ACUS01 KWNS 151958
SWODY1
SPC AC 151957

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0257 PM CDT Thu Oct 15 2026

Valid 152000Z - 161200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDWEST...

...SUMMARY...
Thunderstorms capable of severe wind gusts and a tornado or two are
possible today across parts of the middle Mississippi and Ohio
Valleys.

...20z Update...
A loosely organized cluster of storms has developed over southeast
Illinois, positioned on the northern periphery of modest instability
(MLCAPE near 1000 J/kg) that has developed where skies have remained
at least partially clear. Although persistent cloud cover has thus
far limited destabilization of the downstream environment, low-level
warm/moist air advection combined with some breaks in cloud cover
may promote further destabilization. Should this occur, ample
deep-layer shear of 40-45 kts should help to maintain convective
organization, with a few damaging wind gusts possible. Therefore, a
Slight Risk has been maintained, but trimmed to areas in/downstream
of the ongoing convective activity. 

In addition, a minor expansion of the wind/tornado probabilities was
made, extending into portions of far southern Illinois and far
southwest Indiana where visible satellite indicates some cumulus
development amid the aforementioned area of instability. A few
isolated damaging wind gusts would be possible if isolated cells are
able to develop in this region.

Elsewhere, a few damaging wind gusts are possible this
afternoon/evening across portions of northwest Texas. See MCD #2378
for additional details.

..Karstens.. 10/15/2026

.PREV DISCUSSION... /ISSUED 1155 AM CDT Thu Oct 15 2026/

...Midwest/Ohio Valley...
Extreme/record-caliber seasonal moisture content exists over the
region with warm-sector prevalent 2+ inch Precipitable Water values
and surface dewpoints in excess of 70F. A surface wave over the
middle part of Missouri late this morning should gradually/modestly
deepen as it progresses east-northeastward near a northward-shifting
warm front, although the front/warm sector are a bit muddled by
ongoing convection across southern portions of Missouri and
Illinois. 

Current split flow over the Great Plains will quickly resolve, with
a central Plains shortwave trough/speed max phasing with a
broader-scale upper trough over the Upper Midwest through tonight.
The net result will be a strengthening of deep-layer winds
along/north of the warm sector that will shift poleward, although to
what exact degree/spatial extent is uncertain given some of the
ongoing convection.

At least some scattering of warm-sector cloud cover, diurnal heating
and the increasing moisture content with northward extent will allow
for modest cool season destabilization, with SBCAPE potentially
exceeding 1000 J/kg across the lower Wabash Valley and
southern/downstate portions of Illinois and Indiana. This should
allow for re-development/intensification of storms this afternoon,
although the exact magnitude of today's severe risk is still a bit
uncertain and contingent on surface heating/destabilization. But
this scenario could include a few supercells, with the possibility
of a semi-focused severe/some tornado risk near the warm front,
which may be augmented by some of the prior convection, and ahead of
the surface low. Supercells aside, some semi-organized clusters
capable of wind damage should evolve within the high-moisture
content environment and 40+ kt effective shear. Overall storm
intensity is likely to wane within a couple hours of sunset,
generally by late evening.

...North/West Texas...
An outflow-augmented cold front will continue to spread
southeastward. The tendency for post-frontal convection should
remain the dominant scenario with boundary-parallel deep-layer flow
contributingto a more anafrontal character. Gradual diurnal heating
could support some intensification of storms along the leading edge
of the composite boundary this afternoon. As such, some stronger
wind gusts are plausible, but this scenario and related potential
for organized severe storms is currently expected to remain limited.

$$