Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Feb 21 2024 12:46:45 ACUS01 KWNS 211246 SWODY1 SPC AC 211245 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0645 AM CST Wed Feb 21 2024 Valid 211300Z - 221200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE WESTERN OZARKS REGION AND OVER NORTH-CENTRAL PARTS OF ILLINOIS AND INDIANA... ....SUMMARY... Areas of strong thunderstorm development are possible across parts of the Ozark Plateau and adjacent Great Plains and across central Illinois to far western Indiana late Wednesday evening into early Thursday, with some risk for severe hail. ....Synopsis... The mid/upper-level pattern will trend more toward zonal through the period, as a well-developed southern-stream shortwave trough now near coastal southern CA moves quickly east-northeastward and penetrates a low-amplitude mean ridge over the central CONUS. This perturbation should cross the central/southern High Plains around 00Z, then deamplify somewhat as its northern part enters confluent flow and height falls ahead of a northern-stream trough crossing the Upper Midwest. By 12Z, the southern perturbation should reach from northern parts of IL/IN to southwestern MO and northwestern AR. At the surface, 11Z analysis depicted a wavy, slow-moving frontal zone from northernmost Lower MI across southern WI, through a weak low near DBQ, to near MKC, EMP and through a broad area of low pressure over western KS. Cyclogenesis is forecast today over the western KS region, shifting eastward across KS to near MKC by 06Z, trailing a cold front southwestward over northern OK. The Great Lakes/Mississippi Valley frontal segment should move southeastward then stall. A secondary low is possible along the cold front over northern OK by 06Z, when a warm to stationary front should extend from the MKC-area low across central parts of IL/IN. ....Ozarks to southern Great Lakes region... Isolated to scattered, elevated thunderstorms are expected to develop across portions of IL/IN and perhaps the western Ozarks region overnight, shifting/expanding eastward especially across the IL/IN region. Activity will attain greatest coverage after 06Z, and may pose a risk of marginally severe hail. Low-level warm/moist advection above the boundary layer is underway in a relatively dry, early-stage return-flow event across a broad corridor from the southern Plains to the Ohio Valley and southern Great Lakes States. The warm-advection plume should become more confluent and moist through today, and especially this evening into tonight, as it intensifies with the approach of the southern shortwave trough. Though the return-flow regime still will be far from mature or optimal, moist advection/transport will persist such that increasingly high-theta-e parcels are involved, and ultimately lifted to an LFC. The two areas with the most such progged lift are in and near the "marginal risk" outlooks. The northern area should have greater lift and thunderstorm coverage thanks to contribution from elevated, low-level frontal forcing, while theta-e and midlevel lapse rates will be greater above a relatively stable boundary layer in the southern area. Albeit with much-different vertical distributions, both areas should attain around 500-1200 J/kg MUCAPE, with greater effective shear in the northern area (35-45 kt), and a stronger proximate LLJ (45-55 kt) for the southern area across the Ozarks. However, despite a favorable environment for severe hail, given thunderstorms, the southern region appears more conditional because of stronger CINH, imparted by the same EML that is providing the high lapse rate. That implies less convective coverage, and some (not all) convection-allowing progs with weaker indicators of isentropic ascent indicate none -- despite greater moisture content in the potential inflow region. ...Edwards/Mosier.. 02/21/2024 $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .