Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 18 2023 19:58:21 ACUS01 KWNS 181958 SWODY1 SPC AC 181956 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Fri Aug 18 2023 Valid 182000Z - 191200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE DESERT SOUTHWEST...MONTANA...AND NEW ENGLAND... ....SUMMARY... Isolated strong to severe wind gusts are possible, mainly from late afternoon to mid-evening across parts of Montana, the Desert Southwest, and New England. ....20Z Update... The general thunderstorm area has been trimmed across New England, but no changes have been made to the Marginal Risk areas. Uncertainty remains regarding potential for substantial redevelopment of deep convection across New England, but isolated damaging gusts cannot be ruled out if any stronger storms can be sustained. Storms capable of producing localized severe gusts remain possible later this afternoon into this evening across parts of MT and the Southwest. See the previous discussion below for more information, and MCD 2013 regarding the near-term threat across Montana. ...Dean.. 08/18/2023 ..PREV DISCUSSION... /ISSUED 1129 AM CDT Fri Aug 18 2023/ ....MT... Despite lingering mid-level clouds tempering insolation to some extent, surface temperatures should still heat into the 90s across eastern MT by late afternoon. Large-scale ascent attendant to a shortwave trough tracking east from southern BC to the lee of the Canadian Rockies should largely hold north of the international border. But low-level speed convergence should increase this evening along a trailing surface cold front and this may aid in sustaining isolated thunderstorms off the higher terrain of southwest MT. While MLCAPE should remain meager (at or below 500 J/kg), very deeply mixed profiles east of the terrain will support a threat for isolated severe wind gusts. ....Desert Southwest.... Weak deep-layer shear will be the primary limiting factor to a more organized severe wind threat, with mainly 15-25 kt 500-mb southerlies between a stout anticyclone over the southern Great Plains and a cutoff low off the southern CA coast. Scattered thunderstorms developing over the higher terrain, aided by a high PW air mass emanating north from the Gulf of CA, will pose a threat for sporadic severe wind gusts as they spread/collide northward within the deeply mixed environment across the lower deserts. ....New England... In the wake of this morning's tornadic supercell, low-level winds have substantially veered and weakened ahead of a north to south-oriented cold front pushing east into western New England. With a wedge of greater insolation between it and cloud cover associated with the early-day convection that is now largely off the coast, MLCAPE of 500-1000 J/kg should redevelop over the next few hours and support deepening convection along the front. While adequate deep-layer shear will remain, the increasingly poor low-level wind fields should mitigate an organized damaging wind threat. Still, a few strong gusts remain possible until the front reaches the coast. $$ = = = 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) .