Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 27 2025 19:31:22 ACUS03 KWNS 271931 SWODY3 SPC AC 271930 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Fri Jun 27 2025 Valid 291200Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE UPPER MIDWEST... ....SUMMARY... Scattered strong to severe storms appear possible Sunday from the central Great Plains into the upper Great Lakes region, with at least some potential for the evolution of a large, organized severe storm cluster across parts of the mid into lower Missouri Valley and central Great Plains late Sunday through Sunday night. ....Discussion... Stronger westerlies will remain confined to the northern mid-latitudes, but models indicate further amplification of flow across the northeastern Pacific into interior North America through this period. This is forecast to include building mid/upper ridging across British Columbia through the western Canadian Prairies and northern U.S. Rockies, and digging downstream troughing across the international border toward the Upper Midwest. As mid-level flow transitions from westerly to northwesterly across the northern Rockies toward the middle/lower Missouri Valley, an initially prominent plume of warm elevated mixed-layer air advecting to the east of the Rockies is likely to become increasingly suppressed southward/southwestward into and through the central Great Plains by early Monday. Although the main surface cold front may only reach the Upper Midwest into high plains to the south of the Black Hills, this may be preceded by a notable wind shift, reinforced by considerable convective outflow through much of the central Great Plains into middle Mississippi Valley. ....Central Great Plains into middle/lower Missouri Valley... There is a notable signal within the model output that a large reservoir of moderate to strong potential instability, beneath the plume of warm elevated mixed-layer air, may provide support for one or two significant upscale growing clusters of thunderstorms Sunday through Sunday night. There remains sizable spread among the various output concerning where, ranging from near/east of the mid into lower Missouri Valley to portions of western Nebraska into Kansas. Much may depend on the evolution of a possible evolving cluster of storms, and its outflow, across southern South Dakota/northern Nebraska Saturday night, and the extent of the suppression of the elevated mixed-layer by early Sunday, which remain unclear. Stronger instability may tend to become displaced to the south of the stronger westerlies, but modest shear due to veering winds with height, coupled the thermodynamic profiles, characterized by unsaturated lower/mid-levels, with steep lapse rates and large CAPE, seem likely to become supportive of organized convection with strong cold pools capable of producing swaths of strong to severe surface gusts. Severe probabilities will probably need to be upgraded once lingering uncertainties become better resolved. ....Upper Midwest... If early period convection does not impact subsequent destabilization near/ahead of the southeastward advancing frontal zone, it still appears possible that deep-layer shear and forcing for ascent downstream of the digging short wave trough could support scattered strong to severe storm development in a corridor across southwestern through northeastern Wisconsin and portions of adjacent states. ...Kerr.. 06/27/2025 $$ = = = 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) .