Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0738 AM CDT Sat Sep 20 2025
Valid 201300Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTH-CENTRAL PLAINS...
...SUMMARY...
Scattered strong to locally severe thunderstorms may impact parts of
the south-central Plains this afternoon and evening, accompanied by
an isolated threat for strong to severe wind gusts and marginally
severe hail.
...South-Central Plains...
A small cluster of thunderstorms across northeast OK, southwest MO,
and northwest AR this morning has remained mostly sub-severe
overnight owing to weak instability and deep-layer shear. Current
expectations are for this activity to further weaken as it spreads
eastward across AR and southern MO through mid/late morning. Outflow
from these thunderstorms has surged southward across much of OK per
radar imagery. Recent surface observations also show the primary
front arcs from the OK Panhandle vicinity northeastward into
central/eastern KS. A moist and moderately unstable airmass is
forecast to exist this afternoon along/south of the front where
daytime heating occurs.
Large-scale ascent aloft will remain nebulous/weak, with multiple
low-amplitude mid-level perturbations present on the eastern
periphery of upper ridging centered over Mexico and the Southwest.
Still, isolated to scattered thunderstorms should develop this
afternoon and evening, potentially along and south of the residual
outflow boundary from the ongoing convection this morning. As
low-level lapse rates become steepened through the day, isolated
strong to severe gusts may occur with the more robust thunderstorms
that form. Even though deep-layer shear will remain meager, modestly
steepened mid-level lapse rates and cool temperatures aloft may also
support occasional hail. The Marginal Risk has been adjusted for the
latest guidance and observational trends, with somewhat greater
confidence in convection occurring across the OK/TX Panhandles into
OK along/near the outflow boundary compared to locations farther
north in KS along the front.
...Upper Midwest/Great Lakes...
A weak upper trough over the Upper Midwest this morning will
translate slowly eastward across parts of the OH Valley and Upper
Great Lakes through the period. A seasonably moist low-level airmass
will remain over these areas along/south of a front, but mid-level
lapse rates are expected to remain quite poor. Ongoing precipitation
and cloud cover should also temper destabilization to some degree
through this afternoon, with only weak MLCAPE forecast to develop.
While isolated strong/gusty winds and small hail may occur with any
of the stronger cores that can form later this afternoon across
parts of WI into northern IL/IN and southern Lower MI, the overall
severe threat appears too limited to include low severe
probabilities at this time.
..Gleason/Grams.. 09/20/2025
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