Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 20 2025 06:06:22 ACUS02 KWNS 200606 SWODY2 SPC AC 200604 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Fri Jun 20 2025 Valid 211200Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN GREAT LAKES INTO NY AND NORTHERN PA... ....SUMMARY... Strong to locally severe storms are possible Saturday from the northern Great Plains into the Upper Midwest and Great Lakes. ....Synopsis... A deep mid/upper-level trough will move gradually eastward across the western CONUS on Saturday, as an embedded shortwave trough moves from parts ID/MT into the Canadian Prairies. A surface low initially over the northern Plains is forecast to move northeast through the day, with a secondary surface low expected to develop along a cold front across the central High Plains during the evening. Downstream, a mid/upper-level shortwave trough (possibly augmented by D1/Friday MCS development) is generally forecast to move from the northern Great Lakes toward New England. ....Great Lakes into the Northeast... An MCS will likely be ongoing Saturday morning across parts of the northern Great Lakes, with other areas of elevated convection possible farther south across lower MI. While there is some uncertainty regarding MCS timing, some damaging-wind and hail threat would accompany this system and any other robust morning convection before spreading into Ontario. The convectively augmented shortwave trough associated with the potential MCS may continue to impinge upon the northeast periphery of an expanding instability reservoir. Even if the morning MCS weakens or stays in Canada, strong to potentially severe storms may spread southward out of Ontario into the lower Great Lakes region, and/or develop within a low-level warm advection regime. Damaging winds may be the most common hazard, though low-level shear/SRH may become sufficient for a localized tornado threat as well. Convection may continue into late Saturday night with at least an isolated severe threat. Farther west, there is some potential for isolated storm development during the afternoon/evening across the northern Great Lakes vicinity, within a conditionally favorable environment. However, with large-scale ascent expected to remain rather nebulous in the wake of the departing MCS and shortwave trough, confidence is currently low regarding this scenario. ....Northern Plains into the Upper Midwest... While there is some lingering uncertainty regarding the influence of D1/Friday convection, strong to extreme buoyancy is likely to again develop across parts of the northern Plains and Upper Midwest, along and east of the cold front. However, very warm temperatures aloft and generally weak large-scale ascent may tend to suppress storm development across much of the strongly unstable warm sector. Strong heating could support isolated development across parts of NE/SD/eastern ND into northern MN near the surface low and front, which would conditionally pose a severe threat given the favorable parameter space. Farther northwest, guidance continues to vary regarding the magnitude of instability from eastern MT/northern WY into the western Dakotas. Strong morning convection will be possible across eastern MT, and some redevelopment may occur during the afternoon/evening, depending on the extent to which the departing MT shortwave trough can impinge upon favorable instability. A supercell or two will be possible, with a localized threat for all severe hazards. ...Dean.. 06/20/2025 $$ = = = 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) .