Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 20 2023 12:57:05 ACUS01 KWNS 201257 SWODY1 SPC AC 201255 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Fri Jan 20 2023 Valid 201300Z - 211200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... Organized severe thunderstorms appear unlikely through tonight. ....Synopsis/Discussion... Moisture-channel imagery indicates a broad mid/upper-level cyclone covering much of the Great Basin region, with its center skewed to the southern part of the gyre over northwestern AZ. Confluent flow aloft was apparent downstream from a ridge, over the Great Plains to the Mississippi Valley. A zonally elongated 500-mb cyclone over southern ON should shift eastward over New England by late afternoon or early evening, moving offshore toward waters south of Newfoundland by 12Z tomorrow. Meanwhile, the Great Basin cyclone will move roughly eastward along the AZ/UT and CO/NM borders, across the Four Corners today and over the San Juans this evening. The 500-mb low should reach the western OK Panhandle by 12Z tomorrow, embedded in a strong, open- wave trough from the central High Plains across northeastern through southwestern NM and southern AZ. As this occurs, associated midlevel DCVA/lift/cooling and steepening low/midlevel lapse rates -- in the presence of suitable low/middle-level moisture -- should result in isolated, streaky lightning potential within the associated, roughly comma-shaped precip field. The comma tail will consist of convection aided by lift along a low-level cold front that, by 12Z, should arc southeast then southwest from the cold-core region of the cyclone, reaching the OK/TX Panhandles. Time series of forecast soundings reasonably suggest that weak low-level theta-e will limit MUCAPE to less than about 300 J/kg. However, buoyancy may be well-distributed vertically into icing layers suitable for lightning production, with the most vigorous cells that suffer the least dry entrainment. Mass response to the eastward-moving mid/upper trough will boost a broad low-level warm-advection/moisture-transport regime across the west-central Gulf Coast region. Associated moistening and low/ middle-level destabilization, increasing elevated buoyancy, and isentropic ascent to LFC, should foster increasing convective coverage this evening and overnight across portions of the TX Coastal Plain and southwestern LA, spreading into the lower Delta region by the end of the period. 200-800 J/kg MUCAPE, rooted in the 700-850-mb layer and extending into upper levels, will support thunderstorm potential. A wide spectrum of effective shear is possible, with vector magnitudes of 30-60 kt depending strongly on thickness of buoyant layer (which regulates depth through which the values are computed). A few semi-organized cells may produce small hail survivable through a deep, near-surface stable layer. However, severe hail/wind potential appears too low and conditional for an outlook area. ...Edwards/Dean.. 01/20/2023 $$ = = = 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) .