Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Apr 12 2023 12:40:59 ACUS01 KWNS 121240 SWODY1 SPC AC 121239 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Wed Apr 12 2023 Valid 121300Z - 131200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG PARTS OF THE NORTHEASTERN GULF COAST... ....SUMMARY... Isolated damaging winds or a tornado are possible along parts of the northeastern Gulf Coast late tonight into tomorrow morning. ....Synopsis... In mid/upper levels, a progressive, synoptic-scale trough was located near the West Coast, with embedded low just offshore from AST. Through the period, the low should move inland to southwestern ID near BOI, with trough north-northeastward across the northern Rockies and south-southwestward over southern CA and the Pacific west of Baja. As this occurs, the ridging around the north side of a cyclone over the LA Coast should begin to erode, but not enough to remove the blocky nature of the pattern before the end of this period. The Gulf Coast 500-mb low is expected to deepen slowly and drift erratically eastward along the LA coastline through the period, before ejecting inland on day 2. In response, a weak frontal-wave low -- analyzed at 11Z over the central Gulf east of NOAA buoy 42001 -- will intensify substantially and move roughly north-northwestward toward extreme southeastern LA or the MS Coast, moving inland near the end of the period. By 12Z, the low should be in the MSY-GPT corridor, with warm front eastward along the coast to the FL Panhandle, then across parts of central or south FL. With eastward extent across FL, the warm front's poleward pace will depend on strength and persistence of overland, convective reinforcement of baroclinicity to its north. ....Northeastern Gulf Coast... Scattered to locally numerous thunderstorms are forecast in a zone of deep, persistent low-level convergence east through north of the surface low. Some of this activity, especially close to the coast, may pose a brief tornado or damaging-gust threat, mainly late tonight during the last few hours of the period. The threat then will continue and expand inland after 12Z -- refer to the day-2 outlook for coverage of that process. This day-1 cycle, the outlook only needed minor adjustment on the west end to pull it out of the immediate area of the low's track (where near-surface wind speeds will be somewhat weaker by the time suitable SBCAPE arrives), also conforming closely to the start of the day-2 outlook. As the low-level cyclone intensifies and approaches the coast overnight, strongly difluent flow in the 500-250-mb layer will spread across the outlook area. The easterly LLJ axis in the cyclone's middle/outer northeastern quadrant is expected to strengthen to 45-55 kt. That axis should precede the surface warm front inland. A narrow corridor of overlap should develop between richly moist, surface-based effective-inflow parcels nearer the front, and the southern rim of the LLJ, where 25-40-kt east- southeast flow still should be present. Forecast soundings accordingly yield enlarged, loopy low-level hodographs with around 100-150 J/kg SRH in the lowest 1/2 km. Though deep shear will be modest (e.g., 25-30-kt effective-shear vectors), some supercell characteristics are possible within a broader plume or band of convection, along with low LCL, and increasing theta-e with time. East of about MOB to western Apalachee Bay, and roughly south of I-10, MLCAPE may reach 500-1000 J/kg along the warm front by 12Z. ...Edwards/Smith.. 04/12/2023 $$ = = = 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) .