Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Sep 18 2023 17:34:22 ACUS02 KWNS 181734 SWODY2 SPC AC 181732 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1232 PM CDT Mon Sep 18 2023 Valid 191200Z - 201200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF OKLAHOMA AND ADJACENT NORTH TEXAS... ....SUMMARY... Scattered severe thunderstorms are possible Tuesday and Tuesday night across portions of the southern Great Plains. Large to very large hail and severe wind gusts are the primary hazards. ....Synopsis... Relatively zonal mid-level flow is expected across much of the U.S. Tuesday, though an upper trough is progged to dig southward across British Columbia toward -- and eventually into -- the Pacific Northwest. Otherwise, multiple mid-level perturbations embedded within the quasi-zonal flow will cross central portions of the country. At the surface, lee troughing is generally progged across the Plains, as a result of the background upper-level westerlies across the interior West. Some northward transport of low-level moisture will support diurnally maximized destabilization, which -- combined with ascent provided by the aforementioned mid-level perturbations -- will support rounds of scattered strong to severe thunderstorms over the southern Plains during the period. ....Portions of the Southern Plains... Northward advection of low-level moisture, combined with diurnal heating beneath steepening mid-level lapse rates accompanying the short-wave troughing aloft will support moderate destabilization. By late afternoon, 1500 to 2000 J/kg mixed-layer CAPE is expected across much of Oklahoma and adjacent portions of western and central Texas. Meanwhile, with around 30 kt southwesterly 850 mb flow beneath 30-40 kt 500 mb westerlies, shear will support organized/rotating storms with initial convective development, with later, upscale growth into an MCS possible, that would shift across central Oklahoma and possibly adjacent portions of Texas. Other, more isolated storms may also develop southwestward along the trough/dryline, as far southwestward as roughly the Concho Valley area, where a few storms with mid-level rotation may evolve. Given the likelihood for supercells within the moderately unstable environment, large to very large hail will be possible with the initial convection, though locally damaging wind gusts may also occur given the deep mixed layer, and resulting sub-cloud evaporative effects. Damaging wind potential may continue into the overnight hours, particularly if storms grow upscale as anticipated. Additionally, redevelopment of smaller clusters of storms should occur near convective outflows as a nocturnal low-level jet strengthens, resulting in multiple rounds of storms in some areas. ....Southern Florida Peninsula... Latest guidance indicates that scattered thunderstorm development will occur Tuesday afternoon, initially focused near the southeastern FL coast but drifting inland with time in tandem with sea-breeze boundary advance. Model soundings depict 1000-1500 J/kg, though with relatively weak lapse rates aloft. Shear should remain rather modest, suggesting weakly organized storms at best. Still, potential for a damaging gust or two cannot be completely ruled out during the afternoon. ...Goss.. 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) .