Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0349 AM CST Mon Dec 21 2020

Valid 241200Z - 291200Z

...DISCUSSION...
A deep and mature upper trough is expected to cover much of the
central and eastern CONUS early D4/Thursday. Primary low associated
with this system will likely be occluded over Ontario but secondary
cyclogenesis is anticipated over the Southeast, with the resulting
low then moving quickly northeastward along the lee of the
Appalachians into the northern Mid-Atlantic. Some severe potential
may develop ahead of this low and its attendant cold front as it
moves quickly eastward. However, differences within the guidance
regarding frontal timing as well as uncertainty regarding antecedent
moisture return currently limit predictability. 

High pressure will likely build across the central CONUS in the wake
of the upper trough on D5/Friday and across the eastern CONUS on
D6/Saturday. A shortwave is currently expected to move across the
Intermountain West on D6/Saturday and across the Plains D7/Sunday.
Moisture return ahead of this system will likely remain confined to
central/east TX and the Lower MS Valley. Instability will be limited
even within this corridor of return flow and severe potential
currently appears very limited.

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