Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Sep 18 2023 06:01:49 ACUS02 KWNS 180601 SWODY2 SPC AC 180600 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Sep 18 2023 Valid 191200Z - 201200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SOUTHERN PLAINS... ....SUMMARY... Scattered severe thunderstorms are possible Tuesday and Tuesday night across portions of the southern Great Plains. Large to very large hail and severe gusts are the primary hazards. ....Synopsis... Relatively zonal mid-level flow will overspread the central and southern CONUS as an upper trough gradually amplifies across the northwestern U.S. tomorrow/Tuesday. However, multiple mid-level perturbations embedded within the zonal flow will eject into the southern Plains by Tuesday afternoon/evening, supporting pronounced lee troughing and some north-northwestward transport of low-level moisture. The mid-level perturbations overspreading the moisture will promote deep-layer ascent, supporting scattered strong to severe thunderstorms over the southern Plains. ....Portions of the Southern Plains... By afternoon, the approach of a mid-level perturbation will support strengthening low-level flow and the northward transport near 60 F surface dewpoints ahead of an eastward-advancing dryline in western OK/northwestern TX. 7-8 C/km mid-level lapse rates overspreading near 60 F dewpoints will boost SBCAPE into the 2000-3000 J/kg range by afternoon peak heating. Meanwhile, 30-40 kts of southwesterly 850 mb flow overspread by 30-40 kt 500 mb westerlies will support mostly straight, elongated hodographs and 30-40 kts of effective bulk shear. Splitting supercells are expected to initiate off of the dryline. Given 20-30 F surface temperature/dewpoint spreads and modest low-level shear accompanying these supercells, the tornado risk should be limited, but large to very large hail is possible. Some of the latest guidance also indicates the potential for supercells to merge and grow upscale into an MCS by evening, especially over central OK. Should this occur, severe gusts would become the main concern, at least with the leading round of storms. However, by evening, a veering but strengthening low-level jet atop earlier storm outflows may encourage back-building convection in central OK. Isolated severe hail/wind is possible with these storms. ....Southern Florida Peninsula... Latest high-resolution guidance consensus depicts scattered thunderstorms developing along the southeastern FL coast by Tuesday afternoon, and are poised to drift westward in tandem with a surface sea-breeze boundary. Forecast soundings depict 1000-1500 J/kg of tall/thin SBCAPE profiles. While vertical wind profiles should be weak overall, some of the forecast soundings depict modestly elongated upper-level hodographs, so some storm organization and associated potential for a damaging gust or two cannot be completely ruled out. However, confidence in this scenario is modest at best, precluding severe probabilities at this time. ...Squitieri.. 09/18/2023 $$ = = = 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) .