Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Nov 27 2024 12:45:52 ACUS01 KWNS 271245 SWODY1 SPC AC 271244 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0644 AM CST Wed Nov 27 2024 Valid 271300Z - 281200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER CENTRAL MISSISSIPPI TO CENTRAL AND NORTHERN ALABAMA...AND PARTS OF THE WESTERN/CENTRAL FLORIDA PANHANDLE TO SOUTHWESTERN GEORGIA... ....SUMMARY... Isolated strong to severe storms are possible late tonight into early Thanksgiving morning, over central Mississippi to central and northern Alabama, and parts of the western/central Florida Panhandle to southwestern Georgia. ....Synopsis... A progressive, nearly zonal middle/upper-level pattern over much of the CONUS will become more cyclonically curved east of the Rockies through the period. Contributing to this will be a positively tilted shortwave trough -- evident in moisture-channel imagery from central WY across northern parts of UT/NV. This perturbation should move rapidly across the central Rockies today, reaching southern parts of KS and CO by 00Z. The trough then should pivot east- northeastward and elongate, reaching the Ohio Valley and Ozarks by 12Z tomorrow. 11Z surface analysis showed an area of low pressure over the northern TX Panhandle into northeastern NM, along and south of a cold front extending into the Sangre de Cristos between RTN-TAD. By 00Z, the low should consolidate and reach central or west-central AR, with cold front southwestward across north-central and west- central TX to southeastern NM. The main low should redevelop to the northeast over KY tonight, then move to a 12Z position roughly near MGW, with cold front then extending to near the NC/TN line, northern AL, south-central MS, southeastern LA, shelf waters off the middle/ upper TX Coast, to deep south TX. ....MS/AL... Widely scattered to scattered thunderstorms are expected to develop near the cold front overnight -- most likely after 06Z -- with marginal potential for a tornado, isolated damaging winds or severe hail. Despite the veered (southwesterly) surface flow ahead of the front, a 40-50-kt west-southwesterly LLJ should contribute to long low- level hodographs with some curvature. That will foster 200-300 J/kg effective and 0-1-km SRH values (locally higher), amidst 45-55-kt effective-shear magnitudes and a narrow, front-parallel plume of 500-1000 J/kg MLCAPE. However, with the veering prefrontal flow, lift along the front will be compromised to some extent, causing uncertainty on storm coverage. Also, weak boundary-layer lapse rates -- characteristic of this time of day in marginal-moisture scenarios -- may yield long time windows for convective deepening, potentially limiting storm strength at maturity if activity merges with other precip or moves into weaker instability, as progged. Given these concerns, the threat continues to appear limited but nonzero in nature, and has been removed from previous northwestern areas where it now appears frontal passage will precede substantial deep development. ....Coastal FL Panhandle to southwestern GA... Isolated to widely scattered thunderstorms are possible late tonight, with a low-end but not negligible tornado and strong/ severe-gust threat. Development would be concentrated near a maximum in boundary-layer lift accompanying southwest/northeast-oriented, low-level, prefrontal confluence axis, undergoing theta-e advection from favorably modifying maritime air on the north rim of the Loop Current. Modified forecast soundings show progressive lift and erosion of a stable/capping layer from about 650-800 mb, located beneath 500-1000 J/kg MLCAPE, as warm advection persists below that stable layer and lift continues along the kinematic boundary. This may support development of a few thunderstorms after 06Z, with enough low-level and deep shear on the east side of the boundary (where surface winds will be relatively backed) to support supercell potential, amidst roughly 40 kt effective-shear magnitudes and 100-150 J/kg of 0-1-km SRH. ...Edwards/Leitman.. 11/27/2024 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .