Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 29 2025 09:04:22 ACUS48 KWNS 290903 SWOD48 SPC AC 290902 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Sat Mar 29 2025 Valid 011200Z - 061200Z ....DISCUSSION... Medium-range models appear to be in fairly good agreement through much of the medium-range period, with respect to large-scale pattern evolution/placement of the main synoptic-scale features. One primary difference between the GFS and ECMWF at this time is that the EC is more highly amplified with the upper pattern through the period, and thus -- in general -- depicting stronger surface features and greater flow aloft/wind shear. One result of the higher amplitude of the ECMWF manifests Day 4/Tuesday April 1. As the eastern U.S. trough moves off the Atlantic Coast, and the cold front stalls over the northern Gulf of America early, northward return of this boundary as a warm front is forecast over the southern and eventually the central Plains. Central High Plains cyclogenesis is expected along this front as it shifts northward. However, given the more amplified nature of western troughing within the ECMWF, a much stronger surface cyclone is progged by the EC as compared to the GFS (984 mb vs. 991 mb respectively). The result is much stronger low-level theta-e advection across the central/southern Plains depicted by the EC, driving a much more rapid northward advance of the warm front. Both models suggest after-dark convective development, but where the GFS depicts weaker, elevated CAPE across Kansas, the EC's more robust, potentially near surface-based CAPE suggests greater, more widespread severe potential than the GFS. At this time, a small 15% area will be introduced, centered over the mid Missouri Valley area, mainly for the potential for hail with stronger storms. Later refinements of the risk area will likely be required. Day 5/Wednesday, a widespread, potentially substantial severe event remains apparent, and with greater agreement within the models with respect to the upper trough advance and associated positioning of the surface low/cold front, greater confidence with respect to the degree of risk exists. While a very similar 15% risk area will be depicted as in yesterday's outlook, a 30% area is being introduced from Arkansas northeastward to the mid Ohio Valley. It appears that the environment will become conducive for supercells, with very large hail, damaging winds, and strong tornadoes all possible during the afternoon and evening hours. From Day 6 onward, the cold front will continue its eastward advance across the Ohio Valley and into/across the Northeast/New England. However, much slower southward progression of the cold front is expected, with an eventual drift northward as a warm front that then lingers/oscillates across the Ohio Valley/Mid South/central and southern Plains through the end of the period. This will occur as a slow-moving trough moves into the West, and eventually evolves into a cut-off low. While weak disturbances eject eastward through southwesterly flow aloft across the central U.S. -- each of which may bring rounds of convection/severe potential in the day 6-8 time frame, narrowing down specific/greater areas of potential is difficult at this time. ...Goss.. 03/29/2025 = = = 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) .