Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 24 2023 12:56:49 ACUS01 KWNS 241256 SWODY1 SPC AC 241255 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Tue Jan 24 2023 Valid 241300Z - 251200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE TEXAS COAST TO THE WESTERN FLORIDA PANHANDLE... ....SUMMARY... Severe thunderstorm winds and a threat of tornadoes are expected today near the middle/upper Texas Coast, then eastward tonight across coastal areas of Louisiana, Mississippi, Alabama, and the western Florida Panhandle. ....Synopsis... The main mid/upper-level feature for this forecast will be a synoptic-scale trough attendant to a compact cyclone now centered over the LRU/ELP vicinity. The 500-mb low is forecast to move east-northeastward to near DFW by 00Z, with trough positively tilted southwestward across central/southwest TX and northern MX. By 12Z, the mid/upper low should reach the Mississippi River in the STL-CGI region, with the trough across the Ozarks and central TX to Coahuila. As this occurs, a broad belt of locally very intense cyclonic flow aloft will extend from the Great Basin and northern MX across the western/central Gulf Coast region, shifting eastward along the coast as the main vorticity lobe ejects across eastern OK, AR and southern MO tonight. At the surface, 11Z analysis showed a low over northern Coahuila, with cold front roughly southward across northeastern MX, and warm front eastward over deep south TX (just north of the lower Rio Grande Valley) and the northwestern to central Gulf. The low should move/redevelop northeastward to a position in the CLL/IAH area by 18Z today, to west-central LA by 00Z, then outpacing the inland advance of the warm sector and moving across the Mid-South to near PAH by the end of the period. The trailing cold front should extend near a LCH-BRO line by 00Z, then from eastern AL across the western FL Panhandle to the southwestern Gulf by 12Z tomorrow. The warm front should move to very near, or just inland from, the immediate upper TX and LA coastlines through this evening, then diffusely somewhat further inland across MS/AL/FL Panhandle tonight. ....Gulf Coast... A few supercells may develop over the Gulf throughout the period and move ashore in the prefrontal/warm sector, on either side of the surface warm front. Any such cells interacting with the front over land, or in the warm sector, will be in a favorable buoyancy/shear parameter space for a tornado threat, and large hail will be possible from relatively discrete cells over the western Gulf Coastal plain where deep-layer lapse rates will be greatest. The bulk of convection, however, is expected to occur as part of a quasi-linear convective system (QLCS) organizing from midday into afternoon, perhaps evolving from previously elevated, midmorning to midday convection over south-central TX. As this activity shifts eastward over the middle/upper TX Coastal Plain, and begins to interact with the destabilizing warm-frontal zone and warm sector, it should intensify to severe levels, offering mainly damaging wind and a few tornadoes with embedded bow/LEWP features and mesovortices. Increasingly buoyant air is expected in the boundary layer the QLCS will encounter near the coast this afternoon and evening, with upper 60s to low 70s F surface dewpoints common along and south of the front. This air mass will underlie seasonally steep midlevel lapse rates over the western parts of the outlook area, thanks largely to a modest EML (apparent in the 12Z BRO RAOB, but with only a weak basal stable layer) originating over the Mexican plateau. MLCAPE of 1000-1500 J/kg is expected near the mid/upper TX Coast and is possible a short distance from the Gulf into southern LA. Mass response to the cyclone/trough aloft will foster strong deep-layer winds, with favorable deep shear and low-level hodographs. The latter will become large area-wide, shifting eastward ahead of the QLCS, with effective SRH of 250-400 J/kg being common near the warm front. An intense (50-70-kt) LLJ near the coast will expand the hodograph near the warm front enough to support locally higher effective SRH as well. The direct influence of the EML will wane gradually with eastward extent as the QLCS crosses LA/MS/AL to the western FL Panhandle; however, boundary-layer theta-e near the coast should be enough to maintain a deep CAPE profile. In fact, low-level warm advection and moisture transport should enable the QLCS to expand inland in the low-level warm-frontal zone, which will be characterized by gradually stabilizing near-surface air poleward. That stabilization will render severe-wind and tornado potential more conditional with inland extent, though isolated events are possible as far inland as central parts of MS/AL. ...Edwards/Goss.. 01/24/2023 $$ = = = 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) .