


Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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970 FXUS63 KGRB 262321 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 621 PM CDT Thu Jun 26 2025 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - There is a slight risk of severe thunderstorms in central Wisconsin and the southern Fox Valley late this afternoon and evening. Damaging winds and a few tornadoes are possible. The greatest threat is expected southwest of a line from Marshfield to Oshkosh. Severe weather will be most likely between 4 pm and 10 pm. - A Flood Watch has been issued for central Wisconsin and the southern Fox Valley, where soils are already saturated and additional rainfall amounts of 1.5 to 3 inches are expected. Areas with greatest flood potential include low-lying and urban areas, though localized river flooding may also occur. - Near/below temperatures continue through Friday, then increasing heat and humidity into the weekend, with highs near 90 by Sunday. - There is a chance of strong to severe storms late this weekend, especially Sunday afternoon and evening. && .DISCUSSION... Issued at 259 PM CDT Thu Jun 26 2025 Forecast concerns include severe weather and flooding potential through this evening, and another couple rounds of strong to severe storms from Saturday night through Sunday evening. Heavy Rainfall/Flooding Concerns: Will continue the Flood Watch for Wood, Portage, Waupaca, Waushara and Winnebago counties from 4 pm today through 4 am Friday. Much of this area has received 1.5 to 3 inches of rain since Monday, so soils are saturated. A west to east line of storms extending from KLSE-KDLL-KUNU will continue to lift north into our southern counties between 4-5 pm, followed by a well-developed squall line crossing central and east central WI from 6-10 pm. Both of these lines will be capable of producing torrential rainfall, given PWATs approaching 2 inches, and enough elevated instability to support higher rainfall rates with convection. The end time of the watch is likely longer than it needs to be, as most of the heavier rain will be gone by late evening, but wanted to match the end time of ARX`s Flood Watch to our southwest. Severe Weather Threat Through This Evening: Most models keep the warm front and associated surface based instability south of the forecast area late this afternoon/evening, but given the close proximity of the front (shallow stable layer near the surface), MUCAPE of 500-1000 j/kg, deep layer shear of 40-45 kts, 0-3 km SRH of 200-300 m2/s2, there is potential for supercells with damaging winds and a few tornadoes, especially in our far southwest counties. CAMs show development starting in our far southwest by 4-5 pm. A squall line will also move through C/EC from west to east between 6 and 10 pm, with potential for sporadic strong to damaging gusts. Rest of the Forecast: Quieter conditions expected friday and Saturday, 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 Sunday night, and this should bring a good chance of storms. With SBCAPE rising to 2-4k j/kg on Sunday, there is ample instability to support severe storms. However, deep layer shear is on the weak side; around 20-25 knots. Drier and more comfortable condiitons are expected for much of the following work week. && .AVIATION...for 00Z TAF Issuance Issued at 621 PM CDT Thu Jun 26 2025 Generally poor flying conditions will move into the region during the TAF period from heavy rain and thunderstorms this evening, rain overnight, and low ceilings and fog by Friday morning. Most locations have MVFR to IFR ceilings moving into the region as showers and thunderstorms move in. Thunderstorm extent northwards seems uncertain, so only made brief mention for RHI. May need to extend thunder in this region if storms can work their way northwards, but certainty isn`t high. Elsewhere a band of thunderstorms will work its way across the region through the early overnight. Kept a TEMPO group in place for the main period of scattered thunderstorms this evening. A low stratus deck plus recent rain will likely lead to IFR and possibly even LIFR from fog in the morning hours Friday before some improvement is possible by the late morning to early afternoon. Most locations will still be sitting at MVFR by the early afternoon hours on Friday. && .GRB WATCHES/WARNINGS/ADVISORIES... Flood Watch until 4 AM CDT Friday for WIZ035>037-045-048. && $$ DISCUSSION.....Kieckbusch AVIATION.......Uhlmann