Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 20 2023 17:28:41 ACUS02 KWNS 201728 SWODY2 SPC AC 201727 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Wed Sep 20 2023 Valid 211200Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTHERN OKLAHOMA AND NORTH TEXAS... ....SUMMARY... Severe thunderstorms producing damaging gusts and hail are possible across parts of southern Oklahoma into north Texas Thursday afternoon. Isolated strong to severe thunderstorms also are possible across parts of the central Plains and the southern High Plains. ....Synopsis... An upper low and attendant trough will slowly pivot across the Pacific Northwest and Intermountain West on Thursday. Ahead of this feature, diffluent upper flow will overspread much of the central/southern Plains vicinity. Several shortwave impulses are forecast to migrate across the Rockies and into the Plains, focusing potential for several areas of strong to severe thunderstorms Thursday afternoon and evening. ....Oklahoma into North Texas Vicinity... Morning clouds and possibly showers over parts of the OK/TX Panhandles into western/central OK will result limit destabilization for much of the period. However, strong heating to the south/east of this bubble of inhibition will result in a strong differential heating gradient across southern OK. Mid/upper 60s dewpoints and modest midlevel lapse rates will aid in moderate destabilization, with forecast MLCAPE values near 2000 J/kg. Deep-layer flow will not be particularly strong through about 600 mb, before rapidly increasing through the top of the cloud-bearing layer. Nevertheless, this will support effective shear magnitudes greater than 30 kt and organized cells/clusters are expected. Fairly long, straight hodographs suggest hail will be possible, though storm mode may preclude a more widespread large hail risk. Steep low-level lapse rates aided by temperatures warming into the low 90s, with a mixed boundary-layer to around 850 mb suggest isolated severe gusts are possible, and a small Slight (level 2 of 5) risk has been introduced. ....Central Plains Vicinity... Weak surface low development is forecast near the SD/WY border Thursday afternoon. A surface trough will extend southward into eastern CO/western KS. East of the surface trough, southeasterly low-level flow will transport low 60s dewpoints across portions of KS/NE and SD. This will support a band of moderate instability with MLCAPE values approaching 2000-2500 J/kg from south-central SD into western/central NE and portions of KS. Deep-layer flow is forecast to be somewhat modest, especially above around 700 mb. However, 25-35 kt 850-700 mb flow, and vertically veering wind profiles will result in enlarged/curved low-level hodographs. This should support a few organized cells/clusters with some risk for hail and strong gusts. Some guidance continues to indicate capping in the 850-700 mb, which could limit coverage and/or longevity of any better-organized convection. An outlook upgrade may be needed in subsequent outlooks, but confidence remains too low at this time to include a Slight (level 2 of 5) risk. ....Southern High Plains... East/southeast low-level flow to the east of the surface trough will maintain generally upper 40s to upper 50s surface dewpoints across eastern NM. However, steep midlevel lapse rates and strong heating will support a corridor of modest destabilization (MLCAPE around 1000-1500 J/kg) by afternoon. Vertically veering wind profiles with strong speed shear above 700 mb will support effective shear magnitudes greater than 40 kt with elongated/straight hodographs evident in forecast soundings. A few high-based cells are expected during the late afternoon/early evening. Any cells moving through the corridor of greater instability will pose a risk for hail given forecast shear and steep midlevel lapse rates. Steep low-level lapse rates and a deeply mixed boundary layer also will support a few strong gusts. Overall coverage is expected to remain limited, precluding higher severe probabilities. ...Leitman.. 09/20/2023 $$ = = = 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) .