Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Sun Nov 19 2023 10:18:00 ACUS01 KWNS 191240 SWODY1 SPC AC 191238 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0638 AM CST Sun Nov 19 2023 Valid 191300Z - 201200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL/EASTERN OKLAHOMA... ....SUMMARY... Marginally severe hail may occur with evening/overnight thunderstorms in parts of Oklahoma. ....Synopsis... In mid/upper levels, a broad area of cyclonic flow, with multiple shortwaves and vorticity lobes of varying intensity, is apparent in moisture-channel imagery over much of the western/central CONUS. Those perturbations will consolidate into a large, complex cyclone by 12Z tomorrow, extending from the central Plains to the southern High Plains. The strongest of the shortwave troughs is located in the rear side of this configuration, from offshore of Vancouver Island southeastward to parts of NV. The southern part of this perturbation is expected to dig southeastward across the Four Corners region around 00Z, reaching the TX Panhandle and eastern/ southern NM by 12Z. In response, an elongated area of surface low pressure -- analyzed at 11Z near the CO/KS border -- should consolidate and move/ redevelop erratically southward toward west-central/southwestern OK by 06Z, pivoting over central OK by the end of the period. As the cyclogenesis proceeds in a residual continental/polar (cP) airmass, surface frontal features (especially warm frontal) will be nebulous this period. Still, a strengthening cold front should extend from the low across parts of northwest/west-central TX by 12Z, overtaking a developing dryline from north to south. ....OK... Multiple rounds of thunderstorms are possible today and tonight over the southern Plains, from southern KS across central/eastern OK to north-central/northeast TX. Activity will be supported by a fetch of elevated low-level warm advection and strong moisture transport -- above a relatively stable boundary layer. Return flow will be relatively immature -- even above the surface -- as upstream trajectories of cP air that followed the last frontal passage continue to modify. Buoyancy should diminish northward into more precip-laden air, with less-modified inflow parcels. Deep combined lift (from low-level warm advection, divergence-related jet dynamics aloft, and shots of midlevel DCVA preceding the main trough), will weaken southward. The most favorable overlap between those processes, in support of sustained/organized thunderstorms, still appears to be in or very near the outlook area, especially this evening and tonight. That is when low-level/inflow-layer theta-e and cooling aloft each will be greatest, and LFC lowest (but still elevated atop a stable boundary layer). As lapse rates above the boundary layer steepen rapidly tonight, MUCAPE should strengthen into the 500-1000 J/kg range -- rooted near 850 mb and distributed well through the hail-growth zone -- with effective-shear magnitudes peaking in the 30-40-kt range. This will support isolated severe-hail potential with the best-organized cells. ...Edwards/Leitman.. 11/19/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .