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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