Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 20 2023 19:41:06 ACUS01 KWNS 201941 SWODY1 SPC AC 201939 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Aug 20 2023 Valid 202000Z - 211200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST CA INTO THE LOWER CO VALLEY... ....SUMMARY... A couple tornadoes are possible across the Lower Colorado Valley and southern Mojave Desert vicinity through around dusk. ....20z Update... Only minor adjustments have been made to the 2 percent tornado probabilities over AZ. Otherwise, the previous outlook remains on track. See previous discussion below for more details, and reference MCD 2017 for short term severe/tornado hazard information. ...Leitman.. 08/20/2023 ..PREV DISCUSSION... /ISSUED 1119 AM CDT Sun Aug 20 2023/ ....Desert Southwest... The conditional TC-tornado environment evident over the northern Gulf of CA and northwest Sonora is expected to spread north-northwest across the Lower CO Valley and southern Mojave Desert vicinity. The primary corridor of concern will be across southeast CA and adjacent portions of western AZ/southern NV this afternoon into early evening. Here, meager MLCAPE from 300-600 J/kg should develop with some thinning of the cloud canopy amid upper 60s to low 70s boundary-layer dewpoints. This will remain coincident with an enlarged low-level hodograph in the northeast quadrant of weakening TC Hilary. Most 12Z HREF guidance struggles to maintain deep convection, but sustained low-topped convection could acquire updraft rotation and be capable of producing a brief tornado. This threat will end from south to north during the evening as low-level drying and decreasing hodograph curvature occurs within the southeast quadrant of the remnant TC. Relatively greater likelihood of deeper convective development is anticipated during the mid to late afternoon along the differential boundary-layer heating corridor from southeast AZ to southwest UT. This zone will be within the pronounced west to east gradient of high to low PW and consequently along the fringe of meager MLCAPE. At least isolated thunderstorms should form off the higher terrain and possess progressively weaker low-level SRH relative to the west/south. Some 12Z HREF members do depict a 2-5 km UH signal which makes sense given adequate shear within this layer. While mid-level rotation will be possible, isolated severe wind gusts should be the primary threat, particularly with any cells/small clusters that can propagate towards the more deeply mixed environment to the north-northeast. $$ = = = 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) .