Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 21 2025 19:16:25 ACUS03 KWNS 211914 SWODY3 SPC AC 211914 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0214 PM CDT Sat Jun 21 2025 Valid 231200Z - 241200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE GREAT LAKES... ....SUMMARY... Strong to potentially severe storms may develop on Monday, from parts of the Great Lakes into the central Plains. ....Synopsis... Broad mid-level troughing across the western U.S., as well as upper ridging across the eastern CONUS, will remain in place Monday. The embedded mid-level shortwave trough and associated surface low over the northern U.S. on Day 2 (Sunday) will eject into Ontario on Monday. As such, overall synoptic ascent will decrease across the northern/central CONUS through the period. Nonetheless, surface lee troughing and a trailing frontal boundary will serve as the impetus for thunderstorm development across parts of the Great Lakes into the central Plains, where adequate buoyancy will support strong to potentially severe thunderstorms. ....Great Lakes/Upper Midwest... Thunderstorm development is likely along or immediately ahead of the frontal boundary by Monday afternoon. Deep-layer flow/shear will be oriented roughly parallel to the surface boundary, encouraging mainly multicellular/linear structures. 30 kts of effective bulk shear will be in place, amid 2000 J/kg MLCAPE, driven by 7 C/km mid-level lapse rates atop 70 F surface dewpoints. As such, the more robust, longer-lived storms may support a few instances of severe wind and/or hail. ....Portions of the central Plains... Thunderstorms may develop immediately along the surface boundary, as well as behind the front across the central Plains by afternoon peak heating. Deep-layer shear will be weaker here compared to the Great Lakes, though low-level lapse rates may be steeper (i.e. over 8.5 C/km), yielding MLCAPE values at least in the 2000-3000 J/kg range. As such, any of the more intense pulse cellular or multicellular storms that develop may produce few severe gusts. ....New England... Strong to locally extreme buoyancy, driven by a residual EML, will meander over the Mid Atlantic to New England on Monday as a surface anticyclone and associated upper ridge remains in place. Upper support is lacking for appreciable thunderstorm development. Some of the latest guidance suggests that strong thunderstorm potential will be confined to the periphery of the upper ridge over central Quebec. However, thunderstorm probabilities have been maintained given the possibility of a trailing stray storm over southern Quebec potentially impinging on northern New England. ...Squitieri.. 06/21/2025 $$ = = = 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) .