Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed May 21 2025 17:28:46 ACUS02 KWNS 211728 SWODY2 SPC AC 211727 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Wed May 21 2025 Valid 221200Z - 231200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SOUTHERN PLAINS... ....SUMMARY... Severe storms are possible across parts of the southern Plains tomorrow/Thursday, with large hail the main threat. A few instances of 2+ inch diameter hail are possible. ....Synopsis... Broad northwesterly flow will prevail across much of the eastern U.S. as a mid-level trough ejects into the Atlantic, an upper ridge builds over the central CONUS, and a pronounced mid-level impulse traverses the northern Rockies tomorrow (Thursday). A surface low will track along the Mid-Atlantic Coastline while surface high pressure overspreads much of the Midwest into the Southeast, and lee troughing prevails across the southern Plains. Thunderstorms are likely along the East Coast and the FL Peninsula, in association with the departing upper trough. Storms developing ahead of a southward-sagging cold front in FL have the best potential for becoming strong to locally severe over the East Coast. At least scattered thunderstorms are also likely across the Southern Plains, northwestward into the northern Rockies, given lee troughing and low-level upslope flow. Thunderstorms developing along a baroclinic zone along the Red River will benefit from strong instability and adequate wind shear, and will have the potential to become severe. ....Southern Plains... Elevated thunderstorms are expected to develop in central OK within a warm-air advection regime, to the north of a west-to-east oriented baroclinic boundary, which is expected to be situated along the Red River during the morning/early afternoon hours. Through the day, storms are expected to propagate southward toward a surface-based airmass over northern TX, where upper 60s/low 70s F surface dewpoints beneath 8 C/km mid-level lapse rates will contribute to 2500-4000 J/kg MLCAPE. Low-level southerly flow, quickly veering to northwesterly and strengthening with height, will result in elongated hodographs with some low-level curvature near the baroclinic boundary. As such, the overall CAPE/shear parameter space will support supercells with large to very large hail potential. If a supercell can anchor along the baroclinic boundary, a tornado will also be possible. ....East Florida Peninsula... A southward-sagging cold front will begin to stall across the FL Peninsula during the afternoon hours, preceded by rich low-level moisture beneath 6.5-7.5 C/km mid-level lapse rates, which will boost MLCAPE over 2500 J/kg. Modest northwesterly mid-level flow impinging on the peninsula will encourage deep-layer speed shear over 40 kts, that in tandem with moderate to strong instability, will support multicells and transient supercells by afternoon. Large hail and strong, damaging wind gusts are the primary threats with the most intense storms. ....Northern Rockies... Scattered thunderstorm development is expected across central and northern ID into southwestern MT as strong forcing for ascent with the passing mid-level trough overspreads a deep, mixed boundary layer during the afternoon. Forecast soundings show inverted-v profiles extending up to 500 mb. As such, some downward momentum transport via evaporative cooling should encourage stronger wind gusts with the deeper storm cores. However, confidence is not high enough for severe gusts to introduce Category 1/Marginal risk probabilities at this time. ...Squitieri.. 05/21/2025 $$ = = = 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) .