Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 05 2025 10:00:44 ACUS48 KWNS 051000 SWOD48 SPC AC 050959 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CST Wed Mar 05 2025 Valid 081200Z - 131200Z ....DISCUSSION... Cyclonic mid-level flow characterized by seasonably low heights appears likely to linger across much of eastern Canada and the U.S. Great Lakes vicinity through Northeast into this weekend, as broad ridging builds in the subtropical and southern mid-latitudes. This latter development is forecast to occur downstream of a significant short wave trough emanating from the mid-latitude Pacific, with an embedded closed low forming across the Southwest into southern Rockies by 12Z Saturday. Medium-range guidance indicates that this perturbation will remain progressive, as a significant upstream short wave trough rapidly progresses across the southern mid-latitude eastern Pacific, toward the southern California coast over the weekend. It still appears that the lead short wave will become increasingly sheared within a confluent regime east of the Rockies through the Atlantic Seaboard. The ECENS/ECMWF-based output and GEFS/GFS-based output remain varied concerning how fast and the extent to which this occurs, with the latter guidance still indicating a bit more notable surface wave development along a frontal zone across the Gulf coast region. There does appear a consensus that Gulf boundary-layer modification may support a notable plume of returning low-level moisture ahead of the mid-level wave, across Gulf coastal areas into and along the frontal zone. Beneath initially steep lower/mid-tropospheric lapse rates, guidance indicates that this will support modest potential instability in the presence of strong deep-layer shear. This could lead to a corridor of vigorous thunderstorm development on Saturday, with stronger convection possibly becoming supportive of severe hail and perhaps locally strong surface gusts. It remains unclear whether this will setup near immediate upper Texas through north central Gulf coastal areas, or as far north as the Ark-La-Tex through central/northern Mississippi and Alabama. Stronger frontal wave development would probably support more substantive and further inland severe weather potential, which could spread across parts of the southern Atlantic Seaboard on Sunday. Due to the low predictability at this time, and the somewhat marginal nature of the severe threat, severe weather probabilities are being maintained at less than 15 percent. Into early next week and beyond, as the lower heights shift out of the Northeast, a series of amplified, but progressive waves within the westerlies emanating from the Pacific may contribute to periodic, potentially significant cyclogenesis to the lee of the Rockies, However, in the wake of the lower latitude weekend trough, low-level moisture return off the Gulf may be initially limited. ...Kerr.. 03/05/2025 = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .