SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1216 AM CDT Sun Oct 25 2020

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible across the U.S.
Sunday through Sunday night.

...FL to the Carolina/Virginia Coastal Vicinity...

An upper shortwave trough will be advancing northeastward early in
the period while a cold front drops southward to the lee of the
Appalachians across the Piedmont. Meanwhile, the southern extent of
the front across FL will become increasingly diffuse over the
Peninsula. Moist southerly low-level flow ahead of these features
amid weak instability and modest forcing for ascent should result in
isolated thunderstorms through the afternoon.

...Four Corners into the Southern Great Plains Vicinity...

A series of shortwave troughs will dig southward across the western
U.S. and across the northern Plains on Sunday, bringing a belt of
strong southwesterly mid/upper level flow from the southwestern U.S.
northeastward across the Plains. As an intense surface high builds
over the northern Rockies and adjacent High Plains, a strong cold
front will surge southward across the central and southern Plains. A
somewhat shallow intrusion of seasonably cold air will surge
southward behind the front, while southerly low/mid level flow
maintains moist advection aloft. Isolated elevated thunderstorm
activity appears likely during the evening and overnight in this
warm advection regime, atop the shallow cold layer in the vicinity
of the midlevel baroclinic zone, from parts of western TX through OK
and into parts of the Ozarks.

Further west across the Great Basin, forcing for ascent will
increase over the Four Corners vicinity as the upper trough digs
southward across the western Great Basin. As this occurs, cooling
aloft will result in steepening lapse rates amid modest midlevel
moisture. This should result in weak, but adequate instability for
isolated thunderstorm development Sunday afternoon and evening
across the Four Corners vicinity.

..Leitman.. 10/25/2020

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