Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 AM CDT Thu Sep 04 2025
Valid 041630Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NEW YORK INTO THE MID-ATLANTIC AND TENNESSEE VALLEY...AND PORTIONS
OF THE MID MISSOURI VALLEY...
...SUMMARY...
Isolated damaging winds may occur across parts of New York to the
Mid-Atlantic and Tennessee Valley this afternoon. Isolated severe
gusts are also possible across parts of the mid Missouri Valley late
this afternoon and early evening.
...New York into the Mid-Atlantic and Tennessee Valley...
A closed mid/upper-level low will remain centered over Ontario
today. Multiple mid-level perturbations will rotate around this
feature through the period, including a shortwave trough forecast to
advance generally east-northeastward across parts of the central
Appalachians/Mid-Atlantic into the Northeast. Showers and
thunderstorms are ongoing mainly ahead of a surface cold front from
parts of western NY southward to the TN Valley in a low/mid-level
moisture plume. Generally clear skies ahead of this activity should
allow for ample daytime heating of a modestly moistened low-level
airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO
show rather poor mid-level lapse rates, which will likely hinder
updraft strength even as weak instability develops this afternoon
with continued diurnal heating.
Modestly enhanced southwesterly low/mid-level flow should still aid
in some thunderstorm organization even with the apparent
thermodynamic limitations, with multicells the dominant convective
mode. Wherever low-level lapse rates can become steepened, a risk
for at least isolated damaging winds remains apparent. Some hail may
also occur with the strongest cores across parts of the TN
Valley/southern Appalachians where locally greater instability
should be present this afternoon. The Marginal Risk has been
adjusted for ongoing trends, but the potential for a more focused
corridor of scattered severe/damaging winds remains unclear.
...Mid Missouri Valley...
A mid-level shortwave trough and attendant strong speed maximum will
move quickly southeastward today from central Canada and the
northern Plains towards the mid MO Valley and vicinity. Pronounced
ascent associated with this jet should encourage convection to
develop by late this afternoon across parts of eastern SD and
vicinity. While low-level moisture and MLCAPE are both expected to
remain very limited, enhanced low/mid-level northwesterly flow may
still support some risk for severe gusts with any low-topped
convection that can develop and spread quickly southeastward before
weakening this evening with the loss of daytime heating.
...Kansas...
A sharp cold front will sweep southward across the central Plains
tonight. Elevated convection should form to the cool side of this
boundary late tonight through early Friday morning given sufficient
MUCAPE. Locally strong surface gusts and small hail may accompany
this activity amid robust low-level northerlies, but the overall
severe potential should remain fairly low given the tendency for
convection to be mostly elevated.
...Arizona/Lower Colorado River Valley...
Thunderstorms should develop again today across parts of
central/southern AZ and the lower CO River Valley, beneath weak
mid-level flow and on the periphery of increasing mid-level moisture
associated with Tropical Storm Lorena. Weak shear should keep
thunderstorms mostly disorganized, but occasional strong/gusty winds
may occur where low-level lapse rates can become steepened.
..Gleason/Lyons.. 09/04/2025
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