned west of=20
the primary low will rotate across eastern Maine as the low shifts=20 northward, leading to a longer duration of moderate to heavy=20
snowfall rates (30-50% chance of 1"/hr). This will result in a=20
swath of moderate snowfall accumulations for which the WPC
probabilities indicate has a moderate chance (50-70%) of exceeding
6 inches, highest across Downeast Maine.


...Great Lakes...
Days 1-3...

An arctic front passing east of the Great Lakes early this morning
will leave impressive CAA in its wake, while cyclonic flow asserts
itself across the region. This cyclonic flow will be secondary
enhanced late Thursday night into Friday as another shortwave
passes through the flow, leading to renewed CAA before shortwave
ridging develops by the end of the forecast period.

While this arctic front will maintain a snow-squall risk through
early this morning into New England and the Mid-Atlantic (for which
Key Messages remain in effect, linked at the bottom of this
discussion) the primary hazard becomes widespread heavy lake effect
snow (LES) in the favored W/NW snow belts. The most intense LES
will likely begin late tonight as 850mb temperatures plummet to as
low as -15C to -20C, across lakes that, while they have cooled,=20
are mostly ice-free. This will lead to impressive SBCAPE as high
5000-1000 J/kg to support a long duration 1-2+"/hr LES event,
especially downwind of Lakes Erie and Ontario due to upstream
connections. The heaviest accumulations D1 and D2 are expected
across the Chautauqua Ridge and along//just barely south of the=20
Tug Hill plateau before shifting a little south into D2. WPC
probabilities are high (>90%) for 6+ inches in these areas D1,
continuing east of Lake Ontario D2. Locally 2-4 feet of snow is
possible east of Lake Ontario before LES wanes during D3. Downwind
of the other Great Lakes, WPC probabilities D1 feature a moderate
risk (50-70%) for 6+ inches in the eastern U.P., but this wanes
quickly during D2.


...California through the Central Rockies...=20
Days 1-3...

A deep trough in the subtropical Eastern Pacific will lift=20
NNE through the central CA coast early today before crossing the=20
Sierra Nevada and into the Great Basin by Friday morning. The
primary shortwave within this trough will crest an expanding ridge
(amplifying downstream of a more intense trough over the Pacific)
and drop into CO and the High Plains Friday morning/aftn.,=20
As the trough moves inland, snow levels on the Sierra Nevada will=20
fall to around 7500ft this afternoon, bringing heavy snow until=20 precipitation ends this evening. Farther east, and continuing
downstream of this trough/impulse, snow levels will remain elevated
at 7000-8000 ft, but precipitation falling as snow will spread
across much of the Great Basin and Four Corners at the higher
elevations. WPC probabilities D1 for 6+ inches of snow reach above
70% in the Sierra, and locally as high as 70% in portions of the
Wasatch and CO Rockies. Precipitation will linger through D2 across
the Four Corners terrain, but with generally a waning trend.

Then on D3 a more pronounced surge of precipitation spreads onshore
CA once again as a deep trough amplifies offshore, resulting in
impressively amplified southerly flow. This will push moisture
onshore as IVT exceeds 500 kg/m/s (>80% chance). Once again snow
levels will be elevated within the accompanying WAA, reaching as
high as 8000 ft into the Sierra (although much lower around 6000 ft
across the Shasta/Trinity region). The pronounced moisture will
result in heavy snow again above these levels, and with SLR
expected to be low, it will be an impactful snowfall due to snow
load. WPC probabilities D3 are high (>90%) for more than 6 inches
across these mountains, with locally more than 12 inches possible
(30-50% chance) in the Sierra.


...Columbia Basin and Gorge...
Day 1...

Increasing southerly mid-level flow over the Pacific Coast will
spread moisture northward, aided by a weakening shortwave lifting
from CA into the northern Great Basin. As this moisture spreads
into the Pacific Northwest, it will overrun a slowly retreating
ridge of high pressure, manifesting with easterly winds draining
into the Columbia Basin/Gorge to maintain cold surface air. This
setup is favorable for light freezing rain with modest accretions
as reflected by WPC probabilities that reach as high as 70% for 0.1
inches of ice. Although amounts are generally light, impacted=20
travel is likely tonight into Friday morning due to slippery=20
roadways.


Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4KcpeRfEaE90L2aFopU7nqHmEr2kAB4kKifoH1AxvdJX1= x1YD-GsTigUG8uJqvwrOLksvrurJKgrhdg4n79dPyZCvaE$=20



$$

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FOUS11 KWBC 012025
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 PM EST Thu Jan 1 2026

Valid 00Z Fri Jan 02 2026 - 00Z Mon Jan 05 2026

...Great Lakes...
Days 1-3...

Persistent west-northwesterly flow continues across the Great
Lakes over the next few days. This is following in the wake of a
strong arctic front that exited the East Coast to kick off the new
year. This cyclonic flow pattern will be enhanced late tonight
into Friday as another shortwave passes through the flow, leading
to renewed CAA before another weak shortwave swings through on
Saturday and ridging finally develops by the end of the forecast
period.

The primary snowfall hazard will be associated with widespread
heavy lake effect snow (LES) in the favored W/NW snow belts. The
most intense LES will likely begin late tonight through Friday
night as 850mb temperatures plummet to as low as -15C to -20C,
across lakes that, while they have cooled, are mostly ice- free.
This will lead to impressive SBCAPE as high 5000-1000 J/kg to
support a long duration 1-2+"/hr LES event, especially downwind of
Lakes Erie and Ontario due to upstream connections. The heaviest
accumulations D1 and D2 are expected across the Chautauqua Ridge
and along/just barely south of the Tug Hill plateau before
shifting a little south into D1.5-D2. WPC probabilities are high

80%) for 6+ inches in these areas D1, continuing east of Lake

Ontario D2. Locally 2-4 feet of additional snow is possible east
of Lake Ontario before heavy LES wanes during late-D2 into D3.
Downwind of the other Great Lakes, WPC probabilities D1 feature a
low risk (20-40%) for 6+ inches in the eastern U.P., but this
wanes quickly during D2.


...Western U.S. Mountain Ranges...
Days 1-3...

Shortwave with subtropical origins will cross over the central
Great Basin tonight and Central Rockies early Friday over an
expanding Rockies upper-level ridge that will help amplify an
eastern Pacific trough over the next few days. Downstream of this
initial shortwave/impulse, snow levels will remain elevated at
7000-9000 ft throughout much of the Great Basin, Four Corners and central/northern Rockies before settling around 70000ft by the end
of D1. WPC probabilities D1 for 6+ inches of snow reach above 70%
in parts of the Wasatch, Central Rockies, and Tetons/Wyoming Range
of the Northern Rockies.

Then on D2-D3 a more pronounced surge of precipitation spreads
onshore CA once again as a deep trough amplifies offshore,
resulting in impressively amplified southerly flow. This will push
moisture onshore as IVT exceeds 500 kg/m/s (>80% chance). Once
again snow levels will be elevated within the accompanying WAA,
reaching as high as 8000 ft into the Sierra (although much lower
around 6000 ft across the Shasta/Trinity region). The pronounced
moisture will result in heavy snow again above these levels, and
with SLR expected to be low, it will be an impactful snowfall due
to snow load. Precipitation will also reach northward along the
West Coast mountains to the Cascades and inland across the Great
Basin towards the favorable upslope southwest facing terrain. Snow
levels will remain around 6000ft across these regions, with lower
levels (around 4000-5000ft) in the Cascades. WPC probabilities
D2-D3 are high (>70%) for more than 6 inches across the Sierra and
northern CA ranges, as well as the WA Cascades, Sawtooths of ID,
and Tetons of WY. More than two feet of snow is likely (70-90%)
over the next three days in the Sierra.


...Columbia Basin and Gorge...
Day 1...

Increasing southerly mid-level flow over the Pacific Coast will
continue to spread moisture northward tonight, aided by a
weakening shortwave lifting from CA into the northern Great Basin.
As this moisture spreads into the Pacific Northwest, it will
overrun a slowly retreating ridge of high pressure, manifesting
with easterly winds draining into the Columbia Basin/Gorge to
maintain cold surface air. This setup is favorable for light
freezing rain with modest accretions as reflected by WPC
probabilities that reach 20-40% for 0.1 inches of ice after 00Z
this evening. Although amounts are generally light, impacted
travel is likely tonight into Friday morning due to slippery
roadways.


Weiss/Snell



$$

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FOUS11 KWBC 020753
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 AM EST Fri Jan 2 2026

Valid 12Z Fri Jan 02 2026 - 12Z Mon Jan 05 2026

...Great Lakes...
Days 1-3...

Ongoing lake effect snow (LES) Will continue in earnest today,
especially across the eastern U.P., and downwind of Lakes Erie and
Ontario. This LES will be driven by persistent CAA across the
lakes, leading to steep lapse rates and inversion depths that climb
towards 800mb, leading to 500-750 J/kg of lake-induced instability.
While the mean low-level flow will be a bit more W than NW, this
will help tap an upstream connection from Superior, across Huron,
and towards Lake Ontario, indicating the heaviest snowfall will
likely be along and south of the Tug Hill Plateau through D1 and
into D2 before winding down in response to brief shortwave ridging.
While periods of heavy snow are also likely in portions of the
northern L.P. and along the Chautauqua ridge, the persistence and
intensity of this snowfall should be less. This is reflected by WPC probabilities for 4+ inches on D1 that area 30-50% in the eastern
U.P. and along the Chautauqua Ridge, but above 90% east of Lake
Ontario, where locally 2+ feet is likely on D1. During D2 the
intensity and coverage of LES wanes, but WPC probabilities for 4+
inches remain above 50% near Oswego, NY.

After a brief respite in response to the aforementioned shortwave
ridging, two separate, but fast moving, shortwaves will crest the
ridge to the west and dive rapidly from Saskatchewan/Alberta across
the Great Lakes. The first of these will race southeast Saturday
aftn/night, and while some enhanced ascent and subtly increased
moisture will result in light synoptic snowfall, additional
accumulations from eastern MN through western NY should be minimal.

A more substantial impulse will then drop southeast in a similar
fashion Sunday night, but this impulse will be accompanied by
greater moisture as it originates from the Pacific and ejects from
the Northern Plains rather than central Canada. This will again be
fast moving, but will have more pronounced synoptic lift in
response to height falls, PVA, LFQ jet diffluence, and more robust
850mb WAA leading to enhanced fgen. At this time, the speed of the
system is expected to limit total snowfall, but briefly heavy snow
rates thanks to idealized ascent into the DGZ could produce a
narrow swath of more than 4 inches as reflected by WPC
probabilities that are as high as 50-70% for 4+ inches from near
Duluth, MN eastward through much of the U.P and the neighboring
portions of WI.


...Western U.S. Mountain Ranges...
Days 1-3...

An active period of weather continues across much of the West as
Pacific moisture repeatedly surges onshore in response to
persistent troughing offshore.

For D1, a brief period of ridging will blossom along the Pacific
Coast, but downstream into the Intermountain West a shortwave with
Pacific origin will lift steadily northeast while de-amplifying.
This will result in a stripe of precipitation arcing from the
Northern to the Central Rockies, and falling as snow above
6000-7000 ft. WPC probabilities D1 reach above 70% for 6+ inches
near the Tetons of WY and the Park Range of CO, with more
widespread elevated probabilities for 4+ inches across much of the
rest of the terrain in this region.

Then beginning late D1 and continuing into D3, much more pronounced
moisture begins to pivot onshore the Pacific Coast. This will be in
response to an impressive trough aligned just offshore, from which
a surface low will track northeast towards WA state by Sunday
morning, with a secondary wave tracking towards northern CA Sunday
aftn. While these surface lows will help enhance local ascent, in
general moisture will be pronounced across much of the West due to
increasing southerly flow downstream of the primary trough axis
pushing IVT well onshore with magnitudes above 500 kg/m/s. As is
typical with strong IVT plumes, they will be driven both by Pacific
jet energy and warm advection, resulting in elevated snow levels
climbing to 7000-9000 ft ahead of the first wave, and while they
will rise again with the secondary wave, they will generally be
much lower, 5000-7000 ft on D3, even lower, around 3500 ft, in the
Cascades and interior Northwest.

Any ascent forced through synoptic features or upslope enhancement
will cause rounds of heavy snowfall above these elevations both
Saturday and Sunday. WPC probabilities steadily increase and expand
through the weekend, with widespread high chances (>70%) for 4+
inches reaching from the Olympics, along the entirety of the
Cascades, the Shasta region, the Sierra, and through much of the Northern/Central Rockies and into the Wasatch, by Monday morning.
While the heaviest snowfall is likely in the Sierra where many
locations above 6000 ft could experience 2-5 feet of snow, much of
the higher terrain of the West could receive 1-2 feet before
coverage wanes just beyond D3. This will likely bring considerable
impacts to the higher elevations due to generally low SLR snow,
with difficult travel likely across the Sierra Passes.


...Central Plains...
Day 1...

A fast moving clipper rounding the western ridge and dropping
southeast over the Central Plains today will be of subtropical
origin. Although this feature will be progressive and of modest
amplitude as it weakens, it will produce sufficient ascent into a
moistening column to produce a narrow corridor of mixed
precipitation in the vicinity of northeast Nebraska. While total
precipitation will be modest, WPC probabilities indicate a 70-90%
chance of at least 0.01" of freezing rain, with locally up to 0.1"
of ice possible leading to hazardous travel.


Weiss



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FOUS11 KWBC 021934
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
234 PM EST Fri Jan 2 2026

Valid 00Z Sat Jan 03 2026 - 00Z Tue Jan 06 2026

...Central Plains...
Day 1...

A fast moving clipper rounding the western ridge and dropping
southeast over the Central Plains today will have sufficient 290K
isentropic ascent and 850mb WAA to foster precipitation over
eastern NE and as far east the lower MO River Valley. Soundings
show a pronounced warm nose between 850-750mb to cause a wintry mix
with surface-850mb temps sub-freezing. WPC probabilities indicate
a 70-90% chance of at least 0.01" of freezing rain, with locally up
to 0.1" of ice possible leading to hazardous travel. The WSSI does
depict Minor Impacts from Ainsworth on south and east to US routes
30 and 81 near Columbus, suggesting hazardous travel is a concern
in these areas through this evening. There is the potential for
some travel impacts all the way to the MO River, including the
Omaha metro area this evening.


...Lake Effect Snow...
Days 1-2...

Ongoing lake effect snow (LES) will continue this afternoon,
especially across the eastern U.P., and downwind of Lakes Erie and
Ontario. This LES will be driven by persistent CAA across the
lakes, leading to steep lapse rates and inversion depths that climb
towards 800mb, leading to 500-750 J/kg of lake-induced
instability. While the mean low-level flow will be a bit more W
than NW, this will help tap an upstream connection from Superior,
across Huron, and towards Lake Ontario, indicating the heaviest
snowfall will likely be along and south of the Tug Hill Plateau
through D1 and into D2 before winding down in response to brief
shortwave ridging. While periods of heavy snow are also likely in
portions of the northern L.P. and along the Chautauqua ridge, the
persistence and intensity of this snowfall should be less. This is
reflected by WPC probabilities showing moderate-to-high chances
(50-70%) for 4+ inches through Saturday over the eastern U.P. and
along the Chautauqua Ridge. The heaviest snowfall will be downwind
of Lake Ontario through Saturday with additional snowfall totals of
12-20" around Oswego, NY.

After a brief respite in response to the aforementioned shortwave
ridging, two separate, but fast moving, shortwaves will crest the
ridge to the west and dive rapidly from Saskatchewan/Alberta across
the Great Lakes. The first of these will race southeast Saturday
aftn/night, and while some enhanced ascent and subtly increased
moisture will result in light synoptic snowfall, additional
accumulations from eastern MN through western NY should be minimal.


...Upper Midwest...
Days 2-3...

One of the 500mb disturbances responsible for heavy mountain snow
in the West will round the ridge axis over the southern Plains and
head for the Upper Midwest on Sunday. The Upper Midwest lies
beneath a coupling 250mb jet streak structure that coincides with
500mb PVA and 700mb Q-vector convergence Sunday afternoon that then
moves over the Great Lakes Sunday night. In addition to the synoptic-
scale ascent aloft, strengthening 850-700mb WAA and FGEN will give
rise to a band of heavy snow from northern MN and northern WI
Sunday afternoon to the Upper Great Lakes Sunday night. There is
likely to be a >0C warm nose in southern ND, central MN, and
southern WI that leads to an icy wintry mix. As the 500mb vort max
moves east Sunday night, it will run into a stronger confluent zone
over Ontario that shears out the disturbance and leads to
lessening snowfall rates. By Monday morning, periods of snow will
envelope Upstate NY and reach as far inland as the northern
Appalachians, but snow will generally be on the lighter side with
the upper-level forcing weakening.

WPC probabilities show low-to-moderate chances (30-50)% for 24-hour
snowfall totals >4" over the heart of MI's Upper Peninsula.
Localized totals >6" are likely, especially given the favorable
meteorological drivers that are at play. Many deterministic
members do show a swath of >6" of snow, but given the wide cast of
potential QPF totals and the different placement of the band, it is
leading to greater dispersion in ensemble mean guidance. At this
time, residents from northern MN and northern WI to the MI U.P. and
tip of MI's Mitten should prepare for at least Minor Impacts.
WPC's WSSI-P does show low-to-moderate chances (30-50%) for Minor
Impacts in the Lower MI U.P. and northeast WI. The WSSI-P also
shows low chances (10-30%) for Minor Impacts (hazardous travel
conditions) over western WI and central MN due to ice
accumulations.


...Western U.S. Mountain Ranges...
Days 1-3...

An active weather pattern continues across much of the West as
repeated rounds of Pacific moisture surge onshore and advance
eastward across the Rockies.

An anchored troughing pattern along the west coast of North
America is forecast to continue for several more days. This
anomalous longwave trough, paired with a strong ridge over Mexico,
is supporting steadfast SWrly flow out of the Pacific that is
supplying copious amounts of moisture over the western-third of the
CONUS. As snow over the central Rockies dissipates this afternoon,
an upper-level ridge axis over the Great Basin will slide east
thanks to the approach of a large upper-low west of CA. An
expansive IVT, with moisture originating out of the subtropics,
will surpass 500 kg/m/s and extend almost the full length of the
U.S. West Coast tonight. This moisture plume will be heaviest along
the track of a frontal system (low 980s low west of OR) that slams
into the West Coast tonight and early Saturday morning. While this
system has a good deal of moisture at its disposal, their is a
significant lack of a continental polar (cP) air-mass ahead of the
storm. Still, the combination of upslope enhancement and persistent
500mb PVA when paired with the onslaught of Pacific moisture will
foster mountain snow throughout much of the West this week.

Snow levels throughout CA will initially be in the 7000-9000ft
range ahead of this first system (higher snow levels farther
south), but as subsequent upper- level disturbances approach as
they round the base of the longwave trough positioned off the West
Coast, 500-700mb height falls and CAA should result in snow levels
coming down to the 5000-7000ft late Saturday and to close out the
weekend. Snow levels will be a little lower in the Pacific
Northwest and northern Rockies, but most snowfall will still reside
in the more remote reaches of these mountains ranges with some
welcomed snow to ski resorts in these regions. That said, the
bigger impacts will be in the Sierra Nevada where low SLR's and
steadily lowering snow levels should prompt heavy snow for many of
the mountain range's passes.

Snowfall totals above 6,000ft in the Sierra Nevada, over the next
three days, are likely to range between 2-5 feet with localized
amounts in the higher peaks of the southern Sierra Nevada topping 6
feet. The WSSI is lit up with Major to even Extreme Impacts due to
Snow Amount, with the I-80 portion beginning near Truckee on west
to around mile marker 158, likely to see significant travel
impacts beginning Saturday night and continuing into Sunday.
Farther north, WPC probabilities show high chances (>70%) for
snowfall totals >4" in the Cascades, Olympics, and on south to the Siskiyou/Shasta mountains of northern CA. Farther east, snowfall on
the order of 8-12" are likely in the Lewis Range, Blue, and
Sawtooth Mountains above 6000ft, the Tetons, Absaroka, and Bear
River above 7000ft, and the Wind River and Uinta/Wasatch above
8,000ft. The Sawtooth, Tetons, Wind River, and Bear River Ranges
all sport high chances (>70%) for snowfall totals >12" with some
localized totals topping 24" expected.


Mullinax/Weiss



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FOUS11 KWBC 030716
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
216 AM EST Sat Jan 3 2026

Valid 12Z Sat Jan 03 2026 - 12Z Tue Jan 06 2026


...Upper Midwest/Great Lakes...
Days 1-3...

Impressive lake effect snow (LES) will continue today, especially
across the U.P. of MI and downwind of Lakes Erie and Ontario. This
LES has already been impressive, with 24-36 hour snowfall of 1-3
feet or more in some areas east of Lake Ontario, and today's LES
will likely be heavy once again. Continued CAA, reinforced at least
slightly by a weak shortwave moving overhead, will maintain steep
lapse rates and lake-induced instability to support snowfall rates
of 1-2"/hr as reflected by HREF 1"/hr snowfall probabilities
above 40%. A more NNW wind shift behind this shortwave will cause
bands to drop a little south of the recent heavy snowfall, and
WPC probabilities for an additional 4+ inches peak above 70%
southeast of Lake Ontario, with lower potential (10-50% chance)
across the eastern U.P. of MI and near the southtowns of Buffalo,
NY to the Chautauqua Ridge.

Thereafter, brief shortwave ridging envelops the region before a
more significant shortwave crests the western ridge and races
eastward towards the Great Lakes. This impulse will be of Pacific
origin, and accompanying elevated moisture (PWs above 0.5" and the
90th climatological percentile) will track in tandem with this
feature. Forcing for ascent driven by height falls/PVA,
intensifying left-exit jet level diffluence, and strengthening WAA
will provide the impetus for heavy snowfall, with 1"/hr snowfall
rates likely within any banded structures. The system will remain
progressive, and the guidance has trended a little SW over the past
few runs, but accompanying NBM probabilities have been relatively
steady. This indicates increasing confidence for a narrow swath of
heavy snowfall, for which WPC probabilities indicate a moderate
risk (50-70%) for 4+ inches across the U.P. of MI D2 into D3, with
several inches likely as well from near Duluth, MN through the
northern L.P. of MI.

Additionally, on the southern edge of this precipitation swath,
some mixed freezing rain/sleet is likely as the warm nose edges
northward in response to the pronounced WAA. This could result in a
corridor of impactful icing from far eastern ND through
central/southern MN and into southern WI. Although WPC
probabilities for 0.1" of ice are less than 10%, some icy roadways
and hazardous travel are possible Sunday evening.


...Western U.S. Mountain Ranges...
Days 1-3...

A persistent mid-level trough positioned west of the Pacific Coast
will periodically shed impulses northeast and onshore, with each
subsequent impulse spreading energy across most of the
Intermountain West.

This persistent trough will manifest with 850-500mb heights that
will remain at or below the 10th climatological percentile into
Monday before finally relaxing. As spokes of vorticity swing out
from this trough and push onshore (the first likely this aftn with
a secondary impulse lifting northeast on Sunday night), the
subtropical origin will expand anomalous moisture onshore thanks to
surges of elevated IVT. As is typical with this setup, the
corresponding WAA will help drive snow levels upward, but a series
of cold front accompanying the aforementioned impulses will temper
the overall warming, leading to a general slow drop in snow levels
through the period. By Tuesday, as the core of the trough finally
pivots towards CA, snow levels could be quite low in the Cascades
and Pacific Northwest, only 1500-2500 ft, and just 3000-5000 ft
elsewhere after being as high as 6000-8000 ft to start the forecast
period. This suggests that each wave of precipitation through the
forecast period will result in more expansive and impactful snow at
lower elevations.

During D1, the heaviest snowfall is expected in the Sierra and
northern CA terrain where WPC probabilities for 12+ inches reach
70-90+ percent, and 1-3 feet is likely above 6000 ft. WPC
probabilities for 6+ inches D1 of more than 50% cover a large
portion of the Intermountain West terrain as well, with locally 1
foot possible in parts of the Wind Rivers, Sawtooth/Salmon River
ranges, and Cascades. During D2, waves of precipitation continue,
and support another day of heavy snow, focused across the Sierra
and Shasta/Trinity area, with lighter accumulations elsewhere, but
still covering much of the terrain from the Wasatch/Uintas and
points north and west. Multiple feet of snow is again expected in
the Sierra (WPC probabilities for 12+ inches above 90%) with more
than 1 foot possible in the higher terrain of the northern
UT/western WY, and into ID. Finally on D3, precipitation intensity
wanes, but additional significant snowfall accumulations are likely
in much of the area as this prolonged event begins to wane.

With extremely heavy snow likely in the Sierra and northern CA
mountains, totaling 4-6+ feet in some areas, and snow levels
falling below pass levels, travel will become extremely challenging
into early next week, and extreme impacts are possible due to the
combination of heavy snow and low SLR.


Weiss

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FOUS11 KWBC 032058
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
358 PM EST Sat Jan 3 2026

Valid 00Z Sun Jan 04 2026 - 00Z Wed Jan 07 2026


...Northern Plains/Upper Midwest/Great Lakes/Interior Northeast...
Days 1-3...

Single band lake effect snow from Lake Ontario is forecast to sag
south as it eases in intensity into the evening the latest clipper
(this one perhaps the weakest this week) works its way east from
Michigan.

The next clipper of Pacific origin and crosses the northern Plains
early Sunday with widespread wintry precip breaking out around
midday near the MN/Dakotas border. Elevated moisture (PWs above
0.5" and the 90th climatological percentile), ascent driven by
height falls/PVA, intensifying left-exit jet level diffluence, and strengthening WAA will accompany this feature. Rates quickly become
heavy over northern MN Sunday afternoon with a wintry mix on the
southern edge of the precip, but mostly snow, heavy at times with

1"/hr rates (per the 12Z HREF) within banded structures. The

system will remain progressive, with a preference for QPF from the
wetter global models vs the CAMs which have a narrower precip
shield as often has on synoptically forced winter storms. The risk
for 6" through Sunday night has risen over northern MI with Day 1.5
PWPF now around 35% around both sides of the Straits of Mackinac.
Day 1.5 probs for >4" are over 30% from the Bayfield Peninsula of
WI across the U.P. and Upper L.P. along with far northern WI and
northern Door Co.

The strong warm nose could result in a corridor of impactful icing
over central MN (including the Twin Cities metro) and
western/central WI. WPC ice probabilities for >0.1" remain less
than 10%, but some icy roadways and hazardous travel are possible
Sunday afternoon and evening.

This wave tracks into New York Monday before weakening as it
continues to push into a ridge. Day 2 PWPF for >4" is limited to
around 30% for the Tug Hill Plateau where some lake enhancement can
be expected on westerly low level flow.

The next wave is southern stream, coming from CA and crossing
Nebraska/Iowa Monday night. The northern precip shield should bring
mainly light to moderate wintry mix over central MN and northern
WI into Tuesday. While 12Z guidance generally agrees on a narrow
swath of mainly freezing rain, there is still meridional
differences of central vs northern WI. Even the 12Z EC-AIFS shifted
north with its QPF axis (northern WI) from the 06Z run (which
favored north-central WI). So stay tuned on Tuesday icing threats
for the Upper Midwest.



...Western U.S. Mountain Ranges...
Days 1-3...

A persistent longwave trough positioned off the Pacific Coast will
continued to shed impulses onshore at least through Monday night,
with each subsequent impulse spreading energy across most of the
Intermountain West.

The southern stream trough off CA with the northern stream end
shifting over the Northwest will maintain 850-500mb heights at or
below the 10th climatological percentile into Monday before finally
relaxing as the southern stream low likely closes off west of CA.
Pacific moisture flows inland on WAA ahead of the main trough axis,
but lowering height falls will allow lower snow levels to continue
shifting across the West.

Sierra Nevada...Days 1/2...

The current trough pushing into OR/northern CA this afternoon
shifts south across CA through Sunday with the heaviest precip on
the Sierra Nevada. Snow levels drop to around 6000ft tonight on
along the length of the Sierra Nevada and even drop to around
6500ft in the SoCal ranges Sunday.

The next wave is the northern stream that shifts into the OR/WA
coast Sunday and works its way down through central CA into Monday
night before focusing offshore. Snow levels on the Sierra Nevada
are lower with the next wave, generally around 5000ft, but drop to
around 4500ft Monday evening though snow rates will be less than
from the current wave.

Day 1 PWPF for >24" is 50-80% above 7000ft across the length of the
Sierra Nevada. Then for Day 2 the PWPF for additional >12" over
the length of the Sierra Nevada is 50-80% above about 6500ft.

With prolonged heavy snow for the Sierra and northern CA
mountains, totaling 4-6+ feet in some areas, and snow levels
below pass levels, travel will remain extremely challenging through
Monday. Localized extreme impacts are possible due to the
combination of heavy snow and low SLR.

Cascades...Days 1-3...
Repeating waves into the Pacific Northwest through Sunday evening
maintain moderate to heavy snow rates on the WA/OR Cascades with
snow levels remaining around 4000/5000ft tonight. As the northern
stream shortwave trough pushes through later Sunday, the snow
levels drop to 3000/4000ft before rates ease Sunday night. Day 1
PWPF for >8" is 50-80% in the higher Cascades with 40-70% for >6"
on Day 2.
There's a lull for the Cascades then through Monday night before
the next northern stream trough approaches Washington with snow
levels starting on the WA Cascades around 1200ft Tuesday morning,
rising to around 2500ft by Tuesday evening. Day 3 probs for >6" are
50-90% throughout the WA Cascades and Olympics above about 2500ft.


Northern to Central Rockies...
Days 1-3...

The current lull over the northern Rockies ends by this evening as
moisture streaming from CA flows across ID and western MT/WY
through tonight before drifting south to UT/southern WY Sunday
night. Snow levels begin around 6000ft at onset and drop to around
5000ft Sunday (3000-4000ft for northern ID/MT). Day 1 snow probs
for >8" are 50-80% in the central ID and western WY ranges as well
as around Glacier NP and west through northern ID. The focus shifts
south a bit for Day 2 where probs for >8" are 50-80% for the
Wasatch Front and Uinta as well as the Wind River again in WY while
central ID values are around 50%.

Day 3 probabilities are lower across the Rockies as rates decrease
under weakening flow. Probs for >6" are 50-80% in the Tetons and
40-60% in the Park Range of CO, the Wind Rivers, central ID up
through the Bitterroots.


Jackson


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FOUS11 KWBC 040819
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
319 AM EST Sun Jan 4 2026

Valid 12Z Sun Jan 04 2026 - 12Z Wed Jan 07 2026


...Northern Plains/Upper Midwest/Great Lakes/Interior Northeast...
Days 1-3...

Some modest lake effect snow (LES) will continue through Sunday
aftn, but primarily within a single band south/southeast of Lake
Ontario with upstream connection to Lakes Huron and Superior.
Additional snowfall across this region should be light as reflected
by WPC probabilities for an additional 2+" of just 10-30%,
although brief 1"/hr rates are possible (10-30% chance).

Thereafter, the mid-level pattern flattens a bit as shortwave
ridging expands from the west, leading to pinched and more
progressive flow across the region. Within this flow, two back-to-
back shortwaves will traverse the region bringing rounds of wintry
weather.

The first of these will emerge from the High Plains Sunday morning
and push due east across the Great Lakes in a de-amplifying manner
as it becomes absorbed into the pinched westerlies. Despite the
weakening amplitude, height falls, PVA, and the left-exit region of
a strengthening jet streak will produce deep layer ascent, and
the intensification of this jet streak will likely result in
enhanced omega despite the weakening amplitude of the shortwave. At
the same time, increasing and impressive 925-850mb WAA will spread
northeast ahead of this impulse, aligning with the best left-exit
dynamics and the associated response to produce impressive fgen but
with limited temporal duration. Since this feature will be of
Pacific origin, the accompanying moisture will be impressive as
reflected by NAEFS PWs that are above the 97th percentile, aligned
with the strongest ascent. This suggests that as precipitation
expands from MN through the U.P., and into the northern L.P., a
narrow band of heavy snow will develop which has a 60-80% chance
of producing 1"/hr snowfall rates. The duration of these will,
again, be limited to the progressive nature of the wave, but WPC
probabilities for 4+ inches are above 50% from the Arrowhead of MN
eastward through the northern L.P. of MI, with locally 6-8"
possible (30% chance) in portions of the eastern U.P.

Additionally, south of this axis of heavy snow, a corridor of
modest mixed precipitation, including freezing rain, is likely as
the WAA surges a warm nose to around +3C at 850-800mb. The
refreezing layer is quite deep, so this may manifest more as sleet
than freezing rain, but hazardous travel is Sunday evening from MN
through central WI where WPC probabilities for 0.01" of ice are
50-70%.

This lead wave will continue to track into New England before
exiting to the Atlantic Monday night, but additional snowfall is
expected to be light, generally 1-3", although locally higher in
the Tug Hill Plateau through lake enhancement, as ascent weakens.

The next shortwave follows quickly in the wake of the first, and
emerges from CA Sunday evening before racing to reach the Corn Belt
by Tuesday morning. This impulse will track along the southern
subtropical jet, which is progged to intensify over the Central
Plains, reaching towards 140 kts. The favorable overlap of the LFQ
and height falls downstream of the shortwave will likely lead to
surface low pressure development Monday night near Iowa, with this
low then tracking steadily northeast into Ontario by Tuesday
evening. While there is still some spatial spread in the placement
of this low according to the different ensemble clusters, the
increasing ascent will lead to another round of wintry
precipitation from Minnesota through the Great Lakes (where a mix
of freezing rain and snow is likely), with additional mixed
precipitation spreading into New England by the end of the forecast
period. Total ascent with this secondary wave should be less
intense than the lead wave, and the thermal evolution is quite
complex due to potential secondary low development in the Gulf of
Maine, but at this time WPC probabilities for 2+ inches of snow are
just 10-30% in the higher elevations of Upstate NY and northern New
England.

For the freezing rain, WPC probabilities indicate a high risk

70% chance) of at least 0.01" of ice from central MN near the

Twin Cities through much of WI and MI, and into central and
northern New England. The greatest risk for at least 0.1" of ice is
likely in parts of northern WI, northern MI, and the higher
elevations of the Catskills, Adirondacks, and southern Greens.


...Western U.S. Mountain Ranges...
Days 1-2...

The active west continues into early next week as an anomalous
trough persists just off the Pacific coast through Tuesday morning
before amplifying into a closed low which then undercuts towards
Baja by the end of the forecast period.

Downstream of this trough, nearly continuous S/SW flow will shed
spokes of vorticity onshore, with the accompanying height falls/PVA
leading to rounds of precipitation across much of the western
CONUS. At the same time, a subtropical jet will amplify and waver
from CA through the Central Plains, providing additionally enhanced
ascent. The combination of persistent SW mid-level flow with the
wavering jet stream will surge periods of elevated IVT onshore,
resulting in PW plumes that occasionally exceed the 90th
climatological percentile. While there may be periods of enhanced
ascent locally across different regions, in general the next 48
hours appear to be synoptically forced with broad large-scale
ascent, locally enhanced through PVA where the vorticity lobes
stream overhead, and through upslope enhancement. The strongest
upslope flow continues to be appear focused over the Sierra where
snowfall will be prolific, but heavy snow is likely through Monday
night across much of the region.

With broad SW flow encompassing the region, the accompanying WAA
will surge snow levels to as high as 6000-8000 ft in the Great
Basin and Rockies D1 (but generally 3000-5000 ft elsewhere), before
steadily falling through D2 as a cold front pushes eastward and the
trough axis finally swings farther east to the coast. By 12Z
Tuesday, snow levels are expected to be generally 1500-2500 ft in
the north, to 5000-6000 ft in the south. 2-day WPC probabilities
(12Z Sunday through 12Z Tuesday) feature a high risk (>70% chance)
for 12+ inches in the Sierra, northern CA ranges, Uintas, Tetons,
Wind Rivers, and portions of the Salmon River/Sawtooth/Bitterroots,
with lesser snowfall expected at the other regional terrain. In
the Sierra, 2-4 feet is possible in the higher elevations.


...Cascades...
Day 3..

Mid-level flow across the Northern Pacific will become pinched and
zonal Tuesday, while a weak impulses approaches the coast and may
move onshore overnight into Wednesday morning. This zonal mid-level
flow will be topped by a strengthening Pacific jet streak which
will drop gradually southward such that the overlap of PVA/height
falls will match the greatest LFQ diffluence to provide ample
ascent. This will be aided by upslope enhancement into the terrain
thanks to the westerly flow, producing brief but impressive deep
layer lift into IVT that has a >80% chance of exceeding 250 kg/m/s.
While westerly IVT does not usually result in as impressive of
precipitation as that with a S or SW component, a fully saturated
column with steepening lapse rates will result leading to a period
of heavy snow in the Olympics and Cascades of OR and WA. Snow
levels will be generally 2000-3000 ft during this time, so pass
level impacts leading to hazardous travel are expected. WPC
probabilities for more than 8 inches of snow reach 70+%, with more
than 1 foot possible at the passes (Snoqualmie and Stevens
included).



Weiss


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FOUS11 KWBC 041921
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
221 PM EST Sun Jan 4 2026

Valid 00Z Mon Jan 05 2026 - 00Z Thu Jan 08 2026


...Upper Midwest/Great Lakes/Interior Northeast...
Days 1-3...

Over the next few days, two back-to-back progressive shortwave
troughs will bring a combination of snow and ice to the Upper
Midwest, Great Lakes, and interior Northeast.

The first disturbance is making its way over the Upper Midwest and
this afternoon and will be positioned over the Great Lakes tonight.
500mb height falls, sufficient PVA, and the left-exit region of a
strengthening jet streak will produce deep layer ascent. At the
same time, increasing and impressive 925-700mb WAA will spread
northeast ahead of the shortwave trough, creating a narrow FGEN
band over northern WI and the MI U.P. this evening. Moisture
associated with this feature comes from the highly active Pacific
jet stream pattern, reflected by NAEFS PWs that are above the 97th
percentile. With these synoptic and mesoscale ingredients at play,
a narrow band of heavy snow will develop which, according to latest
12Z HREF guidance, show high chances (>70%) of producing at least
1"/hr snowfall rates from far northern WI to the southern periphery
of MI's U.P. and the Tip of MI's Mitten this evening. Duration
will be limited given the upper-level disturbance's progressive
nature, but WPC probabilities for 4+ inches are above 50% from the
central MI U.P. to the tip of MI's Mitten, with locally 6-8"
possible (30-50% chance) in portions of the eastern U.P..

Farther south, an icy wintry mix is likely as WAA produces a warm
nose to around +3C at 850-750mb. The refreezing layer is quite deep
below 850mb, so some sleet may help to cut into the freezing rain accumulations. Nevertheless, hazardous travel is expected this
evening from northern MN through central WI and central MI where
WPC probabilities for 0.01" of ice are 50-70%.

This first shortwave trough will race into the Northeast before
exiting to the Atlantic Monday night, but snowfall is expected to
be light. Snowfall totals over northern NY and as far east as the
Green Mountains are likely to receive 1-3" of snowfall, although
locally higher in the Tug Hill Plateau due to lake enhancement is
possible.

As snow concludes across the Northeast Monday afternoon, the next
Pacific shortwave reaches the Corn Belt Monday night. This
disturbance will have sufficient synoptic-scale forcing thanks to
a strengthening subtropical jet streak that strengthens to the tune
of 140 kts. Left-exit region dynamics and height falls downstream
of the shortwave will spawn low pressure over eastern NE Monday
evening, with the low then tracking east across the Midwest
Tuesday morning and over southern Ontario by Tuesday evening. There
remains some uncertainty on the placement of the heaviest QPF, but
increasing ascent will foster another round of wintry
precipitation from Minnesota through the Great Lakes Monday night
into Tuesday. As the low reaches southern Ontario Tuesday evening,
additional mixed precipitation spreads across New England Tuesday
night and into Wednesday. Northern New England has the better odds
for light-to- moderate snowfall on Wednesday as a coastal low may
support a deformation zone of snowfall that produces 1-4" of
snowfall.

While the first system had a fair amount of snowfall over the Upper
Great Lakes, the second system from the Midwest and Great Lakes to
the interior Northeast will largely be an ice producer. WPC
probabilities indicate a high risk (>70% chance) of at least 0.01"
of ice from central MN near the Twin Cities through the heart of
the Great Lakes and into the higher terrain of the interior
Northeast. The greatest risk for at least 0.1" of ice is likely in
parts of central MN, northern WI, and the higher elevations of the
Catskills, Adirondacks, and southern Greens.


...Western U.S. Mountain Ranges...
Days 1-2...

The active west continues into the first half of the week as an
anomalous trough persists just off the Pacific coast through
Tuesday morning before amplifying into a closed low that heads
towards Baja by Wednesday. This should conclude the snow in the
Sierra Nevada by Tuesday, but lingering snow in the Northern
Rockies will continue into Wednesday.

Downstream of this trough, nearly continuous S/SW flow will shed
spokes of vorticity onshore, with the accompanying height falls/PVA
leading to rounds of precipitation across much of the western
CONUS. At the same time, a subtropical jet will amplify and waver
from CA through the Central Plains, providing additional
synoptically-induced ascent. The combination of persistent SW mid-
level flow will foster elevated IVT today and into Monday,
resulting in PW plumes that occasionally exceed the 90th
climatological percentile. While periods of enhanced ascent
will differ across different regions, the next 36-48 hours appear
to be synoptically forced with broad large-scale ascent and
through upslope enhancement. The strongest upslope flow continues
to be appear focused over the Sierra Nevada through tonight where
snowfall will be prolific at times, but heavy snow is likely to
wind down late Monday as the upper low pinches off from the polar
jet and dives south of CA Monday night.

With broad SW flow engulfing the region, ongoing WAA will surge
snow levels to as high as 6000-8000 ft in the Great Basin and
Rockies D1 (but generally 3000-5000 ft elsewhere), before steadily
falling through D2 as a cold front pushes eastward and the trough
axis finally swings farther east to the coast. By 12Z Tuesday, snow
levels are expected to be generally 1500-2500 ft in the north, to
5000-6000 ft in the south. 2-day WPC probabilities (00Z Monday
through 00Z Wednesday) feature a high risk (>70% chance) for 12+
inches in the Sierra, northern CA ranges, Uintas, Tetons, Wind
Rivers, and portions of the Salmon River/Sawtooth/Bitterroots, with
lesser snowfall expected at the other regional terrain. In the
Sierra, an additional 1-2 feet is expected in the higher
elevations.


...Cascades & Olympics...
Days 2-3...

A powerful storm system traversing southern AK and an unusually
strong subtropical ridge north of Hawaii will create a strong
thermal gradient that that directs a strong >140kt 250mb jet
streak at the Pacific NW. The Olympics and Cascades will reside
beneath the left-exit region of this jet streak at the same time as
500mb height falls unfold on Tuesday. Between falling heights and
upslope enhancement driven by a westerly IVT topping 300 kg/m/s,
snow levels will fall to as low as 2,000ft Tuesday night in the WA
Cascades and Olympics and 3,000ft in the OR Cascades. By Wednesday,
a secondary disturbance ejecting out of the Gulf of AK trough will
bring another round of mountain snow to the Cascades on Wednesday.
WPC probabilities show high chances (>70%) for snowfall >12" above
3,000ft in the Cascades and Olympics with 2-4 feet of snow likely
in the northern WA Cascades above 4,000ft. Expect impacts at pass-
level in WA as the WSSI currently shows Moderate Impacts (hazardous
driving conditions and potential closures) for Snoqualmie and
Stevens Passes where as much as 1-2 feet of snowfall is forecast.
Note that the WSSI-P shows low-to-moderate chances (20-40%) for
locally Major Impacts, which imply increased odds for closures and
delays at these passes.


Weiss/Mullinax





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FOUS11 KWBC 050758
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Mon Jan 5 2026

Valid 12Z Mon Jan 05 2026 - 12Z Thu Jan 08 2026


...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

Shortwave currently over Wisconsin will track rapidly eastward
while continuing to de-amplify this morning, likely moving off the
Maine coast by Tuesday morning. The weakening trend of this impulse
driven by the absorption into more pinched westerlies will
gradually weaken ascent such that ongoing heavy snow near the Great
Lakes will transition to primarily light snow from Upstate NY
through central/northern New England. Light accumulations of 1-3"
are expected in this region, with locally as much as 4" possible in
the Tug Hill Plateau due to lake enhancement and southern Greens
thanks to upslope flow. In general, however, the most substantial
impacts from this shortwave will end before the new D1 period
begins.

Almost as quickly as this first shortwave exits New England, a
second impulse following quickly in its wake will begin to
organize over the Upper Midwest Tuesday morning. This next impulse
stems from a weak vorticity lobe which ejected from the Pacific
trough late Sunday, crested the western ridge, and begins to deepen
as it moves towards the Great Lakes Tuesday. Unlike the lead
shortwave which weakens with time, this feature is expected to
gradually strengthen and gain amplitude as it moves eastward into
Wednesday. Additionally, this shortwave will be joined by an
impressive jet streak to its south (reaching 160 kts from the
Central Plains to the Ohio Valley) and accompanied by Pacific
moisture (PWs above the 90th climatological percentile according to
NAEFS). The resulting surface low which will develop will
additionally enhance ascent, and a swath of moderate to heavy
precipitation is likely from the western Great Lakes through New
England.

Thermally, the environment is marginal for wintry precipitation due
to antecedent ridging aloft and strengthening WAA, so p-type from
WI, across the Great Lakes, and into at least central New England
will likely be a mix of rain, snow, sleet, and freezing rain. The
mixed precip will result in some impacts, but WSSI-P indicates only
minor impacts expected due to the progressive nature and mixed
p-type in this region. Still, WPC probabilities for ice accreting
to at least 0.1" reach 30-50% from near the Twin Cities through
central WI and into lower MI. Locally 0.2" of ice is possible, but
snow amounts are expected to be very light as the guidance has
trended a bit warmer tonight.

During D3, secondary low pressure development in the Gulf of Maine
could make snowfall and impacts a bit more impressive over New
England. While there remains considerable uncertainty into the
timing of this secondary low development, a surge of cold air
wrapping behind (and a developing in-situ CAD) should keep p-type
primarily snow in northern New England and mixed
snow/sleet/freezing rain in the higher elevations of Upstate NY and central/southern New England. This is reflected by an increase in
WPC snowfall probabilities, which, while still modest, are as high
as 10-30% D2 into D3 in the higher terrain of NH and ME. Icing to
the south of the snow may locally reach above 0.1" (30-50% chance
in the Adirondacks, Greens, and Monadnocks).


...California...
Day 1...

Amplifying trough off the Pacific Coast will deepen into a closed
low today, with this closed center drifting southeast towards Baja
California by Wednesday morning. Downstream of this evolution,
continued SW mid-level flow and aligned Pacific jet energy will
pump moisture northeast, reflected by high probabilities (>80%
chance) for IVT exceeding 250 kg/m/s surging into CA. Although this
IVT will be pushed onshore via WAA, snow levels will generally
remain around 5000 ft as the WAA is offset by slowly sinking
heights downstream of the trough axis. At the surface, of wave of
low pressure will drop along the CA coast, and while there is
considerable spread in the longitudinal placement of this feature,
sufficient additional ascent into the moistening column will
result in periods of heavy snow above 5000 ft in the Sierra and
northern CA ranges D1, and WPC probabilities are high (>90%) for at
least 6 inches more of snow, with more than 12 inches possible in
the higher terrain, especially around Mt. Shasta.


...Olympics, Cascades, and Northern/Central Rockies...
Days 2-3...

Mid-level flow becomes increasingly zonal across the Pacific,
directing energy and moisture into the Pacific Northwest beginning
on Tuesday. Aloft, a jet streak will intensify directly atop the
zonal mid-level flow, providing additional funneling of moisture
onshore before the jet starts to slowly sink southward on
Wednesday. This is reflected by a brief period of elevated IVT

90% chance exceeding 250 kg/m/s but less than 25% chance of 500

kg/m/s) Tuesday into OR/WA. As forcing for ascent increases D2 and
D3 through gradual height falls, left-exit diffluence, and
impressive upslope into the Olympics, Cascades, and Northern
Rockies, heavy snowfall will result in these areas, with snow
levels Tuesday 2000-3000 ft, falling to as low as 1000 ft late
Wednesday (higher but still just around 2500 ft in the Central
Rockies).

This cooling column, increasing ascent, and impressive moisture
indicates that heavy snowfall will become increasingly widespread
above these snow levels, especially in the upwind regions of the
Olympics, Cascades, and Northern Rockies. Forecast soundings
suggest steepening lapse rates up to as high as 750mb, which
indicates accumulating snow could occur even lower than these snow
levels, and the NBM 10th% fall to as low as 500 ft in the Pacific
Northwest, so lowland snow is possible late in the forecast period.
However, the most significant accumulations, which are likely to
be impressive, will be above 2000 ft, but will encompass most of
the Cascade and Northern Rockies Passes leading to challenging
travel later this week. WPC probabilities D2 for more than 6 inches
of snow are high (>70%) in the Olympics, Cascades of WA and OR,
the Northern Rockies, and as far south as the NW WY ranges (Tetons,
Wind Rivers), with 1-2 feet likely in the higher elevations of
these ranges. During D3, precip wanes a bit across the
Intermountain West, but persists in heavy fashion across the
Olympics and Cascades where WPC probabilities for 12+ inches remain
above 50%. As noted above, the falling snow levels will result in
dangerous travel across all of the important Cascades Passes this
week.



Weiss


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FOUS11 KWBC 051907
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
207 PM EST Mon Jan 5 2026

Valid 00Z Tue Jan 06 2026 - 00Z Fri Jan 09 2026


...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

A progressive shortwave trough over southern Ontario is producing
weak PVA over the Northeast, along with minor 850-700mb WAA ahead
of the trough. Sufficient 850-300mb moisture is present to support
periods of light-to-moderate snow over the Northeast this afternoon
and evening, but snow should taper off not long after midnight.
Minor snowfall accumulations of 1-4" are expected with some slick
conditions on untreated surfaces possible.

As the trough in the Northeast exits east into the North Atlantic
tonight, another disturbance with Pacific origins follows on its
heels as it develops a wave of low pressure in the Midwest. Located
beneath the divergent left-exit region of a 150kt 250mb jet streak,
the storm will gradually strengthen at the same time as 850-700mb
WAA ahead of the low also increases. While this disturbance is
similar to the one over the Northeast in that it is progressive,
there will be a stronger warm nose aloft that makes ice the primary
concern over the Midwest and Great Lakes this time around. An icy
wintry mix is beginning over parts of the eastern Dakotas and
central MN this afternoon, but as WAA increases, so will the rates
of sleet and freezing rain. Look for icy conditions to unfold
across WI and over MI's U.P. (Upper Peninsula) tonight, then over
MI's L.P. (Lower Peninsula) by Tuesday morning. The wintry mix may
linger over the Great Lakes and Midwest through midday Tuesday, but
should taper off by Tuesday evening, meaning there could still be
lingering icy conditions for the Tuesday afternoon rush hour. WPC
probabilities show at least moderate chances (>50%) for ice
accumulations over one-tenth of an inch of ice from southern MN to
northern MI. The WSSI shows a large swath of at least Minor
Impacts (slick travel conditions possible, use caution) from
southern MN on east through northern WI and into central MI. There
is an area denoting Moderate Impacts (hazardous travel conditions,
closures possible) in the heart of WI where localized ice
accumulations could approach one-quarter inch.

As the storm tracks over southern MI Tuesday afternoon, the same synoptically-forced mechanisms aloft will support periods of snow
over the Adirondacks and northern New England. Farther south, a
wintry mix of sleet and freezing rain will envelope central NY,
northern NJ, and northeast PA starting as early as Tuesday
afternoon, then advance east into the heart of New England with the
Green Berkshires, and Worcester Hills Tuesday night. Throwing a
wrench into the forecast is the expected development of a coastal
low along a coastal front off southern New England. This transition
from the primary low over southern Ontario to the new coastal low
off the MA Capes will be pivotal in how long central New England
stays a wintry mix and when/if they transition to snow. Northern
Maine and the White Mountains have the greater chances of seeing
snow as their primary precip type for this event Tuesday night and
into Wednesday morning. Through the daytime hours Wednesday, an icy
wintry mix is likely to linger over coastal ME but all
precipitation tapers off by Wednesday evening.

WPC probabilities show high chances (>70%) for ice accumulations

0.01" over the Catskills, Adirondacks, and much of interior New

England. The Adirondacks, Berkshires, Green, and Worcester Hills
have moderate chances (40-60%) for ice accumulations over one-tenth
of an inch. In terms of snowfall, the tallest peaks of the
Adirondacks, northern Greens, Whites, and northern ME show moderate
chances (40-60%) for snowfall over 2" through Wednesday evening,
but should the coastal low strengthen faster, localized snowfall
totals of 4-6" could transpire in northern ME. WSSI shows these
winter hazards generally look to cause Minor Impacts, indicating
the potential for some areas of hazardous travel due to snow and
ice Tuesday night and through Wednesday.


...Olympics, Cascades, and Northern/Central Rockies...
Days 2-3...

A powerful storm system over southern AK will work in tandem with
an unusually strong subtropical ridge north of HI to create a
robust 160kt 250mb jet streak in the northeast Pacific. This
enhanced polar jet will direct a potent IVT that ranges between
250-500 kg/m/s at the Pacific NW, while at the same time, being
co-located beneath the divergent left-exit region of the
aforementioned 250mb jet streak. While moisture content is not
overly anomalous, the westerly IVT supporting enhanced upslope
flow, falling mid-upper level heights, and supportive jet streak
dynamics will support rounds of heavy mountain snow over the
Cascades and Olympics. Snow levels will fall to as low as 2,000ft,
although the heavier and more impactful snow will be observed above
3,000ft. The heaviest snowfall arrives Tuesday afternoon, and
following a brief break in the heavier snowfall rates early
Wednesday morning, another disturbance arrives later in the day
with more snow in the Cascades and Olympics. This time, with a
colder air-mass aloft, snow levels dip to as low as 1,000ft
Wednesday afternoon and continuing into Thursday.

With snow continuously falling in these ranges through Thursday,
WPC's 72-hour snowfall probabilities are quite impressive with high
chances (>70%) for snowfall totals >24" above 3,000ft in the
Cascades and Olympics, including passes such as Snoqualmie and
Stevens. Current WSSI shows Moderate Impacts at these passes
(hazardous travel, potential closures) but given the higher end
snowfall potential, the WSSI-P does depict a scenario (20-30%
potential) for Major Impacts that would imply more dangerous travel
conditions. Regardless, multiple days of heavy snowfall is
expected, so passes will likely contend with prolonged delays and
potential closures.

The Pacific moisture spills east into the Northern Rockies as well
through the first half of the week. There is already lingering
Pacific moisture leftover from the heavy rainfall and mountain snow
in CA that is supporting periods of snow today and into tonight in
the Sawtooth, Bitterroots, Tetons, Wind River, and as far south as
the more remote reaches of the CO Rockies. As Pacific moisture
arrives Tuesday afternoon thanks to 250 kg/m/s IVT extending as far
east as eastern WA, periods of heavy snow ensue above 4,000ft in
the northern Bitterroots, above 5,000ft in the Lewis Range, Blue,
and Sawtooth Mountains, and above 7,000ft in the Absaroka, Tetons,
and Bear River Ranges. WPC probabilities over the next 72-hours
show high chances (>70%) for over 12" of snow in these ranges with
moderate chances (>50%) for snowfall eclipsing 24" in the more
remote elevations of the Bitterroots, Sawtooth, Tetons, and Wind
River ranges. The peaks of the Tetons sport the best odds of seeing
localized snowfall totals over 3 feet.

By Wednesday evening, attention turns to the central Rockies where
they will be placed ahead of two approaching shortwave troughs; one
diving south and east from the Pacific NW and another approaching
from northwest Mexico. As the former disturbance deepens Wednesday
night and into Thursday, periods of mountain snow are likely to
envelope the Wasatch, Uinta, all of the CO Rockies, and even as far
south as the Mogollon Rim and the Rockies of NM. Guidance shows a
fair amount of uncertainty in the handling of these two features,
so confidence in totals remains low. That said, the pattern support accumulating mountains snow (generally above 7,000ft) Wednesday
night and into Tuesday. Residents along the Front Range of the
CO/WY/NM Rockies will want to monitor the forecast closely as this
could result cause impacts to travel and commerce late week.


Mullinax





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