SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CST Mon Nov 23 2020 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE LOWER/MID MISSISSIPPI VALLEY...TENNESSEE VALLEY...AND SOUTHEAST... ...SUMMARY... Isolated strong to severe thunderstorms may occur Wednesday across parts of the lower/mid Mississippi Valley into the Tennessee Valley and Southeast. ...Lower/Mid Mississippi Valley into the Tennessee Valley and Southeast... A closed upper low with associated southwesterly mid-level jet should continue to advance from the lower/mid MS Valley to the Mid-Atlantic vicinity on Wednesday. A surface low initially over northern MO is forecast to develop northeastward across the Midwest/OH Valley and lower Great Lakes while slowly filling through the period. A cold front extending southward from this low should progress generally eastward across parts of the lower/mid MS Valley, TN Valley, and Southeast through the day. A broken line of showers/storms may be ongoing at the start of the period across these regions along/ahead of the cold front with a isolated/marginal severe threat. Substantial low-level moisture return will probably make only a limited northward advance ahead of the front. Still, diurnal heating and cooling mid-level temperatures with the approach of the upper trough/low may promote weak instability through Wednesday evening across the narrow warm sector. Given strong flow aloft attendant to the previously mentioned mid-level jet, there should be more than enough deep-layer shear to support organized storms. Isolated strong to damaging winds appear to be the main threat with any storms that can either persist along the front or develop ahead of it. A brief tornado or two also cannot be ruled out mainly early in the period, before low-level winds veer more west-southwesterly as the primary low-level jet shifts north of the surface warm sector and into the OH Valley by Wednesday evening. Eventually, the cold front should outpace the modest low-level moisture return across the TN Valley and Southeast, with a gradual reduction in the already isolated/marginal severe threat by late Wednesday evening as the system occludes. ..Gleason.. 11/23/2020
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