Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 21 2024 06:01:11 ACUS01 KWNS 210601 SWODY1 SPC AC 210559 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Thu Mar 21 2024 Valid 211200Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF TEXAS AND FAR SOUTHWEST LOUISIANA... ....SUMMARY... Isolated severe thunderstorms producing large hail and strong wind gusts are possible from parts of far southwest Louisiana and the Texas Coastal Plain northwestward into central and north Texas. ....Southern Plains/Sabine River Valley... An upper-level trough will move eastward across northern Mexico today, as an associated surface low develops and moves northeastward along the Texas coast. A moist airmass, with surface dewpoints in the mid to upper 60s F, will be located along the lower to middle Texas Coast. The moist axis will extend northwestward into central and north Texas. Moderate instability appears most likely to develop from the lower to middle Texas coast inland about 50 statute miles. However, weak instability sufficient for strong updrafts should develop across most of the moist airmass by afternoon. Thunderstorms will likely be ongoing at the start of the period, with a cluster of convection moving northeastward from near Corpus Christi to the Houston vicinity during the morning and early afternoon. Additional storms are forecast to develop further northwest along and near the moist axis during the afternoon across parts central and north Texas. A second round of storms may impact the Texas Coastal Plain during the evening. Ahead of the approaching system, deep-layer shear is expected to increase across the Texas Coastal Plain during the day. RAP forecast soundings near Victoria increase 0-6 km shear from 35 knots at 12Z to near 50 knots by 20Z. This increase in deep-layer shear will likely correspond to an increase in the potential for supercells. The thermodynamic environment over the Texas Coastal Plain is forecast to be favorable for large hail, with 700-500 mb lapse rates in the 7 to 7.5 C/Km range, and 500 mb temperatures around -13 to -15C. Supercells that form will have the greatest threat for large hail. The wind-damage threat is more uncertain, and should depend upon the dominant storm mode. In spite of a low-level temperature inversion evident in the forecast soundings, isolated wind damage may occur, especially if a more persistent line segment can become organized. A marginal tornado threat could also develop if a supercell becomes dominant with that threat extending into far southwest Louisiana, where low-level shear will be strong in the afternoon. Further northwest into parts of central and north Texas, weak destabilization is expected by afternoon as surface temperatures warm. An upper-level low will move into northwest Texas, where a cold pocket aloft will create steep mid-level lapse rates. As scattered thunderstorms increase in coverage during the afternoon, hail will be possible within the stronger cores. The threat is expected to be strongly tied with surface heating. ...Broyles/Flournoy.. 03/21/2024 $$ = = = 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) .