Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 18 2025 07:33:17 ACUS03 KWNS 180731 SWODY3 SPC AC 180730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Wed Jun 18 2025 Valid 201200Z - 211200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MIDWEST/GREAT LAKES... ....SUMMARY... Severe thunderstorms may develop Friday into Friday night across parts of the northern Plains and upper Midwest. ....Synopsis... An upper-level ridge is forecast to amplify on Friday from the southern Plains into parts of the MS/OH Valleys, as a seasonably deep mid/upper-level trough moves gradually eastward over the West. Rich low-level moisture will continue to stream northward to the east of a deepening lee surface cyclone across the northern High Plains. Multiple shortwaves may emanate out of the western trough and traverse the periphery of the building ridge from the northern Rockies/Plains into the Upper Midwest and parts of Great Lakes. ....Northern Great Plains into the Upper Midwest/Great Lakes... Uncertainty remains high regarding the details of convective evolution Friday into Friday night, but potential for severe storm development within a relatively volatile environment remains evident. To the east of the High Plains cyclone and trailing surface trough, and along/south of an effective warm front, strong to extreme buoyancy will develop Friday afternoon across parts of the central/northern Plains into the Upper Midwest. Details of diurnal storm development (if any) within this regime remain unclear. Warming temperatures aloft may tend to suppress development across the warm sector, but shortwaves emanating out of the western mid/upper-level trough may aid in development of an isolated supercell or two near the surface trough/dryline and/or effective warm front. Any surface-based development within this regime could pose a threat for all severe hazards. A somewhat more likely scenario is for storms to expand in coverage near/north of the warm front during the evening, in response to a strengthening low-level jet and related warm-advection regime. Large to extreme buoyancy and favorable deep-layer shear will support organized convection, with upscale growth into a potentially intense MCS possible with time. At this time, the most likely MCS corridor appears to be somewhere from eastern ND into central/northern MN, northern WI, and upper MI, though uncertainty remains high due to varying guidance solutions regarding the location of the warm front and evolution of the low-level jet. Despite the remaining uncertainty, a Slight Risk has been added given the conditional potential for significant severe weather. Some adjustments to this area will likely be needed with time, along with possible upgrades. ....Montana... Low-level easterly flow will transport modest moisture into parts of central/western MT during the day on Friday. Increasingly difluent upper-level flow associated with the deep western trough will support development of scattered to numerous thunderstorms through the day into Friday night. Elongated hodographs will support organized storms, with a threat of at least isolated hail and strong to severe gusts with initial convection over western MT. One or more clusters may move into central and northeast MT by evening, with a continued threat of severe gusts and hail. Depending on trends regarding destabilization, greater severe probabilities may eventually be needed. ....Lower Great Lakes into the Northeast... Modest low-level moistening is possible during the day on Friday from the lower Great Lakes into the Northeast, within a developing northwesterly flow regime in the wake of a departing mid/upper-level trough. While wind profiles may become somewhat favorable for organized convection, relatively cool post-frontal conditions and generally weak midlevel lapse rates will tend to limit destabilization, and any foci for robust storm development are not clear at this time. ...Dean.. 06/18/2025 $$ = = = 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) .