Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jun 04 2023 12:50:00 ACUS01 KWNS 041249 SWODY1 SPC AC 041248 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Jun 04 2023 Valid 041300Z - 051200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE SOUTHERN APPALACHIANS/TENNESSEE VALLEY REGION...AS WELL AS PARTS OF SOUTH TEXAS... ....SUMMARY... Damaging to isolated severe gusts, along with isolated severe hail, are possible over the southern Appalachians/Tennessee Valley region, as well as parts of south Texas. ....Synopsis... Blocking aloft, with slight retrogression, will continue through this period. In moisture-channel imagery, a mid/upper-level high was apparent near Winnipeg, with broad anticyclone extending across much of south-central Canada and the north-central CONUS. The high should drift westward to near the southern MB/SK border by 12Z tomorrow. As this occurs, a pronounced cyclone centered south of ME and east of MA will drift erratically for most of today before slowly turning southward to southeastward overnight. Farther southwest, a weak perturbation apparent over the western Carolinas and eastern TN should drift southwestward today. A quasistationary, negatively tilted, weak upper trough will persist from a small cyclone over northern UT southeastward across the southern Rockies/High Plains to the Red River and Sabine Valleys. Several embedded, slow-moving perturbations are likely to meander erratically within the associated broad height weakness, which extends a couple hundred miles either side of the axis. Meanwhile, a few additional vorticity lobes of varying sizes and strengths may be convectively generated today and tonight. At the surface, the synoptic pattern remains rather messy and nebulous over most of the CONUS east of the Rockies, save for a "back-door" cold front drawn at 11Z from southern NC across northern GA then northward over eastern TN/KY to near Lake Michigan. This boundary should drift westward to southwestward and become more diffuse through the period. A dryline was drawn from southeastern CO across eastern NM to the Pecos Valley area of west TX. ....Southern Appalachians/Tennessee Valley... Widely scattered to scattered thunderstorms with isolated, marginal severe potential should develop this afternoon near the frontal zone and move southwestward across the area. Subtle large-scale ascent near the mid/upper perturbation will contribute to destabilization aloft today. This will occur atop a boundary layer characterized by weak CINH, diurnal heating/destabilization, and surface dewpoints generally in the mid 50s to low 60s F after some mixing. 500-1200 J/kg MLCAPE should develop atop inverted-v thermodynamic profiles in low levels, supporting downdraft acceleration to surface. Though deep layer winds and vertical shear will be weak, strong to perhaps isolated severe downbursts may cause some wind damage -- especially with any localized, cold-pool-aided thunderstorm clusters that may develop. Hailstones up to near severe limits also are possible. ....South TX... Thunderstorms are possible this afternoon into evening over a large part of the corridor near the upper trough, from the Great Basin to the western Gulf Coastal Plain -- and isolated severe gusts or hail cannot be ruled out almost anywhere over that vast swath. However, within an expansive favorable-moisture/weak-shear regime, relative concentrations of multicellular convection may focus severe potential somewhat better on the mesoscale. The most probable area for that to happen currently appears to be across parts of south TX near the outflow boundary, and over the higher terrain of northeastern MX, each of which may focus development and southeastward propagation of strong thunderstorms southwest of the trough aloft (in modest, west to northwest flow aloft). Strong heating of a favorably moist, weakly capped boundary layer is expected throughout the midday into afternoon, with surface dewpoints generally in the 60s F, leading to areas of 2000-3000 J/kg MLCAPE. Weak shear will temper organization somewhat, though one or two bands/clusters of convection may aggregate upscale and offer damaging to severe gusts after an initial, isolated hail threat in more-discrete stages. ...Edwards/Smith.. 06/04/2023 $$ = = = 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) .