Subj : DAY2SVR: Marginal Risk To : All From : Mike Powell Date : Wed Aug 23 2023 07:48:00 ACUS02 KWNS 230457 SWODY2 SPC AC 230456 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1156 PM CDT Tue Aug 22 2023 Valid 241200Z - 251200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THURSDAY AFTERNOON INTO THURSDAY NIGHT ACROSS PARTS OF SOUTHEASTERN WISCONSIN...NORTHEASTERN ILLINOIS...SOUTHERN LOWER MICHIGAN...NORTHEASTERN INDIANA...MUCH OF OHIO AND WEST VIRGINIA...PARTS OF WESTERN MARYLAND AND WESTERN PENNSYLVANIA... ....SUMMARY... Strong thunderstorms may impact southern portions of the Great Lakes region into the upper Ohio Valley late Thursday afternoon into Thursday night, posing at least some risk for potentially damaging wind gusts. ....Synopsis... Further suppression of the persistent interior U.S. ridging appears likely to remain gradual, particularly at mid/upper levels, through this period. A significant short wave impulse initially digging within the primary belt of westerlies is forecast to turn east of Hudson Bay through northern Quebec, while a more modest perturbation emerging from the Pacific Northwest more slowly digs east-southeast of the Canadian Prairies into the central Canadian/U.S. border vicinity. Downstream of this latter feature, models indicate that flow will remain broadly anticyclonic across the Upper Midwest into the lee of the lower Great Lakes. In somewhat lower levels (850-700 mb layer), a wave on the leading edge of broad troughing is forecast to dig east-southeast of the Upper Midwest through lower Great Lakes and upper Ohio Valley vicinity by late Thursday night. Meanwhile, a prominent mid-level height center likely will be maintained across the southern Great Plains, with the remnants of Harold migrating within weak southerly flow around its western periphery, downstream of consolidating large-scale mid-level troughing near and offshore of the Pacific coast. ....Southern Great Lakes into upper Ohio Valley... It still appears that a notable cold front may surge south the Upper Midwest and Great Lakes region late Thursday through Thursday night, beneath lingering relatively warm air along the northeastern periphery of the upper ridging and, increasingly, south of the stronger westerlies. In advance of the front, areas of weakening warm advection driven convection may be ongoing early Thursday to the southeast and south of the lower Great Lakes region. However, beneath a remnant plume of warm elevated mixed-layer air, large pre-frontal boundary-layer CAPE may develop upstream through the day in response to strong surface heating of a very moist air characterized 70F+ dew points. And this should tend to advect eastward toward the Lake Erie and upper Ohio Valley vicinity into Thursday evening, as westerly flow in the 850-700 mb layer strengthens to 30-40 kt. Although upper support for sustained thunderstorm development remains unclear, it appears that there may be sufficient weakening of inhibition to allow for the initiation of at least widely scattered thunderstorm activity near/just ahead of the surface front by late Thursday afternoon. Some of this may pose a risk for marginally severe hail and strong downbursts into Thursday evening, before perhaps tending to grow upscale, mainly across parts of southeastern Lower Michigan and northeastern Indiana through northern and eastern Ohio. It is possible that at least a loosely organized cluster and cold pool could evolve and pose a risk for potentially damaging wind gusts into western Pennsylvania and northern West Virginia, before gradually weakening Thursday night. Due to lingering model variability and uncertainties, severe probabilities are being maintained at 5 percent, but higher severe wind probabilities could still be introduced in later outlooks for this time period. ...Kerr.. 08/23/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .