Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Apr 21 2023 05:57:49 ACUS01 KWNS 210557 SWODY1 SPC AC 210556 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Fri Apr 21 2023 Valid 211200Z - 221200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF SOUTH AND EAST TX INTO THE LOWER MS VALLEY...AND ALSO FROM THE UPPER OH VALLEY INTO THE LOWER GREAT LAKES... ....SUMMARY... Isolated severe thunderstorms will be possible today across parts of the upper Texas coastal plain into the lower Mississippi Valley, and also across deep south Texas. Large hail and locally damaging gusts will be possible. A few strong storms capable of damaging gusts will also be possible across the upper Ohio Valley into the lower Great Lakes region. ....Synopsis... A deep longwave trough will remain in place across the central CONUS today. One embedded shortwave trough will move into Ontario from the upper Great Lakes region during the day today, while another embedded shortwave and attendant midlevel jet maximum move east-southeastward from the southern Plains toward the lower MS Valley. A deep-layer cyclone will move slowly eastward across the upper Great Lakes region, while one or more surface waves may develop along a cold front that will be draped from south TX into the lower MS Valley, OH Valley, and lower Great Lakes. ....Parts of south and east TX into the lower MS Valley... Considerable uncertainty remains regarding the evolution of convection across TX into the lower MS Valley overnight, prior to the start of the forecast period at 12Z this morning. A weakening MCS may be ongoing near the upper TX and LA Gulf Coasts into the northwest Gulf of Mexico, with some potential for elevated redevelopment in the wake of the MCS. Steep midlevel lapse rates, moderate MUCAPE, and sufficient deep-layer shear will support some threat for hail and isolated damaging gusts with any stronger elevated convection during the morning. Wind profiles will remain favorable for organized storms through the day, so depending on the extent of destabilization this afternoon, isolated severe storms may redevelop from LA into MS along the front. The environment farther southwest into deep south TX is likely to be relatively undisturbed by earlier convection, and moderate to strong buoyancy is likely to be in place during the afternoon. With generally weak surface convergence and limited large-scale ascent, storm coverage is expected to remain isolated at best, but sufficient deep-layer shear (with northwesterly flow aloft) will support a conditional risk for a supercell or two with large-hail potential. ....Upper OH Valley into the lower Great Lakes region... Low-level moisture will remain limited from the OH Valley into the Great Lakes region, but relatively strong diurnal heating will support MLCAPE increasing into the 250-500 J/kg range this afternoon, with scattered thunderstorm development expected. Steep low-level lapse rates and modestly enhanced low-level flow will support the potential for isolated strong/damaging gusts before the threat diminishes with the onset of nocturnal cooling this evening. ...Dean/Bentley.. 04/21/2023 $$ = = = 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) .