Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jan 05 2023 20:01:29 ACUS01 KWNS 052001 SWODY1 SPC AC 051959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0159 PM CST Thu Jan 05 2023 Valid 052000Z - 061200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... Severe thunderstorms are not expected today. ....San Joaquin Valley and Southern CA Coast... Latest surface analysis shows a surface trough extending southward across the central San Joaquin Valley toward the LA Basin this afternoon. Along/behind this feature, HCRs (horizontal convective rolls) are streaming northeastward from San Luis Obispo, Ventura, and Los Angeles Counties toward the San Joaquin Valley -- indicative of boundary-layer destabilization amid lower/middle 50s dewpoints. Continued heating amid these HCRs and increasing large-scale ascent are favoring shallow convective showers, with only isolated lightning flashes thus far. Over the next couple of hours, additional deepening of this convection is possible as instability increases, and an isolated strong to locally severe storm cannot be entirely ruled out given 30-35 kt of 0-1 km bulk shear (per regional VWP data). The main concerns would be locally strong gusts and small hail. However, backed (albeit weak) surface winds in the San Joaquin Valley and increased low-level shear could support a brief tornado. The risk of a strong to severe storm would ultimately be greater if a band of convection were to develop and overspread the area -- as depicted by certain high-resolution model solutions. Overall, confidence in the development of organized severe storms remains too low for severe probabilities. Farther north across northern/central CA, embedded cells within a broad precipitation field will also be capable of locally strong gusts and small hail this afternoon, though the overall severe risk appears low. ...Weinman/Mosier.. 01/05/2023 ..PREV DISCUSSION... /ISSUED 1025 AM CST Thu Jan 05 2023/ ....Synopsis... A midlevel cyclone, evident in water vapor imagery will continue eastward across the Great Lakes vicinity through the period, while related large-scale troughing persists over the eastern CONUS. An embedded midlevel speed maximum will lift northeastward from the Southeast and eventually off the Mid-Atlantic coast, allowing the tail-end of a cold front to continue southward across the central/southern FL Peninsula. Moist/unstable boundary-layer conditions will continue supporting isolated thunderstorms along/immediately ahead of the southward-moving front today. While 30-40 kt of effective shear obliquely-oriented to the front could favor a loosely organized multicell cluster or two over central FL early this afternoon, limited large-scale ascent and poor midlevel lapse rates should temper the severe risk. Farther west, water vapor imagery and regional VWP data depict a pronounced, midlevel shortwave trough accompanied by strong west-southwesterly flow aloft tracking eastward over the CA coast. As associated strong midlevel height-falls (90m per 12hr) continue overspreading CA and parts of the Great Basin, isolated to widely scattered thunderstorms should spread eastward across the region into the overnight hours. Cold midlevel temperatures atop lower 50s boundary-layer dewpoints could yield pockets of weak surface-based instability (especially over the western portions of CA this afternoon). These conditions, coupled with 25-35 kt of effective shear, could support a few embedded cells capable of small hail and locally strong gusts. However, the weak instability/poor low-level lapse rates should generally limit storm intensity -- precluding severe probabilities. $$ = = = 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) .