Subj : DAY1SVR: Marginal Risk S To : All From : Mike Powell Date : Wed Mar 20 2024 07:55:00 ACUS01 KWNS 201239 SWODY1 SPC AC 201238 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Wed Mar 20 2024 Valid 201300Z - 211200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS WESTERN OK/NORTHWEST TX...AND EARLY THURSDAY MORNING NEAR THE TX COAST... ....SUMMARY... Isolated, marginally severe storms will be possible this afternoon/evening across parts of western Oklahoma and northwest Texas. Isolated large hail will be possible early Thursday morning near the Texas coast. ....Western OK/TX Panhandle this afternoon/evening... A midlevel shortwave trough will begin to move eastward from AZ/NM toward west TX by tonight, with associated downstream cyclogenesis occurring today across eastern NM and the TX Panhandle. Low-level moisture return will be limited in the warm sector, with boundary-layer dewpoints ranging from 40-45 F as surface temperatures warm into the 70s this afternoon along a surface trough/front across western OK and the eastern TX Panhandle. Steepening low-midlevel lapse rates and cool midlevel temperatures will support weak buoyancy, and weak ascent along the boundaries could result in a few storms with the potential to produce marginally severe hail and strong outflow gusts. There is also a low probability of a non-mesocyclone tornado with developing updrafts along the slow-moving front in northwest OK later this afternoon, given steep low-level lapse rates/vertical vorticity along the front. ....South central TX to the coastal plain late tonight... Low-level moisture return will occur in earnest by tonight as a maritime tropical air mass spreads northward from the Bay of Campeche (along the prior stalled front) to the TX coast. Near the end of the period, destabilization will become sufficient for elevated thunderstorm development in the warm advection zone atop a diffuse coastal front. MUCAPE could reach 1000-1500 J/kg as moisture increase below midlevel lapse rates of 7.5-8 C/km, in an environment with sufficiently long hodographs (and some low-level curvature) for a conditional supercell/large hail threat mainly 09-12z. ....Southern New England this afternoon... A deepening midlevel trough will move from ON to New England, as an associated cold front moves across New England later today and cyclogenesis occurs tonight near the ME coast. Moisture/buoyancy will be scant at best ahead of the cold front across southern New England, where some shallow/forced convection may occur along the cold front this afternoon. The convection could be associated with a few strong gusts, but the potential for convectively driven severe gusts appears too low to warrant introduction of an outlook area. ...Thompson/Grams.. 03/20/2024 $$ --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .