Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 21 2023 17:31:10 ACUS02 KWNS 211731 SWODY2 SPC AC 211729 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Mon Aug 21 2023 Valid 221200Z - 231200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR SOUTH-CENTRAL INTO DEEP SOUTH TX...PARTS OF THE UPPER GREAT LAKES...NORTHWEST AZ INTO UT AND SOUTHWEST WY... ....SUMMARY... Storms with gusty winds and possibly a tornado or two will be possible across parts of south Texas on Tuesday, in association with a potential tropical cyclone. Isolated strong to severe storms will also be possible from northern Arizona into Utah and southwest Wyoming, and also across the upper Great Lakes region. ....South-central into Deep South TX... PTC 9 is currently forecast by NHC to strengthen into a tropical storm early Tuesday morning. The center of this system is forecast to be approaching the south TX coast at the start of the period. As tropical moisture and increasing low-level flow/shear spreads across south-central into Deep South TX in association with this system, transient low-topped supercells will become possible, potentially posing a threat for a tornado or two and isolated strong/severe gusts. The greatest relative threat is expected across the typically favored northeast quadrant of the cyclone, though the magnitude of the threat remains uncertain, pending the landfall intensity of the system and strength of any notable diurnal destabilization. ....Upper Great Lakes vicinity... One round of elevated convection will be possible Tuesday morning from northern WI into parts of upper MI, with another round possible late Tuesday night into Wednesday morning across the same general region, potentially extending into parts of lower MI. Both rounds will occur to the cool side of a slow-moving warm front and be driven by a moderate to strong nocturnal low-level jet. Midlevel lapse rates and MUCAPE will likely be greater for the second round of convection late in the period (potentially increasing above 2000 J/kg), with moderate northwesterly midlevel flow along the periphery of a strong upper ridge providing sufficient effective shear for organized storms. Isolated hail will be possible with the strongest storms, both early and late in the forecast period. MCS development cannot be ruled out late in the period, but low-level stability should generally tend to limit severe-gust potential. ....Great Basin vicinity... A moisture plume and a belt of somewhat enhanced low/midlevel flow will persist across portions of the Great Basin on Tuesday, along/east of an ejecting upper-level trough that will move from northern CA into the northern Rockies. Scattered thunderstorms will be possible within this regime through the day into the evening. While deep-layer shear will be sufficient to support organized convection, rather weak midlevel lapse rates and potentially limited heating may limit destabilization and the overall severe threat. If MLCAPE can increase into the 500-1000 J/kg range (which remains uncertain), a few organized clusters and/or marginal supercells may evolve, with a threat of isolated severe gusts and possibly a brief tornado. ....Interior Northwest... Scattered thunderstorm development is possible Tuesday afternoon from eastern OR into ID and western MT, associated with a mid/upper-level shortwave trough moving across the Pacific Northwest. Deep-layer shear will be sufficient to support somewhat organized convection, but it remains uncertain as to whether instability will be sufficient to support a severe hail/wind threat. ...Dean.. 08/21/2023 $$ = = = 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) .