AWUS01 KWNH 151842
FFGMPD
FLZ000-160000-

Mesoscale Precipitation Discussion 0063
NWS Weather Prediction Center College Park MD
240 PM EDT Sun Mar 15 2026

Areas affected...South FL

Concerning...Heavy rainfall...Flash flooding possible

Valid 151840Z - 160000Z

SUMMARY...Slow-moving clusters of showers and thunderstorms with
extreme rainfall rates may cause flash flooding going through
early this evening. This could include some urban impacts.

DISCUSSION...The latest GOES-E IR satellite imagery along with
radar shows slow-moving clusters of very heavy showers and
thunderstorms impacting portions of Miami-Dade and Collier
Counties.

This convection is focusing within a moist and unstable
environment characterized by MLCAPE values of 1500 to 2500 J/kg
and PWs of 1.5 to 1.7 inches. Some modest shear is in place with
as much as 20 to 30 kts of effective bulk shear. Much of the
activity recently though is tending to get its focus along the
presence of multiple mesoscale boundaries including outflow and
sea-breeze boundaries where there is small-scale convergence
working with the favorable thermodynamic environment.

Some modestly divergent flow aloft is noted also given proximity
of a weak shortwave west of the FL Straits and Cuba. This modest
deep layer ascent coupled with colliding surface boundaries should
tend to keep the convective threat maintained going into the
evening hours before sufficient levels of instability exhaustion
occurs to promote a weakening trend of the convection.

Already parts of the FL Everglades in Miami-Dade County have seen
over 5 inches of rain, with much of the activity staying away from
the urban areas. However, over the next few hours there will still
be a threat locally for some of these stronger thunderstorms and
heavier rainfall rates to impact the more populated areas of
southern FL which in this case will extend to the the southwest
coast including areas from Ft. Myers down through Naples. The
southeast coast of FL meanwhile from Miami down to Homestead will
still need to closely watch some of these slow-moving cells.

Rainfall rates of 2 to 4 inches/hour and storm totals locally
exceeding 5 inches are expected where any cells become anchored.
Earlier runs of the HRRR and RRFS were suggesting this near parts
of southwest FL in particular. As such, some areas of flash
flooding will be possible given the very high rainfall rates and
totals which may include some urban impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6VYKq4ZHl918Q3pvMYHNoqpOeYvAl-jH0wrrSGBnRCSi1o3jC2LsBNc7NHfFUTvg-7RE= -pJF1ZBRxkXB7uyLw6uPMHo$ for graphic product...

ATTN...WFO...KEY...MFL...TBW...

ATTN...RFC...ALR...NWC...

LAT...LON 27018174 26468098 26118014 25657992 25178031=20
25298104 26088186 26738218=20

=3D =3D =3D
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AWUS01 KWNH 262047
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-270230-

Mesoscale Precipitation Discussion 0064
NWS Weather Prediction Center College Park MD
446 PM EDT Thu Mar 26 2026

Areas affected...Northern Ohio...Western & Central PA... Southwest
NY...

Concerning...Heavy rainfall...Flash flooding possible

Valid 262045Z - 270230Z

SUMMARY...Saturated upper-layer soils/low FFG may be locally
exceeded given potential for quick burst thunderstorms capable of
.5-.75"/hr rates and localized totals of 1.5-2", especially
in/near corridor or two of repeating cells.

DISCUSSION...A strong 150-180kt 250mb zonal jet is streaking
across the northern Great Lakes into southern Quebec with a subtle
but sufficiently diffluent right exit region across the Lower
Great Lakes this afternoon. In response, strong southwesterly
warm-air advection regime is drawing higher moisture and slightly
above normal higher theta-E air across the northern Ohio Valley
into the Allegheny Plateau. Low level flow is solid per VWP with
35-45kts of 925-850mb flow from the southwest with sufficient
veering through 700-500mb to allow for a fairly unidirectional
steering flow, with allowable for upstream redeveloping cells to
potentially repeat across the area of concern late this afternoon
into evening.=20

At the surface a well defined front extends from the main surface
low in SE IA across the southern LP of Michigan where secondary
weaker wave exists, likely responding to the mid-level
shortwave/diffluence pattern aloft. Surface moisture convergence
in proximity to the surface front is further enhanced by cooler
Lake Breeze and sharper low level temperature gradient along the
southern coasts. This isentropic boundary in the low level flow
regime will support enhanced moisture convergence at the
northwestern nose of the mid-level instability pool upstream over
IL/IN/NW OH. Available moisture is slightly above average with
total Pwat values AoA 1.25", though the bulk is below 700mb and
any thunderstorm development will help to load in the lower
profiles providing some increased rainfall potential. Forward
propagation will be very fast limiting overall duration, but
Hi-Res CAMs include recent WoFS runs suggest isolated but broader
updrafts capable of the very quick bursts of .5-.75" in 15-30 minutes...particularly further west and deeper into the more
unstable (1500+ J/kg MUCAPE), higher moisture.=20

However, the hydrological ground conditions are very sensitive as
green-up is just about to start. FFG values are below average
with hourly values about 1" reducing to .5-.75" across northern PA
into S central PA. NASA SPoRT LIS products show 0-40cm saturation
values over 60% increasing to over 80% where the lowest FFG value
are; so even less vertically intense showers/thunderstorms capable
of .25-.5"/hr rates downstream into NY/Central PA are likely to
shed nearly all rain toward runoff. The overall magnitudes and
coverage are likely to be limited in scope and lower end, but
still pose a possible incident or two of flash flooding. This is
also a concern across the larger urban centers of NE OH toward
Pittsburgh metro later this evening.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9JCEIU5YItr7GdI7YePu8DnzptH-WUp77K6dlDwxPSN7BGp-1c-UvyeeyqpzQ03SeznQ= 4fb5sFTjjRsN87RHTbZVBP8$ for graphic product...

ATTN...WFO...BGM...BUF...CLE...CTP...ILN...IWX...PBZ...

ATTN...RFC...RHA...TAR...TIR...NWC...

LAT...LON 42667650 42057570 41177590 40477698 40127924=20
40008191 39968419 40858437 41558200 42068053=20
42287976 42627812=20

=3D =3D =3D
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