Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 18 2023 09:02:35 ACUS48 KWNS 180902 SWOD48 SPC AC 180900 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Thu May 18 2023 Valid 211200Z - 261200Z ....DISCUSSION... Medium-range models are in general agreement regarding evolution of the synoptic pattern over the U.S. through the medium range. As an upper trough progresses across the eastern U.S. early next week, a second trough is forecast to expand gradually over the West, and linger there through the period. Downstream, in the wake of the departing eastern trough, ridging will become established. As the eastern trough progresses, a surface cold front will continue moving eastward across the western Atlantic, and southward into the Gulf, with a stout area of high pressure expanding across the eastern two-thirds of the country in the wake of the front. This area of high pressure will therefore largely keep higher theta-e air confined to the far southern U.S. -- i.e. Texas and Florida -- through the period. Greatest severe-weather potential will likely reside over the High Plains, evolving Day 5 to 6, and then lingering there with a noted diurnal (afternoon/evening) peak. This will occur as modest moisture leaks northward across the High Plains on southerly flow on the back side of the broad area of surface high pressure. With weak westerly/southwesterly flow aloft across the Rockies, a lee trough will likely be maintained. As such, subtle disturbances in the flow aloft will likely focus favored areas along the lee trough for afternoon convective development, that would then tend to progress southeastward given the low-level southeasterly flow regime. With elevated mixed-layer air/steep lapse rates in place, modest instability, and a wind profile veering from southeasterly to southwesterly with height and a nocturnal low-level jet evolving each evening, it would appear that clusters of strong/severe storms will be possible each afternoon which would then spread southeastward toward lower elevations. With that said, picking out areas/days where risk may be greater than the background low-level threat is difficult, given the subtle forcing, and thus no risk areas will be included at this time. ...Goss.. 05/18/2023 = = = 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) .