Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1216 AM CDT Sat Sep 20 2025
Valid 201200Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO EVENING ACROSS PARTS OF THE SOUTH CENTRAL GREAT
PLAINS...
...SUMMARY...
Scattered strong thunderstorms may impact parts of the south central
Great Plains late this afternoon and evening, accompanied by some
risk for locally strong to severe wind gusts and perhaps some
marginally severe hail.
...Discussion...
In the northern mid-latitudes, flow across the Pacific appears
likely to remain strong and zonal, with one significant short wave
trough on the leading edge of this regime forecast to progress
inland of the British Columbia and portions of Pacific Northwest
coastal areas during this period. Downstream, models indicate that
flow will remain more amplified across Canada into the northern
Atlantic, with one significant trough and embedded cyclone slowly
progressing offshore into the Labrador Sea/northwestern Atlantic
vicinity. In the wake of this feature, the center of cool surface
ridging is forecast shift from western Quebec into New England, with
a ridge axis building south-southwestward to the lee of the
Appalachians through much of the Atlantic Seaboard.
In advance of the trough migrating inland of the Pacific, modest
deepening of surface troughing appears possible as far south as the
lee of the northern U.S. Rockies. However, much of the U.S. and
adjacent interior southern Canada will generally remain under the
influence of a weak split flow including larger-scale troughing in
one branch across the northern Great Plains into Great Lakes/Ohio
Valley, and troughing across the southern mid-/subtropical latitudes
of the eastern Pacific and across the Southeast, within another
branch.
...South Central Great Plains...
Near the southwestern flank of the broad mid/upper troughing roughly
centered across the mid/upper Mississippi Valley, it appears that
boundary-layer destabilization may become characterized by
moderately large CAPE in a pre-frontal corridor centered across the
Texas Panhandle through northern Oklahoma by late this afternoon.
As this maximizes, it appears that low-level convergence near
modestly deepening surface troughing will support that initiation of
scattered thunderstorm activity, perhaps aided by forcing for ascent
associated with a subtle digging short wave perturbation. Although
deep-layer wind fields and shear are forecast to be generally weak,
forecast soundings characterized by relatively steep low-level lapse
rates, including modestly deep boundary-layer mixing, appear
conducive to localized strong to severe gusts and perhaps some
marginally severe hail with stronger cells into early to mid
evening.
..Kerr/Halbert.. 09/20/2025
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