Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 14 2022 12:54:44 ACUS01 KWNS 141254 SWODY1 SPC AC 141252 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0652 AM CST Wed Dec 14 2022 Valid 141300Z - 151200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN PARTS OF LOUISIANA...MISSISSIPPI AND ALABAMA...AND PORTIONS OF THE FLORIDA PANHANDLE... ....SUMMARY... Tornadoes (some strong) and damaging thunderstorm gusts are expected today and tonight across southern parts of Louisiana, Mississippi and Alabama, and portions of the Florida Panhandle. ....Synopsis... A large mid/upper-level cyclone covers much of the central CONUS, with a center apparent in moisture-channel imagery over central/ northern NE. That center is expected to meander slowly and erratically across the FSD/SUX region today, reaching northwestern IA by the end of the period. A basal shortwave trough -- initially located over parts of the TX Panhandle/South Plains to far west TX -- will turn eastward across north TX and OK today, reaching the Ozarks and Arklatex region by 00Z. Tonight the trough will weaken and accelerate northeastward across the mid Mississippi and lower Ohio Valleys, reaching WI and Lake Michigan by 12Z tomorrow. At the surface, 11Z analysis showed the main/occluded low near YKN, becoming stacked with the mid/upper-level circulation center. This low should move eastward with the vortex aloft and fill today, while a newer low forms on the occluded/cold front over the Mid-South and moves north-northeastward. By 00Z, this low should be over western KY, with cold front trailing across western TN, eastern MS and southeastern LA, and a synoptic warm front over parts of the Ohio Valley region. A marine warm front -- initially analyzed from near MOB northwestward over east-central MS -- will drift northeastward for a few more hours. This boundary then should accelerate northeastward over more of southern AL and the western FL Panhandle, while its northern fringe in eastern MS and west-central AL is overtaken by a prefrontal convective band. By 12Z tomorrow, the cold front should reach western SD and central/southwestern GA, still overtaking the Gulf warm front from northwest to southeast. The marine boundary may reach southwestern GA by 12Z, as the warm sector narrows from there southward over the eastern Panhandle/FL coastal bend region. ....LA/MS/AL/FL Panhandle/southwestern GA... Severe thunderstorms and a few tornadoes are possible through midday from southern LA across portions of southern/central MS and extreme southwestern AL, both from a primary convective band and smaller areas of more-gradually organizing cells located in the warm sector. For near-term coverage of severe-thunderstorm/tornado potential over western parts of the outlook area, refer to SPC tornado watch 587 and related mesoscale discussions. Scattered to numerous thunderstorms -- occasionally including embedded supercells, small bow/LEWP formations and QLCS mesovortices, will move slowly eastward across the outlook area this afternoon. This activity then should move quicker eastward late this afternoon into evening as the passing shortwave trough alters the strength and geometry of the ambient deep-layer flow. Continued, isolated to widely scattered development will be possible in subtle convergence/lift zones in the warm sector as well, some of which may interact with the relatively vorticity-rich marine front. Still, even the QLCS, embedded supercells and warm-sector convection will have access to rich low-level moisture and favorably enlarged hodographs, below a 55-65-kt LLJ. Effective SRH of 200-400 J/kg is expected in the warm sector, locally higher along the warm front, more than half of which should be in the lowest 500 m. Surface dewpoints in the mid 60s to low 70s F will continue across the warm sector. Despite modest deep-layer lapse rates and limitations on diabatic heating imposed by cloud cover, sufficient diurnal warming and theta-e advection are expected to foster weak CINH, with MLCAPE generally in the 1000-2000 J/kg range. A relatively maximized parameter space for tornado potential exists across the "enhanced" area, especially over parts of southern MS and southwestern AL today. The main uncertainty precluding a bump in tornado probabilities into "moderate risk" level this outlook cycle involves storm mode -- specifically, coverage of relatively discrete or semi- discrete supercells that could support more intense and longer- tracked tornadoes. The severe threat should shift eastward over parts of southern and perhaps central AL, and western/central FL Panhandle through evening and overnight. ...Edwards/Leitman.. 12/14/2022 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .