ACUS01 KWNS 120525
SWODY1
SPC AC 120524

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 AM CDT Sat Sep 12 2026

Valid 121200Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL AND SOUTHERN PLAINS...OZARK PLATEAU...AND UPPER OHIO
VALLEY...

...SUMMARY...
Widely scattered severe storms capable of large hail up to two
inches and damaging wind gusts appear possible over portions of the
central and southern Plains into the Ozark Plateau on Saturday into
Saturday night. Isolated occurrences of damaging wind gusts may also
occur over portions of the upper Ohio Valley Saturday afternoon.

...Synopsis...

A belt of enhanced mid/upper-level flow will persist over the
north-central U.S., downstream from a vigorous upper low moving into
the Pacific Northwest. Meanwhile, a lower-latitude trough over the
lower OH and lower MS Valleys Saturday morning is forecast to weaken
while progressing through the OH and TN Valleys. At the surface, a
cold front will advance through the upper Great Lakes with the
trailing extension of the boundary pushing south through the lower
MO Valley and central Plains before linking with a surface low over
the southern High Plains.


...Central and Southern Plains into the Ozark Plateau...

Persistent capping across the pre-frontal warm sector and generally
weak forcing for ascent lead to considerable uncertainty in
thunderstorm evolution through the forecast period. A number of the
00Z models (both convection-allowing and parameterized) indicate
areas of thunderstorms ongoing at 12Z Saturday over the central
Plains within a zone of modest warm advection and moisture transport
associated with a weakening low-level jet. One possible scenario is
for the continued southeast movement of the early-day storms through
eastern KS and southwest MO into portions of OK and AR by afternoon,
where a hot and moderate to strongly unstable air mass (i.e., MLCAPE
up to 2000-3000 J/kg) is forecast to develop. The instability
combined with around 30 kt of deep-layer shear would support
organized cold pool development in that scenario with an associated
risk for damaging wind gusts and large hail.

Renewed storm development appears possible from late morning into
afternoon from north of the front in south-central and southeast NE
to along or ahead of the front in northeast KS. Up to 40 kt of
deep-layer shear will coincide with the northern extension of the
stronger instability mentioned above to support supercell storm
modes with an associated risk for large hail up to two inches and
damaging wind gusts.  

A separate thunderstorm regime may also evolve by mid to late
afternoon over the eastern OK and TX Panhandles into western OK in
the vicinity of the surface low and southward-sagging front.
Forecast soundings indicate a deep, well-mixed boundary layer, which
will be supportive of a few severe wind gusts and isolated large
hail.

Confidence in any of the above scenarios/regimes remains too low to
include Slight Risk wind and hail probabilities with this forecast.
A categorical upgrade is possible in subsequent Day 1 outlooks once
finer-scale details become more clear.


...Upper Ohio Valley...

A spatially narrow corridor of stronger heating and resultant
instability (MLCAPE up to 1500-2000 J/kg) is forecast to develop
during the afternoon between denser clouds and precipitation to the
west, and a backdoor front/stationary boundary to the east.
Thunderstorms are expected to increase in coverage and intensity
through the afternoon within the instability axis, aided by
increased forcing for ascent associated with the approaching
mid-level trough. While mid-level lapse rates are expected to remain
relatively weak, deep-layer shear increasing to 30-35 kt coupled
with steepening low-level lapse rates suggests the potential for
some storm organization with the primary hazard being damaging wind
gusts. Backed low-level winds in the vicinity of the surface front
will boost low-level shear slightly and a brief tornado cannot be
ruled out as mature storms approach the frontal zone from the west.

..Mead/Halbert.. 09/12/2026

$$
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