Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 21 2023 12:49:00 ACUS01 KWNS 211248 SWODY1 SPC AC 211247 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Sun May 21 2023 Valid 211300Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS THE INTERIOR NORTHWEST AND NORTHERN ROCKIES... ....SUMMARY... Severe thunderstorms are possible across portions of the interior northwest into western Montana. Large hail and isolated damaging gusts will be possible with these storms. ....Interior Northwest/northern Rockies this afternoon/evening... A midlevel shortwave trough off the WA/OR coasts this morning will progress eastward/inland through tonight, along with an associated cold front. Around the northwest periphery of a midlevel high over the northern Great Basin, a plume of low-midlevel moisture has supported primarily diurnal convection the past few days across OR/WA. The threat for afternoon/evening thunderstorms will persist today and shift eastward compared to prior days, with storm coverage augmented by forcing for ascent in the vicinity of the cold front. Midlevel lapse rates in excess of 7 C/km, surface heating in cloud breaks, and boundary-layer dewpoints in the low-mid 50s will all contribute to MLCAPE near 1000 J/kg this afternoon in advance of the front. The moderate buoyancy and effective bulk shear of 25-35 kt/relatively straight hodographs will favor a mix of multicell clusters and supercells capable of producing large hail and damaging winds for a few hours later this afternoon into this evening, from eastern OR into northern ID and vicinity. ....Southeast GA into the central FL peninsula this afternoon... A weak cold front will move slowly southeastward toward the southeast Atlantic coast, in association with a weak midlevel trough now over north GA and the Carolina Piedmont. Farther south, colliding sea breezes are expected near the middle of the FL peninsula this afternoon. These boundaries will support thunderstorm development this afternoon from southeast GA into FL. While there will be a little enhancement to deep-layer vertical shear with somewhat stronger flow aloft, but low-level flow is expected to remain rather weak, and midlevel lapse rates will be poor. These factors will limit the potential for isolated severe storms. ....Southern High Plains this afternoon/evening... Rather modest low-level moisture and midlevel lapse rates (by late May standards) will support weak-moderate buoyancy (MLCAPE of 500-1000 J/kg) this afternoon along and east of a weak lee trough. A diffuse midlevel trough will move across NM through this afternoon, and combine with convergence along the lee trough to support scattered thunderstorms. The modest lapse rates and relatively weak vertical suggest that severe storms are unlikely. ...Thompson/Broyles.. 05/21/2023 $$ = = = 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) .