Scattered thunderstorms tracked through the region during the early morning hours on Saturday (9/20). One storm produced an isolated wind gust to 60 mph in Oshkosh.
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The episode as NWS GRB wrote it up.
Scattered thunderstorms tracked through the region during the early morning hours on Saturday (9/20). One storm produced an isolated wind gust to 60 mph in Oshkosh.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Green Bay, WI wrote its last area forecast discussion before the first event at Sep 19, 9:47 PM CST, 2 hours 14 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Green Bay WI 1047 PM CDT Fri Sep 19 2025 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Multiple rounds of showers and thunderstorms are expected this afternoon through the weekend. Isolated strong storms with gusty winds and small hail will be possible during this time. - Heavy rain and localized flooding will be possible with any shower or storm activity this weekend. The greatest chances for heavier rain will be over central Wisconsin on Saturday. - Breezy southeast winds will result in hazardous marine and beach conditions south of Sturgeon Bay late tonight through early Saturday afternoon. && .DISCUSSION... Issued at 249 PM CDT Fri Sep 19 2025 Short Term...Tonight and Saturday This afternoon... GOES water vapor imagery shows driving upper- level trough currently residing over the northern Plains. Low- level moisture transport continues to flow out ahead of a quasi- stationary boundary to the southwest as instability builds across our southern tiers of counties. As a result, additional storm activity is expected to start popping up in central Wisconsin within the next hour or two. Showers over portions of central to north-central Wisconsin have a history of producing heavy rain as of early this afternoon. Forecast through Saturday remains low predictability as CAMs struggle to get a hold on the convoluted synoptic pattern. Looking at the big picture, the 500 mb wave train ramps up heading into the weekend, and is forecast to interact with plentiful moisture aloft. Result will be several rounds of rain/storms across northeast Wisconsin through Saturday evening. However, given the complex nature of the current pattern paired with poor CAM performance, would feel low confidence in adding any finer details to the forecast. Rain/storm chances... Scattered showers and storms remain possible through the remainder of the afternoon into this evening as instability continues to nose into central Wisconsin. Main concern will be pockets of heavy rainfall as low pressure over northeast South Dakota ushers in a conveyor belt of PWATs approaching 200% of normal. Heavy rain/flooding threat would be further evidenced by light winds below around 700 mb, which would be conducive to training/slow-moving cells. Showers and storms then spread north and east overnight into Saturday morning as more robust shortwave energy pivots over the upper Mississippi Valley. Some CAMs suggest that there could be a brief lull in activity later Saturday morning before more diurnally-driven storms pop along the instability gradient (~1,000 to 1,200 J/kg MUCAPE) early Saturday afternoon. Heavy rain and localized flooding would once again be the main concern with these storms, though any stronger cells could produce gusty winds and small hail. This being said, deep layer shear below 20 knots should prevent any organization of stronger storms. Greatest risk for heavy rainfall remains over central Wisconsin. Marine hazards... Increasing southeast winds and waves building 3 to 5 ft will result in conditions hazardous to small craft along Lake Michigan nearshore waters on Saturday. As such, there will also be increased potential for rip currents along Lake Michigan beaches in Kewaunee and Manitowoc counties. Marine and Beach Hazards headlines have been issued, and small craft are encouraged to exercise caution on the Bay late this afternoon into early Saturday morning. Long Term...Saturday Night Through Friday Unsettled weather continues Saturday night into early next week as a slow moving upper trough moves across the Upper Midwest and Great Lakes. This will keep periodic rain chances (30-70%) in the forecast as shortwaves rotate through the upper trough. Rain chances will decrease Saturday night as one of the shortwaves exits, with another one forecast to arrive Sunday afternoon/evening, with the showers once again becoming more widespread. A couple more shortwaves, along with a weak frontal boundary, are forecast to move across the area Sunday night into Monday, continuing the chances for rain. Thunder chances will be limited due to cloud cover and marginal instability and deep layer shear. But with up to ~1000 J/kg of MUCAPE, isolated storms are expected at times. A couple could be on the stronger side, but the risk for severe weather is low. The showers and storms will also bring an isolated flooding threat into early next week. PWATs will be running between 1.0-1.30" (125-175% of normal), so any training cells could pose a flood risk, especially for any areas that receive the heavier rainfall today and Saturday. But with the longer range ensemble guidance still showing under 20% chances of 1"+ in any one 24-hour period, along with breaks in the heavier bouts of precip, the overall flood threat will be low. The lingering trough could keep some lighter showers in the area on Tuesday, especially south, then a drier and less unsettled stretch of weather is expected during the middle of next week as an upper low becomes cut-off just south of the Great Lakes. Some disagreement how long it will be far enough to our south to keep the area dry, but should get at least a day or two of dry conditions. Then, as the low drifts north/east, chances for showers and a few storms returns to the region late in the week and into next weekend. Temps through the period look to be near or a little above average. && .AVIATION...for 06Z TAF Issuance Issued at 1047 PM CDT Fri Sep 19 2025 Main aviation concern will be the continued presence of showers and potential thunder in the region. The next round of showers is on its way into the region from the south and will likely affect central to east-central Wisconsin by 06Z. Included a mention of showers across all sites but RHI, and also included a mention of thunder possible at times overnight. Ceilings with this wave vary, from IFR over central Wisconsin behind the rain from earlier in the evening to still VFR over the Fox Valley and Lake Michigan shoreline. As we get into Saturday morning, another push of more broad precipitation is expected, with showers and embedded storms likely to pass over much of the region. Retained mention of showers and a few areas of thunder for this period. There are still likely to be a couple of breaks in the action on Saturday, with the most likely period being some time in the early to mid afternoon before another round of rain moves through. Predictability for this break remains low, so did not try to refine to specific hours in the TAF. Ceilings during this period will likely be on their way downwards towards MVFR over the Fox Valley and IFR further west. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement through Saturday afternoon for WIZ040- 050. && DISCUSSION.....Goodin/Bersch AVIATION.......Uhlmann
Hazardous Weather Outlook National Weather Service Green Bay WI 308 PM CDT Fri Sep 19 2025 WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-202015- Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln- Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano- Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago- Calumet-Manitowoc-Southern Marinette County- Southern Oconto County- 308 PM CDT Fri Sep 19 2025 This Hazardous Weather Outlook is for north-central and northeast Wisconsin. .DAY ONE...Tonight Isolated to scattered thunderstorms are expected over most of the area. Although the strongest storms could produce small hail and gusty winds, the risk of severe weather is low. Heavy rainfall and localized flooding is possible. There is an increased risk for rip currents on Lake Michigan beaches in Kewaunee and Manitowoc counties beginning after midnight tonight. .DAYS TWO THROUGH SEVEN...Saturday through Friday Thunderstorms will be possible at times this weekend through early next week. The risk of severe weather remains low. Heavy rainfall and localized flooding is possible. Potential for rip currents on Lake Michigan beaches continues through early Saturday afternoon. .SPOTTER INFORMATION STATEMENT... Spotters are requested to report any hail and flooding to the National Weather Service in Green Bay. LMZ521-522-541>543-202015- The Bay of Green Bay south of a line from Cedar River MI to Rock Island Passage-Lake Michigan from Washington Island to Sheboygan- 308 PM CDT Fri Sep 19 2025 This Hazardous Weather Outlook is for portions of northwest Lake Michigan and the waters of Green Bay. .DAY ONE...Tonight Isolated to scattered thunderstorms are possible. Any storm could pose a hazard to mariners. Gusty southeast winds will result in conditions hazardous to small craft beginning after midnight for the Lake Michigan nearshore waters. Additionally, small craft are encouraged to exercise caution on the Bay this evening into early Saturday morning. .DAYS TWO THROUGH SEVEN...Saturday through Friday Thunderstorms will be possible at times this weekend through early next week. Any storm could pose a hazard to mariners. Conditions hazardous to small craft continue through early Saturday afternoon. Goodin/Bersch
The Green Bay radar (KGRB), 65 km away, was scanning. The volume nearest the first event began at 06:00 UTC.
1 thunderstorm wind. Local standard time, as filed.
Thunderstorms produced a wind gust to 60 mph at the Oshkosh airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2025Every state in 2025This day in weather historyWarnings in Wisconsin, September 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1291704.