Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 12 2025 19:55:37 ACUS01 KWNS 121955 SWODY1 SPC AC 121953 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Wed Mar 12 2025 Valid 122000Z - 131200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF NORTHEAST TEXAS/SOUTHEAST OKLAHOMA INTO ARKANSAS AND NORTHWEST LOUISIANA... ....SUMMARY... Scattered severe thunderstorms will be possible from parts of north Texas and southeast Oklahoma into the ArkLaTex late this afternoon and evening. Large to very large hail and severe gusts should be the primary hazards. ....20z Update... The prior outlook remains valid with minor changes including: adjustment of the MRGL/SLGT areas farther south and trimming of thunder eastward near the dryline across North TX. ....ArkLaTex and southeastern OK... A compact shortwave trough, evident on moisture-channel/visible imagery, over parts of west-central TX is forecast to continue eastward this afternoon and into the early evening hours. Ascent and cooler mid-level temperatures are overspreading a moistening air mass across parts of eastern TX/OK and AR/LA, contributing to moderate destabilization. Capping should remain firm through most of the afternoon, but robust heating and increasing ascent over the dryline/surface trough should allow for isolated thunderstorm initiation late this afternoon/early evening from southeastern OK, to along and south of I-20. Low freezing levels, steep mid-level lapse rates (8.5-9 C/km) and 35-50 kt of effective shear will favor supercells with large to very large hail. Low-level shear is not overly robust, and given the high LCLs (~1500-1700 m AGL) the tornado threat appears lower. However a tornado or two will remain possible, especially across the southernmost risk areas where dewpoints in the low 60s F are more likely. Some CAM guidance shows upscale growth into a small bowing segment/cluster may occur over east TX through the ArkLaTex tonight. Should this occur, a risk for damaging winds may continue over the lower MS Valley overnight. See the prior outlook for more info. ...Lyons.. 03/12/2025 ..PREV DISCUSSION... /ISSUED 1128 AM CDT Wed Mar 12 2025/ ....North Texas/Southeast Oklahoma into the Lower Mississippi Valley... A shortwave trough with an attendant 70-90+ kt west-southwesterly mid-level jet will advance eastward across the southern Plains today. A related surface low should gradually consolidate over OK and likewise develop slowly eastward through the period. Shallow low-level moisture will continue to stream northward ahead of a dryline that will mix eastward across parts of central TX through late this afternoon, with surface dewpoints generally remaining in the mid 50s to low 60s. A pronounced cap evident on the 12Z FWD sounding will be slow to erode, and this will likely inhibit robust thunderstorms from developing until at least late afternoon (21Z or later). Even so, mid-level temperatures will cool through the day as the shortwave trough approaches, and steep lapse rates aloft in combination with daytime heating will also aid in the development of around 1000-1750 J/kg of MLCAPE across northeast TX/southeast OK ahead of the dryline. While low-level winds are expected to remain fairly modest, strengthening mid-level winds and related deep-layer shear should support organized convection. While there is still some uncertainty regarding how warm/moist the boundary layer will become through heating, it seems likely that attempts at robust convective initiation will occur by late afternoon/early evening across north-central TX into southeast OK as convergence increases along/near the dryline. Any convection that can develop and persist will likely become supercellular and pose a threat for large to very large hail (perhaps up to 2-2.5 inch diameter). Amalgamation/upscale growth may occur with this activity through the evening across parts of the ArkLaTex, with some risk for damaging winds with any sustained cluster continuing eastward over the lower MS Valley overnight. The tornado threat remains less clear, with modest/shallow low-level moisture and generally weak low-level winds potentially limiting factors. Still, a chance for a tornado or two may exist with any sustained supercell this evening as a southwesterly low-level jet gradually strengthens, especially in the ArkLaTex region. ....Coastal Southern California... Short-term guidance shows a low-topped band of convection will move across parts of coastal southern CA in advance of an approaching mid-level trough over the eastern Pacific. While a strong gust cannot be ruled out with this activity, the overall thermodynamic environment appears too limited for low severe probabilities. $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .