Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Nov 21 2023 20:05:20 ACUS01 KWNS 212005 SWODY1 SPC AC 212003 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0203 PM CST Tue Nov 21 2023 Valid 212000Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF SOUTHEAST AL...WEST-CENTRAL/SOUTHWEST GA AND THE FL PANHANDLE... ....SUMMARY... A few brief tornadoes and isolated damaging gusts may occur across parts of the Southeast States through tonight. ....Southeast... A generally low probability but broad severe threat area will likely continue through tonight where strong low-level shear can persist amid weak instability. Through early evening, the primary corridor for a brief tornado or two appears to be focused near the GA/AL/FL border areas. Low-topped convection along/just ahead of the cold front might deepen sufficiently to acquire low-level updraft rotation, a scenario still supported by 18-19Z WoFS runs. Large low-level hodographs will generally be confined to the minimal/scant instability on the northern periphery of the surface-based buoyancy plume. Farther south, low-level hodographs will gradually shrink as flow becomes more veered where somewhat greater instability and richer low-level moisture are present into the FL Panhandle. See MCD 2282 for additional near-term forecast information. Elsewhere, the forecast appears reasonably on-track with no changes necessary. ...Grams.. 11/21/2023 ..PREV DISCUSSION... /ISSUED 1028 AM CST Tue Nov 21 2023/ ....Synopsis... A large mid/upper-level cyclone over the Great Lakes this morning will continue to move eastward today. A trailing, positively tilted upper trough extends across the Midwest into the mid/lower MS Valley and southern Plains. The primary surface low over the Midwest is also forecast to develop slowly east-northeastward toward the Lower Great Lakes through tonight. A trailing cold front will progress eastward today and tonight across the Southeast and Mid-Atlantic states as a secondary surface low eventually forms over VA/MD and develops quickly northeastward across the coastal Mid-Atlantic. ....Central to Northeast Gulf Coast States... Swaths of warm-advection-related precipitation and widespread cloud cover have hindered daytime heating so far this morning across southern AL, the FL Panhandle, and GA. Still, some clearing has recently been noted between the cold front ongoing precipitation. Most guidance suggests that surface temperatures reaching into the low 70s will be needed for sufficient boundary-layer destabilization to support surface-based thunderstorms. Even with this modest heating, poor lapse rates aloft will likely hinder the degree of MLCAPE across the warm sector this afternoon. This should temper updraft intensities to some extent. But, latest VWPs from area radars show rather strong low-level and deep-layer shear are still present across this region. Any robust convection that can develop along/near the cold front this afternoon could become supercellular, with an associated threat for a few tornadoes and isolated damaging winds. But, confidence remains low that enough instability will develop to support intense thunderstorms. Have therefore maintained the low-confidence Slight Risk across this region with minimal changes. ....Georgia into the Carolinas and Southeastern Virginia... Widespread cloud cover and areas of precipitation remain prevalent from GA into the NC/SC and VA, with a warm front/retreating wedge front delineating the northern extent of low-level moisture return. Instability should remain fairly weak through the period with northeastward extent from central/northern GA into the Carolinas. This limits confidence in thunderstorm intensities this afternoon. Still, a conditional threat for damaging wind gusts and perhaps a tornado or two exists with mainly linear convection that can develop/strengthen along the eastward-moving cold front this afternoon and evening. Late tonight, a low-topped line of convection may develop along the front from NC into southeastern VA and vicinity. While instability is forecast to remain minimal, strong flow at low/mid levels may still reach the surface through convective downdrafts. Have expanded the Marginal Risk for isolated damaging winds northward a bit based on this potential. Confidence in supercells developing across coastal/eastern NC in the last few hours of the period remains low. $$ = = = 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) .