Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 19 2022 12:46:24 ACUS01 KWNS 191246 SWODY1 SPC AC 191244 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0644 AM CST Mon Dec 19 2022 Valid 191300Z - 201200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... Thunderstorms should develop and spread eastward across the Gulf Coastal Plain from south Texas to near Mobile. Though small hail is possible, organized severe weather still appears unlikely over land. ....Synopsis/Discussion... A progressive, generally low-amplitude mid/upper-tropospheric pattern is apparent over the CONUS for the time being, as an interlude between two phases of high-amplitude synoptic forcing a few days ago and later this week. The main feature of relevance for this forecast is a southern-stream shortwave trough -- apparent in moisture-channel imagery from the DDC area southwestward across eastern/southern NM to central Baja. The northern part of this trough will break eastward and weaken rapidly today, while the southern part crosses NM and northwest MX. By 00z, the remaining troughing should extend across northwest and far west TX and Chihuahua. By 12Z, the trough should extend from western AR across north-central TX to the Big Bend region. At the surface, 11Z analysis showed a frontal-wave low over the northwestern Gulf coastal waters very near the central/southern part of Padre Island, with warm front east-southeastward across the central Gulf to near the northwestern coast of Cuba. Today the low is expected to move northward, northeastward then eastward, roughly parallel to the coast but slightly offshore, while the western segment of the warm front shifts northward in step with the latitudinal progress of the low. ....Western/central Gulf Coastal Plain... Isolated to widely scattered thunderstorms have developed in a broad plume of low-level warm advection and moisture transport, elevated above a relatively stable boundary layer, across parts of south TX and southwestern LA. As the shortwave trough proceeds eastward, this warm-advection conveyor will shift/spread across more of the LA/MS/AL coastal plain through tonight, enabling thunderstorms as increasingly moist parcels isentropically rise to an LFC. The forecast motion of the low and warm front should keep the most thermodynamically favorable parts of the warm sector offshore, over shelf and open Gulf waters, though a narrow sliver of nearly surface-based effective-inflow parcels may brush across the middle TX Coast today and southernmost parts of the LA Coast overnight. Abundant inland precip into an antecedent, stable, near-surface layer will reinforce baroclinicity and further impede the warm front's poleward progress. As such, the most intense convection (including a threat for surface-based supercells and bowing convective segments) will remain offshore, as a concern mainly for maritime and platform interests. Forecast soundings show up to about 1500 J/kg MUCAPE reaching the middle/upper TX Coast from midday into afternoon as the low passes just to the south, amidst 50-60-kt effective-shear magnitudes. As such, elevated strong thunderstorms with hail are possible, though the hail threat will be tempered by potentially messy storm mode and lack of more-robust lapse rates aloft. Buoyancy will weaken with northward/inland extent from there, while mid/upper-level lapse rates weaken eastward in the convective environment overnight. ...Edwards/Kerr.. 12/19/2022 $$ = = = 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) .