Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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371 FXUS63 KGRB 250006 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 706 PM CDT Mon Jun 24 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - A severe thunderstorm complex is expected to produce widespread damaging winds as it moves through the region in the late evening and overnight hours. Greatest impacts expected over central WI and the Fox Valley. - Conditions hazardous to small craft are expected late tonight into Tuesday along Lake Michigan. - Some rivers and streams will remain above bankfull into the middle of the week. - Next period of significant rain expected Friday into Friday night. && .DISCUSSION... Issued at 258 PM CDT Mon Jun 24 2024 Short Term...Tonight and Tuesday The main focus of the short term forecast will be the approaching severe weather for the overnight period tonight. A shortwave trough will trigger the development of a complex of thunderstorms over eastern Minnesota this evening, bringing it eastwards into and across Wisconsin overnight. Ahead of this system, strong low level flow will prime an axis instability from Minnesota through central WI. Any organized complex that forms will then ride along this axis of instability, crossing central to eastern Wisconsin sometime between 11 PM and 4 AM. General model consensus develops the upstream storms into a fast moving bowing thunderstorm complex, which would highlight damaging winds as the most impactful severe threat. A couple brief spin ups aren`t out of the question, as the 0-3km shear values will be favorable on the northern end of the line, but in the context of widespread strong winds, impacts between the two will likely not be much different. Hail does not seem likely by the time storms arrive. Finally, although another half inch to an inch of rain is possible, the fast moving nature of the anticipated storms will limit any flooding concerns but may keep river levels elevated. Storms will push through the region by around daybreak, with quieter conditions expected to return by Tuesday morning. The passage of the storms is expected to push the frontal boundary southwards, keeping any redevelopment Tuesday afternoon south of our area and focused more towards Illinois. Long Term...Tuesday Night Through Monday Little impactful weather is expected through Thursday night, with high pressure dominating for much of the period. A frontal system is forecast to move through the region Friday and Friday night. This system should have have a nice surge of Gulf of Mexico moisture, as a 40-50 kt LLJ brings PWATs around 2 inches into the region. Locally heavy rainfall will be a concern, but a lack of significant instability should limit the severe weather threat. Another system may bring showers and storms to the region early in the next work week. Temperatures should average near to slightly below normal through the extended period. && .AVIATION...for 00Z TAF Issuance Issued at 706 PM CDT Mon Jun 24 2024 VFR conditions will continue early this evening, then attention turns to the complex of storms expected late this evening into early Tuesday. CAMs and WoFS still showing a few different scenarios this evening/tonight as continue to struggle with the 3 areas of convection currently to our west and when the "main show" will start somewhere closer to Minneapolis as the LLJ refocuses. Still thinking the complex will arrive towards midnight in central and north-central WI, then race east through northeast WI. Storms can produce damaging winds, especially in central WI and may produce some hail and torrential downpours. Will continue to monitor and will try to refine timing as a clearer picture becomes evident. But for now, continued to highlight a 2-hour window for the storms. Some LLWS will be possible, when surface winds drop below 15 kts, ahead of the complex of storms as a LLJ works into the area. Will need to monitor for a wake low behind the complex of storms, which could produce strong easterly winds. Some low clouds could linger through around 15z on Tuesday, longest over east-central WI. Otherwise, look for VFR conditions on Tuesday. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement from 4 AM CDT Tuesday through Tuesday afternoon for WIZ022-040-050. && $$ DISCUSSION.....Uhlmann/Kieckbusch AVIATION.......Bersch