Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 07 2023 12:54:12 ACUS01 KWNS 071254 SWODY1 SPC AC 071252 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0652 AM CST Sat Jan 07 2023 Valid 071300Z - 081200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ON THE MIDDLE/UPPER TEXAS COASTAL PLAIN... ....SUMMARY... Isolated, marginally severe hail and/or thunderstorm gusts are possible this afternoon and evening on the middle/upper Texas Coastal Plain. ....Synopsis... In mid/upper levels, a progressive, shortwave-dominated upper-air pattern is expected over the CONUS. One shortwave trough -- with an intermittently closed/weak cyclone apparent in moisture-channel imagery over southeastern NE -- extends southwestward to northeastern NM. This feature is expected to shift eastward to the mid Mississippi Valley by 12Z tomorrow. A smaller, southern-stream perturbation -- initially evident over coastal Sonora -- should move east-northeastward across northwestern MX and far west TX through tonight, reaching the Permian Basin and lower Pecos Valley regions by the end of the period. Upstream, a series of small vorticity lobes will move ashore over central/northern CA and OR today. This will occur in advance of a stronger shortwave trough -- now rapidly approaching 140W and forecast to reach the central/northern CA Coast very near 12Z tomorrow. At the surface, 11Z analysis showed a low over eastern OK, with cold front southwestward across north-central TX and the lower Pecos Valley. By 00Z, the low should move eastward to eastern AR, with cold front southwestward over northeast and south-central TX to northern Coahuila. By 12Z, the low should be near BNA, with cold front to near JAN, LCH, just off the upper TX Coast, to near CRP and LRD. ....Mid/upper TX Coastal Plain... Scattered thunderstorms are expected to develop along and behind the front today and tonight, with at least isolated thunderstorms possible ahead of it. Variably organized multicellular modes are expected, with isolated damaging gusts possible in the frontal/ prefrontal convection, where boundary-layer instability will be greatest. Isolated severe hail is possible on either side of the front. Within an immature yet still moist return-flow regime, the prefrontal boundary layer across the TX Coastal Plain will be characterized by mid-upper 60s F surface dewpoints. Modified 12Z CRP/LCH RAOBs and model-forecast soundings indicate steady erosion of a 750-850-mb stable/capping layer at the base of a weak EML, as diurnal heating and moist advection continues. This will support some warm-sector convection, which may mature to strong or marginal severe intensity before interacting with the front. Frontal lift, impinging on the destabilized boundary layer, should support additional development, as well as a favorable unstable, elevated inflow layer some 50-75 nm behind the front. The bulk of large-scale DCVA-related ascent aloft will remain well behind the front, and low-level flow should remain relatively weak, keeping hodographs small for surface-based convection. Lack of stronger midlevel winds should keep effective-shear magnitudes under 30 kt in most of the area. These factors will limit overall event organization, and densely clustered/messy storm modes may evolve rather quickly while being undercut by the front. Still, warm advection related to both mid/upper perturbations and favorable upper-level/ventilating winds will spread across the area, amidst deep buoyancy and weak CINH, supporting at least a few organized multicells offering pulse wind/hail potential. ...Edwards/Broyles.. 01/07/2023 $$ = = = 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) .