Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 11 2025 09:03:42 ACUS48 KWNS 110902 SWOD48 SPC AC 110900 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 11 2025 Valid 141200Z - 191200Z ....DISCUSSION... Latest medium-range output remains generally similar to prior runs concerning the pattern evolution Wednesday into Thursday. A significant short wave trough emerging from the Intermountain West is forecast to support modest cyclogenesis across the central and northern Great Plains through the mid/upper Mississippi Valley vicinity. It appears that this probably will be accompanied by increasing potential for strong to severe thunderstorm development, with severe probabilities maximizing across parts of the Midwest late Thursday into Thursday night, as the stronger large-scale forcing for ascent becomes better coupled with substantive boundary-layer moistening and destabilization. Aided by steep lower/mid-tropospheric lapse rates associated with elevated mixed-layer air, and moderate to strong low-level and deep-layer shear, it appears that the environment will become conducive to the evolution of an upscale growing and organizing convective system. But initial convection may include supercells posing a risk for large hail and a couple of tornadoes, before damaging wind gusts become the predominate severe hazard. Based on the subsequent pattern evolution, it appears that this convection could persist into, or re-intensify, Friday across parts of the mid/upper Ohio Valley, with additional upscale growing convection evolving along a stalling trailing cold front near the southern edge of the stronger westerlies. Into next weekend, renewed cyclogenesis appears possible along the trailing flank of the front across the south central Great Plains, where additional strong to severe thunderstorm development may focus along a developing warm front, and a developing dryline southward through the plains, as the warm sector destabilizes with increasing Gulf moisture return. However, by late Thursday into Friday, and beyond, these developments remain much more unclear, as spread among and within the various medium-range models begins to increase. Substantive differences begin to develop concerning the progressiveness of the lead trough, and a trailing short wave trough emerging from the mid-latitude Pacific. The uncertain impacts of potentially multiple evolving large convective clusters on succeeding days adds to low predictability. ...Kerr.. 05/11/2025 = = = 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) .