Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Fri Dec 01 2023 09:01:00 ACUS01 KWNS 011244 SWODY1 SPC AC 011243 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0643 AM CST Fri Dec 01 2023 Valid 011300Z - 021200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF COASTAL SOUTHEAST TEXAS TO THE WESTERN FLORIDA PANHANDLE... ....SUMMARY... Thunderstorms with marginal tornado and/or wind potential are possible from parts of coastal southeast Texas to the western Florida Panhandle. ....Synopsis... In mid/upper levels, a series of shortwaves will traverse broader, progressive troughing over the western CONUS. As that occurs, an initially well-developed, negatively tilted shortwave trough over western IL will eject northeastward and weaken considerably, reaching parts of PA/NY by 00Z. A weaker, convectively augmented perturbation and associated vorticity lobe -- evident in moisture- channel and composited radar imagery over southern portions of MS/LA -- will also eject away from the Gulf Coast region, likely moving offshore from the Carolinas and GA around 00Z. In response to these developments, weak height rises are expected over the western/ central Gulf Coast region. A surface low related to the leading shortwave trough was analyzed at 11Z over central MO, with cold front across southwestern MO, the OK/AR border region, east TX, and near the lower/middle TX Coast. By 00Z, the low should be weakening and located near the IL/IN border, having been rapidly outrun by the mid/upper wave. The cold front should extend south-southwestward down the lower Ohio and lower Mississippi Valleys to the LCH vicinity, temporarily stalling or drifting southeastward near the upper TX Coast and just offshore the remainder of the TX Coast through the day. A weak frontal-wave low may develop over southwestern/central LA this evening, then ripple northeastward along the front. By 12Z, the younger low should be over central/east-central MS -- roughly between JAN-MEI -- with cold front near BTR and LFT, to shelf waters offshore from the TX Coast. ....Gulf Coastal Plain, Lower Delta... A prefrontal, southwest/northeast-oriented band of thunderstorms is ongoing from the LA Coast south-southwest of LFT across I-12 between BTR-SIL, becoming more diffuse into southeastern MS. Activity within the band should continue moving quickly northeastward, outpacing a marine/warm front initially apparent over the Lake Pontchartrain and BTR areas. However, embedded cells in the Atchafalaya River region and southwestward should remain in the slowly northeastward-expanding warm sector for at least a few more hours, potentially accessing surface-based effective-inflow parcels. As a combination of theta-e advection and muted diurnal heating strengthen low-level lapse rates/buoyancy somewhat, large-scale support will weaken, as will winds near the top of the boundary layer, shrinking hodographs. While deep shear will remain favorable into afternoon, the other counterbalancing factors, amid a training convective mode, suggest embedded supercell potential, but with severe threat being too uncertain and conditional for more than marginal probabilities. Another round of strong to isolated/embedded severe thunderstorms is possible tonight along or just ahead of the cold front. Somewhat rejuvenated but still marginal severe gust/tornado potential is expected overnight as: 1. The prefrontal boundary from the early convection retreats diffusely inland over LA/MS/AL, 2. Strengthening gradient flow aloft leads to greater deep shear, and 3. The LLJ increases again, lengthening and somewhat enlarging hodographs. Offsetting processes will include weak low/middle-level lapse rates (though with upper 60s/low-70s surface dewpoints, MLCAPE may remain near 1000 J/kg into much of the night), as well as weak near-surface winds and the presence of generally messy convective modes. ...Edwards/Kerr.. 12/01/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .