


Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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841 FXUS63 KGRB 250408 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1108 PM CDT Tue Jun 24 2025 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Periods of showers and thunderstorms expected Wednesday through Thursday night, with heavy rainfall expected. The probability of 2+ inches of rain is highest (30-60%) over central and north central WI. There is a slight risk of excessive rainfall and flooding through this period. - There is some potential for severe thunderstorms over mainly central and east central WI Thursday afternoon and evening. - Much cooler temperatures through Thursday, then a warm-up into the weekend. && .DISCUSSION... Issued at 339 PM CDT Tue Jun 24 2025 The forecast focus remains on heavy rainfall and flooding potential during the Wednesday through Thursday night period, and a possible severe weather threat over central and east central WI Thursday afternoon and evening. A cold front pushed through the forecast area this afternoon, accompanied by drier air. Dew points had dropped into the middle 40s to lower 50s in far north central WI, but were still well into the 60s in the southeast part of the forecast area. Showers in association with the front have decreased considerably over the past couple hours, and should continue to diminish through sunset. Expect a generally dry night tonight as Canadian high pressure sets up just to our north. A much more comfortable night is anticipated, with lows in the 50s and lower 60s. Heavy rainfall/Flooding and Thunderstorm Chances Wednesday through Thursday Night: Showers and a few embedded storms will gradually increase from SW to NE on Wednesday, as an 850 mb warm front lifts north into the region, mid-level frontogenesis increases, a short-wave trough moves through, and deeper moisture returns. Most of this rainfall is expected to be light to moderate, though some heavier pockets of rain could arrive in C/NC WI later in the day. The 850 mb front will continue to shift north through the forecast area on Wednesday night, and pockets of strong frontogenetic forcing will bring increased potential for heavy rainfall. The best conditions for heavy rainfall may actually occur Thursday into Thursday night, as an impressively moist air mass (PWATs of 2-2.25 inches/200+ percent of normal/ near or above climatological max for GRB) move into C/EC WI, a surface lows moves through and lifts the surface warm front into the southern part of the forecast area, frontogenetic forcing continues and a short-wave moves through. Instability also increases on Thursday, setting the stage for increased convective input/higher rainfall rates. What is still uncertain through this period is exactly where the heaviest rainfall will set up. At this point, the highest probabilities (30-60%) for 2+ inches of rain remain across C/NC WI. There is increasing concern for a severe thunderstorm threat on Thursday afternoon/evening, as the warm front lifts into our southern counties. If the front makes it, SBCAPE is expected to reach 1-2K j/kg, with sufficient shear (0-6km bulk shear of 25-40 kts, and 0-3km SRH of 150-300) to support severe storms. Will take a closer look at this tomorrow. Rest of the Forecast: Quieter conditions expected, with warmer temperatures in the 80s arriving for the weekend. A weak cold front is expected to approach the region Saturday night, then move through on Sunday, and this could bring a chance of storms. && .AVIATION...for 06Z TAF Issuance Issued at 1107 PM CDT Tue Jun 24 2025 Some isolated pockets of MVFR conditions late this evening with dips to BKN low clouds a times, otherwise VFR conditions should persist overnight into Wednesday morning. Clouds thicken up late Wednesday morning, with rain with embedded thunderstorms to spread across the area from SW to NE late Wednesday morning and afternoon. MVFR with localized IFR to occur as the precip arrives. Winds will generally be light from the E/NE. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch AVIATION.......KLJ