SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1127 PM CST Tue Nov 24 2020

Valid 251200Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
OHIO VALLEY TO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms are possible today from the
lower Mississippi Valley to the lower Ohio Valley. Locally damaging
winds should be the main threat, although a tornado or two could
also occur.

...Lower Ohio to Lower Mississippi Valley...

Strong mid-level vort/upper low centered along the KS/OK border will
progress into eastern MO by 18z before ejecting into OH by the end
of the period. Latest model guidance suggests the associated surface
low will advance to near STL by mid day and an arcing corridor of
enhanced boundary-layer heating is expected ahead of the front. It
appears surface temperatures should warm into the lower 60s as far
north as southern IL/IN which would yield upwards of 800-900 J/kg of
SBCAPE where dew points should be in the mid-upper 50s. Forecast
soundings suggest isolated thunderstorms will likely develop ahead
of the upper low by 17-18z within a strongly sheared environment
that would favor organized updrafts. This activity would
spread/develop east during the afternoon, possibly developing in an
arcing fashion across western KY into middle TN. Locally damaging
winds are the primary risk, but some tornado threat does appear
possible. At this time will maintain MRGL Risk due to low confidence
in storm coverage; however, this region will be monitored for higher
severe probabilities if confidence in organized severe increases.

Farther south, band of frontal convection is currently noted across
east TX. This activity should progress into the lower MS Valley by
sunrise. With the primary forcing expected to spread across the
OH/TN Valley region, convection along the trailing front may not be
that organized and will be less sheared than convection farther
north. Even so, locally damaging winds may be noted with the
strongest storms.

..Darrow/Squitieri.. 11/25/2020

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