Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 12 2023 12:24:20 ACUS01 KWNS 121224 SWODY1 SPC AC 121222 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0722 AM CDT Tue Sep 12 2023 Valid 121300Z - 131200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE EAST AND SOUTHWEST... ....SUMMARY... Isolated severe thunderstorms will be possible, mainly this afternoon into tonight, across parts of the southern Appalachians to Mid-Atlantic States, south Georgia to central Florida, and south Arizona to southwest New Mexico. ....Southern Appalachians to the Mid-Atlantic States... A large-scale upper trough from James Bay to the Upper Midwest will gradually pivot east and become centered over the Great Lakes by early Wednesday. This will induce increasing mid-level height falls across much of the Northeast and Mid-Atlantic States, especially during the latter half of the period, with weaker height falls trailing southwest towards the TN Valley. Moderate differential diabatic heating will occur today ahead of a weak southwest/northeast-oriented baroclinic zone. This should aid in scattered thunderstorms developing towards early afternoon from the TN Valley to the central Appalachians. Poor mid-level lapse rates will limit overall buoyancy and updraft vigor, but at least weak buoyancy coupled with 25-35 kt effective bulk shear should support multicell clusters and an attendant threat for sporadic damaging winds. While spatial decrease in the threat is expected after dusk, an uptick may occur tonight as greater mid-level height falls overspread richer low-level moisture over the Chesapeake and Delmarva regions. Low-level mass response may be adequate for a few transient supercells, that should generally remain weak, but may pose a low-probability brief tornado threat. ....South GA to central FL... Large-scale pattern will not change appreciably across the area today. A minor mid-level trough over the north-central Gulf will slowly progress east and remain well offshore through the period. Downstream of this feature, 500-mb west-southwesterlies of 15-25 kts will persist and support short-duration/transient organization. As surface temperatures warm into the upper 80s to low 90s, isolated to scattered thunderstorms will develop along the sea breezes and collide inland. Ample buoyancy with MLCAPE of 2000-2500 J/kg will support vigorous downdrafts and sporadic wind gusts from 45-65 mph, along with marginally severe hail from 0.75 to 1.25 inches. ....Southern AZ to southwest NM... A belt of confluent mid-level westerlies will yield a swath of 30-35 kt flow across the region, supporting potential for isolated severe thunderstorms from late afternoon through tonight. Mid-level lapse rates will be modest and timing/extent of large-scale ascent appears nebulous with multiple rounds of thunderstorm development from this morning through tonight. A plume of weak to moderate buoyancy should become established this afternoon south of the Mogollon Rim. Scattered thunderstorms seem most likely during the late afternoon and evening within the buoyancy gradient and across the higher terrain. Sporadic occurrences of 50-60 mph wind gusts along with marginally severe hail around 1 inch will be possible through the period. ...Grams/Mosier.. 09/12/2023 $$ = = = 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) .