Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 25 2023 08:23:39 ACUS48 KWNS 250823 SWOD48 SPC AC 250821 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0321 AM CDT Sat Mar 25 2023 Valid 281200Z - 021200Z ....DISCUSSION... Severe potential will be low on Days 4-5/Tue-Wed. A low-amplitude upper trough will pivot eastward across the eastern U.S. during this time, while an upper ridge builds over the Plains ahead of a western trough. At the surface, a cold front draped across the Gulf Coast/Southeast vicinity will drop south into northern Gulf and offshore the Atlantic coast. Surface high pressure overspreading much of the central and eastern U.S. will maintain a stable airmass through Wednesday. On Day 6/Thu, the western upper trough is expected to shift east toward the southern Rockies, displacing the upper ridge over the Plains to the east of the MS River. In response to height falls, lee cyclogenesis will occur, and increasing southerly low-level flow over the southern Plains will transport Gulf moisture northward across TX, OK and parts of KS. Strong to severe thunderstorms along a dryline appear possible across parts of TX/OK Thursday afternoon/evening. Additional severe thunderstorm activity may develop as far north as central/eastern KS as a cold front develops southeast. Differences in the timing of the ejecting upper trough (GFS-based guidance is more progressive/faster than ECMWF-based guidance, and the Canadian is somewhere between the two). As a result, not much change has been made to the 15% severe delineation for Thursday. This also lends to uncertainty regarding severe potential for Day 7/Fri. If a slower evolution prevails, severe potential could persist across parts of the Plains into the Mid/Lower MS Valley. If a fast progression occurs, some severe potential may develop across the Mid-MS Valley early in the day, but would likely quickly diminish with eastward extent. Given this uncertainty, severe probabilities will not be introduced for Day 7/Fri. By Day 8/Sat, regardless of a faster or slower upper trough progression, stronger large-scale ascent and shear will become displaced from better low-level moisture, limiting severe potential. ...Leitman.. 03/25/2023 = = = 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) .