SPC AC 200538
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Wed Oct 20 2021
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
OHIO INTO WESTERN PENNSYLVANIA AND FAR WESTERN NEW YORK AS WELL AS
A few showers/thunderstorms with gusty winds will be possible from
eastern Ohio into western Pennsylvania Thursday afternoon. Isolated
thunderstorms capable of marginally severe hail might occur late
Thursday night over southern Oklahoma.
...Eastern Ohio and western Pennsylvania...
Limited low-level moisture with a narrow corridor of mid 50s F
dewpoints will return through the pre-frontal warm sector from OH
into western PA. Forcing for ascent accompanying a progressive
shortwave trough and its attendant cold front will move through the
OH Valley during the day. Low-topped convection is expected to
develop within the narrow corridor of very weak instability (less
than 400 J/kg MUCAPE) along and just ahead of the front. Activity
will be embedded within strong unidirectional southwesterly winds.
Some potential will exist for higher momentum air to be transported
to the surface within some of the rain cores. However, any severe
threat should remain limited by the very marginal thermodynamic
A cold front is expected to stall in vicinity of the OK/TX border.
Partially modified Gulf air will return northward beneath 6.5 - 7
C/km mid-level lapse rates, resulting in up to 1000 J/kg MUCAPE from
northwest TX into southern OK overnight. Some uncertainty exists
regarding extent of thunderstorm initiation, but modest isentropic
ascent north of this boundary might contribute to the development of
a few thunderstorms very late in the period, and some of these
updrafts might become capable of producing a few instances of
marginally severe hail.
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z