Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Sep 18 2023 07:29:52 ACUS03 KWNS 180729 SWODY3 SPC AC 180728 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Mon Sep 18 2023 Valid 201200Z - 211200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE SOUTHERN PLAINS... ....SUMMARY... Isolated strong to severe thunderstorms are possible across the southern Plains Wednesday afternoon and evening. ....Synopsis... Embedded perturbations within zonal mid-level flow will de-amplify as they move away from the southern Plains, followed by an upper ridge impinging on the Plains states by Wednesday afternoon. However, amplification of a mid-level trough across the Interior West will prompt surface lee troughing and southerly low-level moisture return across the Plains states, fostering at least scattered thunderstorm potential. Latest guidance consensus suggests that adequate buoyancy may develop across the warm sector over portions of the southern Plains to support isolated strong to potentially severe thunderstorms Wednesday afternoon and evening. ....Portions of the southern Plains... Scattered thunderstorms are expected to be ongoing across central OK into north TX at the start of the period. As the afternoon progresses, upper ridging should build over the southern Plains, coinciding with weakening of the early-day storms and increased surface heating. As surface lee troughing intensifies over the southern Plains, 60-65 F surface dewpoints should advect northwestward beneath 7-8 C/km mid-level lapse rates, with MLCAPE potentially reaching 2000-2500 J/kg by afternoon peak heating. Strengthening northwesterly mid to upper flow with the approaching upper ridge will contribute to elongated hodographs and 30-40 kts of effective bulk shear. Given early day convection and expected height rises with the approaching upper ridge, overall confidence in an organized round of severe thunderstorms is low. Nonetheless, any storm that manages to develop and become sustained in the aforementioned kinematic/thermodynamic environment may become briefly supercellular, supporting an isolated severe hail/wind risk. ....Portions of the northern Plains into the Upper MS Valley... Synoptic-scale deep-layer ascent and vertical shear is expected to be weak across the northern Plains into the Upper MS Valley, limiting convective coverage. However, 7 C/km mid-level lapse rates overspreading 55-60 F surface dewpoints along a near-stationary surface boundary will boost SBCAPE into the 1000-1500 J/kg range. It is not out of the question that a couple of stronger thunderstorms could produce some hail/wind approaching severe limits. However, confidence in this scenario is too low to warrant severe probabilities this outlook. ...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) .