408
ACUS01 KWNS 181238
SWODY1
SPC AC 181236

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0636 AM CST Tue Nov 18 2025

Valid 181300Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE LOWER OHIO VALLEY...

...SUMMARY...
Isolated strong to severe storms are possible across parts of the
lower Ohio Valley region today.

...Mid Mississippi/Lower Ohio Valley...
Elevated thunderstorms ongoing this morning across the mid MS/lower
OH Valley are being aided by a southwesterly low-level jet and
related warm/moist advection. This activity may pose an isolated
hail threat as it tracks eastward this morning across the lower OH
Valley before eventually encountering a less unstable airmass. A
mid-level shortwave trough will advance eastward across the
Midwest/mid MS Valley into the OH Valley through this evening. A
weak surface low attendant to this shortwave trough will likewise
develop east-southeastward across MO into the lower OH Valley while
gradually weakening. Low-level moisture will return northward across
this region ahead of a east-southeastward advancing cold front.

Current expectations are for some re-intensification of convection
to occur this afternoon across the southern IL/western KY vicinity
as strong ascent associated with the shortwave trough overspreads
this region. There is still some uncertainty with how far north the
surface warm sector will be able to advance, and daytime heating may
be muted by persistent cloudiness. But, the best combination of weak
to locally moderate instability and favorable deep-layer shear
should overlap across the mid MS/lower OH Valley this afternoon and
evening as a 50-60+ kt westerly mid-level jet moves across these
areas. Any sustained supercell may be capable of producing severe
hail along with locally damaging winds, with elevated convection
possible north of the warm front into central IL/southern IN. Some
threat for a tornado or two may also exist if sufficient
boundary-layer instability can advance far enough northward in
tandem with the warm front and enhanced low-level shear to support
surface-based thunderstorms. No changes have been made to the
Marginal Risk with this update. Confidence in a more concentrated
corridor of severe risk was not high enough to include greater
severe probabilities at this time, but trends will be monitored.

...Lower Colorado River Valley/Arizona...
A closed mid/upper-level low along the coast of central/southern CA
will make only slow progress southward today. Large-scale ascent
associated with a south-southwesterly mid-level jet should encourage
convective development today across parts of the lower CO River
Valley and AZ. While deep-layer shear appears adequate for organized
updrafts, weak instability will likely limit the overall severe
threat across this region.

..Gleason/Broyles.. 11/18/2025

$$