Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 21 2023 12:39:20 ACUS01 KWNS 211239 SWODY1 SPC AC 211237 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0737 AM CDT Tue Mar 21 2023 Valid 211300Z - 221200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... Severe thunderstorms are not expected today. ....Synopsis/Discussion... In mid/upper levels, an initially nearly zonal pattern across most of the CONUS -- with minor/embedded shortwaves -- will amplify through the period. This will be related to a well-defined, synoptic-scale cyclone -- located initially over the northeastern Pacific, west of CA. The 500-mb low should pivot eastward across the SFO area around 00Z, then weaken and move northeastward toward southwestern ID by the end of the period. However, a substantial, positively tilted trough still will be left to the southwest of the low, extending across central/western NV, the Sierra Nevada, south-central to coastal southern CA, then for at least another 600-700 nm southwestward over Pacific waters. A broad area of episodic, isolated thunderstorm potential will exist ahead of the cyclone and trough, across much of CA, the Great Basin and the northern Colorado Plateau. Cold air aloft and steep midlevel lapse rates will overlie sufficient low/middle-level moisture for favorably vertically positioned CAPE to develop. Just ahead of the low aloft, forecast soundings show enough midlevel cooling to support 100-400 J/kg MLCAPE (despite cool surface temperatures) and veering winds with height, with well-curved but small hodographs. A brief supercell or two with small hail and strong gusts may occur over the San Joaquin or southernmost Sacramento Valley, especially if low-level flow is stronger than currently progged. Farther east, a shortwave trough -- now evident in moisture-channel imagery over southwestern KS and northwestern OK -- is expected to weaken gradually as it moves east-northeastward to IL by 00Z. The perturbation should reach northern VA, western MD and southern PA by 12Z. A warm to quasistationary front was drawn at 11Z from a weak low over southeastern CO, across north-central KS, southeastern NE, central IA, and southern WI. A cyclone should form along this boundary overnight, over western MN, in response to an approaching northern-stream shortwave perturbation now manifest as a small cyclone over the ID/WY border. Isolated thunder is possible for a few more hours within a broad area of precip already apparent on either side of the surface front, and rooted in an elevated layer of weak buoyancy, over parts of OK, southeastern KS, MO, and AR. This activity is being supported by a broad plume of low-level warm/moist advection above the relatively stable boundary layer, with some DCVA/lift preceding the leading/southern shortwave trough as well. ...Edwards/Dean.. 03/21/2023 $$ = = = 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) .