SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1156 PM CST Tue Jan 05 2021 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER FAR SOUTHERN MISSISSIPPI AND ALABAMA...AND THE FLORIDA PANHANDLE... ...SUMMARY... Thunderstorms are possible Thursday across the Southeast, with a conditional threat of isolated severe storms from the Mississippi and Alabama coasts into the Florida Panhandle. ...Synopsis... A strong shortwave trough with cyclonically curved jet max will move east across the southeastern states on Thursday, with upper low moving from northern LA toward the southern Appalachians by Friday morning. Of particular note will be the cold temperatures aloft, with -20 C at 500 mb as far south as Mobile AL. Strong westerly winds aloft will lengthen hodographs across the region, particularly the northern Gulf Coast. At the surface, a low is forecast to move east across southern parts of MS, AL, and GA, and perhaps across the FL Panhandle as well. Large-scale lift with this system will conditionally favor a few strong storms, but boundary-layer details will determine how productive of an event it is. Elsewhere, cooling temperatures aloft with an upper trough will impact the Pacific Northwest, with instability developing overnight favoring a few lightning flashes. ...MS/AL/FL Panhandle... A relatively cool and stable surface air mass will be in place over much of the Southeast during the day ahead of the surface low. However, southerly winds ahead of the low will bring at least mid 50s F dewpoints onshore across far southern MS, AL, and the FL Panhandle, possibly resulting in sufficient SBCAPE. Forecast soundings indicate up to 500 J/kg SBCAPE may develop immediately ahead of the cold front and dry slot aloft, where cooling aloft will be rapid. Large values of SRH will be present due to the warm advection atop the cool boundary layer, and will be reduced rapidly as the front approaches. There may be a brief window of opportunity where SBCAPE favor wind gusts or a tornado, and effective SRH remains strong. If this happens, isolated supercells may form. This event is highly conditional on the surface air mass and moisture return. If the air mass remains too cool along the coast, then little if any severe threat may develop. ...Coastal OR and northern CA... Increasing moisture may result in elevated CAPE across the region late in the day, with sporadic thunder possible. However, the strongest cooling aloft will occur close to 12Z Friday along the coast, and this is when models indicate non-zero SBCAPE may develop. Forecast soundings from various models are not in very good agreement regarding instability, but this area will need to be watched in subsequent outlooks. Shear will remain strong, and may conditionally favor a strong storm along the coast should instability be greater than currently forecast. ..Jewell.. 01/06/2021
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