352
ACUS02 KWNS 300443
SWODY2
SPC AC 300442

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1142 PM CDT Mon Sep 29 2025

Valid 011200Z - 021200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible Wednesday
through Wednesday night.

...Discussion...
Beneath a confluent mid-level regime, in the wake of a short wave
trough digging off the north Atlantic coast, it still appears that
the center of an expansive cool surface ridge will shift southeast
of the southern Hudson/James Bay vicinity through much of the
Northeast and Mid Atlantic by late Wednesday night.  The weaker
southwestern flank of this ridge may be maintained as far south and
west as the northern Gulf Basin and southern Great Plains, with the
frontal zone on the leading edge of the cooler air stalling across
or just south of the southern Florida Peninsula, while advancing
further offshore of the remainder of the Atlantic Seaboard, in the
wake of east-northeastward accelerating Humberto and Imelda.

Upstream flow westward into the northern mid-latitude Pacific may
continue to trend a bit more zonal through at least this period.
Within this regime, an initially deep, occluded surface cyclone
offshore of the southern British Columbia/Pacific Northwest coast is
forecast to undergo rapid weakening near Vancouver Island.  However,
mid-level troughing, with a couple of notable embedded
perturbations, is forecast to gradually progress into/across the
Pacific coast by 12Z Thursday.

...Northwest...
As a modest residual mid-level cold pool migrates inland off the
northeastern Pacific, it may contribute to sufficient boundary-layer
destabilization for scattered weak thunderstorm activity west of the
Cascades, and perhaps farther inland across parts of the northern
intermountain region, Wednesday through Wednesday night.

...Great Plains...
Models indicate sufficiently steep lapse rates and
boundary-layer/mid-level moisture to support weak to moderate
potential instability focused near modest surface troughing across
the northern into central Great Plains.  As stronger mid/upper
support for ascent generally shifts north of the international
border early in the period, weak lift and warm mid-level
temperatures may inhibit thunderstorm development rooted within a
narrow corridor of boundary-layer instability forecast across the
eastern Dakotas by late afternoon.

Potential for convection rooted within moistening layers aloft
remains more unclear, and latest guidance suggests that isolated
convection capable of producing lightning might be possible across a
sizable portion of the northern and central Great Plains.  However,
it still appears probable that this will be rather sparse in
coverage, with less than 10 percent thunderstorm probabilities
maintained.  One exception may be across the Red River/northwestern
Minnesota vicinity, where a clustering of weak thunderstorms appears
possible supported by lift associated with low-level warm advection,
particularly early in the period.

...Florida Peninsula...
Low-level convergence aided by moist post-frontal northeasterly to
easterly low-level flow may support isolated to widely scattered
thunderstorm development near the Atlantic coast during the day.
Additional development inland across the peninsula Wednesday night
is more unclear, but could be aided by mid-level cooling associated
with a weak approaching mid-level trough.

..Kerr.. 09/30/2025

$$