ACUS02 KWNS 181732
SWODY2
SPC AC 181730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Thu Sep 18 2025
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR SOUTHWEST NE
INTO WESTERN/CENTRAL KS...
...SUMMARY...
Isolated severe storms are possible across parts of the central
Plains on Friday. Isolated strong storms may also occur across parts
of the Southwest and from the ArkLaTex into the Upper Midwest.
...Synopsis...
A broad mid/upper-level trough will remain in place across parts of
the northern/central Plains and Upper Midwest on Friday. Multiple
embedded vorticity maxima will move traverse the larger-scale trough
through the period. Across the West, a midlevel shortwave trough
will move across parts of central/northern CA/NV, while a deeper mid/upper-level trough offshore of southern CA will move slowly
eastward.
...KS/southern NE vicinity...
A somewhat conditional Marginal Risk has been added from southwest
NE into western KS, due to the potential for isolated supercells
within a northwest-flow regime.
Guidance has generally trended toward a more vigorous midlevel
shortwave trough and jet maximum moving southeastward from the
northern High Plains toward the lower MO Valley through the period.
In response to this system, a weak surface low is forecast to
develop across the central High Plains. Guidance continues to vary
somewhat regarding the placement of any surface boundaries and
extent of low-level moisture return during the day, but at least
isolated storm development will be possible by late afternoon from
southern NE into northwest KS.
Deep-layer shear will become favorable for organized convection
within the northwesterly flow regime along the southwest periphery
of the aforementioned shortwave trough. Buoyancy may remain
relatively modest (with MLCAPE of 500-1500 J/kg), but recent CAM
guidance depicts potential for isolated supercell development, which
could pose a threat for localized hail and gusty winds. A more
uncertain scenario is for convection directly associated with the
shortwave trough to intensify as it approaches southeast NE, but
there is considerable uncertainty regarding diurnal destabilization
in this area.
A strengthening low-level jet could support some storm clustering
and maintenance of elevated convection into late Friday night across
parts of KS. Longevity of the severe threat into Friday night is
uncertain, but isolated hail and strong gusts cannot be ruled out
within this nocturnal regime as well.
...Upper Midwest...
A midlevel shortwave trough initially over parts of IA/MO is
generally forecast to move north-northeastward toward MN/WI through
the day, as the trailing shortwave moves into the central
Plains/lower MO Valley. Scattered to numerous storms will be
possible across parts of the Upper Midwest/MS Valley, within a
relatively moist and uncapped environment. Midlevel lapse rates and
deep-layer shear are generally forecast to remain rather weak, so
any severe threat will likely be dependent on sufficient diurnal heating/destabilization. Confidence in a mesoscale corridor of
organized severe threat is too low for probabilities at this time,
but a few strong storms will be possible.
...ArkLaTex into the lower/mid MS Valley...
Scattered storm development will be possible during the afternoon
from the ArkLaTex into the lower/mid MS Valley, though details
regarding heating/destabilization are somewhat uncertain, due to the
potential impact of upstream morning convection and related cloud
debris. While deep-layer flow/shear will generally be weak across
the region, a few strong storms will be possible if sufficient
heating occurs. Severe probabilities may eventually be needed if
confidence increases regarding stronger diurnal destabilization.
...Southwest...
Scattered to widespread storms will again be possible across parts
of the Southwest on Friday, within a relatively moist and moderately
unstable environment. Deep-layer shear will generally be modest,
resulting in uncertainty regarding any organized severe potential.
However, localized strong gusts and small to near-severe hail will
be possible with the strongest storms.
..Dean.. 09/18/2025
$$
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