Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Feb 21 2023 00:57:41 ACUS01 KWNS 210057 SWODY1 SPC AC 210056 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0656 PM CST Mon Feb 20 2023 Valid 210100Z - 211200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... The risk for thunderstorms appears likely to remain generally low across much of the U.S. through early Tuesday. ....01Z Update... The main branch of westerlies is undergoing considerable amplification across the northern mid-latitude Pacific. By late tonight, this will include a vigorous short wave trough digging into the Pacific Northwest, around the northern periphery of a blocking mid-level high initially centered over the southern mid-latitude Pacific. While the high tends to gradually reform to the west-northwest, positively tilted mid-level troughing to its southeast is forecast to slowly begin accelerating out of the subtropical eastern Pacific. Eastward progression will be impeded by a persistent prominent subtropical ridge becoming centered across the Caribbean, but a compact and still vigorous embedded cyclonic circulation may begin pivoting east-northeastward by late tonight, after bottoming out to the west of northern Baja California Sur. Downstream of the trough digging into the Northwest, low amplitude mid-level ridging will build across the northern Rockies into the northern Great Plains. The leading edge of broad mid-level troughing, farther east, is forecast to continue spreading offshore of the northern Atlantic Seaboard, while the trailing edge shifts east of the Upper Mississippi Valley. This latter regime includes at least a couple of notable perturbations: one accelerating into the Canadian Maritimes, and another digging across the Upper Midwest into Great Lakes region. A more subtle perturbation, in between, appears to be progressing through the Ohio Valley. ....Ohio Valley... While forecast soundings, and the 21/00Z sounding from Wilmington, OH, suggest that the environment is rather marginal for thunderstorm development, low-topped convection capable of producing lightning has developed in a narrow pre-cold frontal corridor across the middle into upper Ohio Valley. It appears that this activity probably has been supported by weak boundary-layer destabilization aided by daytime heating, and it seems likely to diminish during the 02-03Z time frame, if not before, with further nocturnal cooling. ....Northern Gulf States... Somewhat better/deeper low-level moisture has remained capped by warm layers aloft as it spread northeastward and eastward through the day. However, latest model output continues to suggest that some suppression of mid-level ridging may weaken inhibition sufficiently to support scattered weak thunderstorms in a corridor across parts of southern Tennessee and northern Mississippi, Alabama and Georgia by the 03-06Z time frame. ...Kerr.. 02/21/2023 $$ = = = 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) .