Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 11 2025 19:28:58 ACUS03 KWNS 111928 SWODY3 SPC AC 111927 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ....SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ....Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ....Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ...Kerr.. 08/11/2025 $$ = = = 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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .