Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 15 2025 05:59:10 ACUS02 KWNS 150558 SWODY2 SPC AC 150556 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Fri Aug 15 2025 Valid 161200Z - 171200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN HIGH PLAINS EASTWARD TO THE GREAT LAKES... ....SUMMARY... Thunderstorms with a potential for isolated severe gusts and hail will be possible on Saturday from parts of the central and northern Plains eastward to the Great Lakes. ....Central and Northern Plains... At mid-levels, a ridge will move across the northern Plains on Saturday, as southwesterly flow remains from the northern Rockies into the northern High Plains. At the surface, an upslope flow regime will remain in place from the Dakotas into eastern Montana. A surface trough will deepen during the day over the northern High Plains. Although large-scale ascent will remain weak across the region, isolated thunderstorms may develop in the afternoon near the surface trough. Additional isolated storms could develop near and to the north of a front located across northern Nebraska. To the north of the front, a moist and unstable airmass is forecast. Moderate instability will be in place over much of this airmass by afternoon. Although deep-layer shear will remain near or below 35 knots over most of this airmass, low to mid-level lapse rates will be steep. This could be enough for isolated severe gusts and hail with any cell that can develop and persist in the late afternoon and early evening. ....Upper Mississippi Valley/Great Lakes... West-northwesterly mid-level flow will remain in place on Saturday from the upper Mississippi Valley into the Great Lakes, as a mid-level ridge moves across the northern Plains. At the surface, a front is forecast to remain in place from far northern Iowa into southern Wisconsin. From near the boundary southward, surface dewpoints are forecast to be in the lower to mid 70s F. This will contribute to a strongly unstable airmass by afternoon. Although large-scale ascent will remain weak across the region, isolated thunderstorms may develop along pre-existing boundaries or along zones of maximized low-level convergence. NAM forecast soundings near and to the north of the front across the upper Mississippi Valley have 0-6 km shear in the 30 to 40 knot range, with 700-500 mb lapse rates of 7 to 7.5 C/km. This could be enough for isolated rotating storms with potential for hail and severe wind gusts. A potential for severe gusts could extend eastward into parts of the Great Lakes where moderate instability is forecast, but deep-layer shear will be more modest. ...Broyles.. 08/15/2025 $$ = = = 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) .