Thunderstorms developed near a cold front in Minnesota then tracked eastward through Wisconsin during late evening hours on Monday (8/26) into the early morning hours of Tuesday (8/27). The strongest storms produced damaging winds across northeast Wisconsin.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GRB wrote it up.
Thunderstorms developed near a cold front in Minnesota then tracked eastward through Wisconsin during late evening hours on Monday (8/26) into the early morning hours of Tuesday (8/27). The strongest storms produced damaging winds across northeast Wisconsin.
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 Aug 26, 6:03 PM CST, 3 hours 34 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Green Bay WI 703 PM CDT Mon Aug 26 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Heat indices around 100 this evening will ease off the rest of the night. Impactful heat continues on Tuesday for some, when heat indices may reach 95 to 100 over parts of central Wisconsin and the Fox Valley. - There is a slight risk of severe thunderstorms through Tuesday. At this time, it appears the greatest risk will occur after midnight tonight through early Tuesday morning. Damaging winds will be the primary concern. Another round is possible Tuesday afternoon into Tuesday evening; however, confidence is lower for this second round. - Temperatures will be at or below normal starting Wednesday. - Rain and thunderstorm return late Thursday into Friday. Probabilities of getting at least 1 inch of rain range from 20-50%. && .DISCUSSION... Issued at 347 PM CDT Mon Aug 26 2024 Short Term...Tonight and Tuesday The latest RAP analysis and satellite/radar imagery show a strong mid-level ridge axis centered from the mid-Mississippi Valley, across Wisconsin, to Lake Superior early this afternoon. With daytime heating, a widespread cumulus field develop over central and north-central Wisconsin by late this morning. Temperatures have warmed into the middle to upper 80s. Combined with dewpoints in the middle 70s, heat indices are reaching into the middle to upper 90s. Looking upstream, a cold front is draped across western to north-central Minnesota. Satellite imagery shows shallow cumulus clouds developing across northern Wisconsin this afternoon as a substantial capping inversion exists between 750 mb and 800 mb. Upstream thunderstorms are developing across Minnesota, which is progged to track through the area later tonight. CAMs models are still all over the place, with some models developing storms across north-central Wisconsin later this evening, while others wait until the thunderstorms across Minnesota develop further and ride the ridge in place across the western Great Lakes region. Given the substantial capping inversion in place, the later scenario with the ridge riders seems mostly likely. That being said, the model discrepancies do not lend a high level of confidence to the forecast. Any storms that do develop will likely be organized into a line, taking advantage of 1500-3000 J/kg of MUCAPE, with straight line winds being the main severe weather threat. Any storms that track through late tonight could linger well into Tuesday morning, depending on the CAMs model. The forecast for Tuesday is even more murky as lingering cloud cover would likely mute high temperatures, whereas any clearing would pose a threat for afternoon thunderstorms as instability soars to 1500 to 2500 J/kg. If there is enough clearing and instability, all forms of severe weather will be on the table given steep low level lapse rates and surface based convection as the cold front sweeps through the area. That being said, lingering cloud cover would likely keep the severe weather threat to a minimum. If there is enough clearing, high temperatures will likely get into the low 90s with heat index values well into the 90s and approaching 100 degrees. Given the uncertainty regarding this cloud cover, will not extend the Heat Advisory into Tuesday at this time. Long Term...Tuesday Night Through Monday Lots of uncertainty at the start of the long term period beginning 00Z/Wed. Many CAMs show precip/thunderstorms south or east of the area by this time; however, recent runs of the NAMNest in particular show another round of convection Tuesday evening. Given the surface front will still be departing, and a 500mb wave has yet to clip far northern Wisconsin, will carry chance/likely PoPs Tuesday evening, and then gradually lower PoPs into Wednesday morning, hanging around longest in northern WI. Instability will theoretically wane Tuesday evening, but given the complex nature of everything to happen before this time, severe storms could still be possible, especially north. The cold front will be past the area by Wednesday, bringing cooler and slightly less humid air to northeast WI. High temps on Wednesday will range from the upper 60s to upper 70s, coolest in far north- central Wisconsin. Rain/thunderstorm chances return Thursday afternoon into Friday ahead of an approaching shortwave and frontal system. Timing is not certain, but the current depictions show the best timing is overnight, which would be less favorable for strong or severe thunderstorms. Pwats climb as high as 2.0 inches which will bring a heavy rain threat. Precip-free days appear most favorable from midday Friday into next Monday; although some weak shortwave energy could produce some spotty showers this weekend. Temperatures will be near normal Thu-Sat, and then fall a few degrees below normal Sun-Mon. This generally means highs in the upper 60 to low 80s, and lows in the 40s and 50s. && .AVIATION...for 00Z TAF Issuance Issued at 657 PM CDT Mon Aug 26 2024 Focus through Tuesday afternoon is on thunderstorm potential. Quiet at this time. Isolated storms stretch from northwest WI to western Upper Michigan, but these should remain north of RHI. Cluster of storms over central MN just west of MSP are poised to push into western WI 01z-03z. If these hold together they would reach western TAF sites (CWA, AUW and RHI) after 05z, then make it to east-central WI TAFs after 09z. Have shaped updated TAFs this way for now. Brief IFR conditions will occur during thunderstorms. Given how humid it is already, mainly MVFR cigs and/or vsby would likely linger a few hours even after the storms exit. No thunderstorm wind gusts highlighted at this time, but will monitor as the evening progresses and add them if needed. Once this round of storms moves out 11z-13z Tuesday, there remains questions on whether more storms will form during peak heating of the day as there may be a lot of debris clouds around in wake of the storms. Even so, there will be abundant instability present ahead of cold front and maybe enough time for recovery to develop additional storms mid to late afternoon. For now, placed a small mention of storms in the western TAFs closer to the cold front. && .GRB WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for WIZ018-020-030-031- 035>039-045-048-049-074. && DISCUSSION.....Kurimski/KLJ AVIATION.......JLA
Hazardous Weather Outlook...UPDATED National Weather Service Green Bay WI 912 PM CDT Mon Aug 26 2024 WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-280215- 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- 912 PM CDT Mon Aug 26 2024 This Hazardous Weather Outlook is for north-central and northeast Wisconsin. .DAY ONE...Tonight A line of severe storms is expected to shift into central Wisconsin by midnight and sweep across much of the area through the early morning hours. Damaging wind gusts to 60 mph will be the primary threat. Brief, but torrential downpours will accompany the storms as well. Severe thunderstorm watch 653 is in effect until 4 am Tuesday morning. .DAYS TWO THROUGH SEVEN...Tuesday through Monday Impactful heat and humidity will continue on Tuesday, though heat indices are expected to be slightly cooler. Additional strong to severe storms are possible Tuesday afternoon and evening, but development is uncertain due to potential impacts from the the storms that occur later tonight into early Tuesday morning. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed late this evening and overnight. LMZ521-522-541>543-280215- The Bay of Green Bay south of a line from Cedar River MI to Rock Island Passage-Lake Michigan from Washington Island to Sheboygan- 912 PM CDT Mon Aug 26 2024 This Hazardous Weather Outlook is for portions of northwest Lake Michigan and the waters of Green Bay. .DAY ONE...Tonight A line of strong to severe storms are expected after midnight. The primary hazard will be damaging winds. Brief heavy rain will also accompany the storms. Severe thunderstorm watch 653 is in effect until 4 am Tuesday morning. .DAYS TWO THROUGH SEVEN...Tuesday through Monday Strong to severe storms may be possible Tuesday afternoon and evening, but development is uncertain due to potential impacts from the the storms that occur later tonight into early Tuesday morning. Any storm will pose a threat to mariners. More thunderstorms are possible Thursday night and Friday morning which would pose a hazard to mariners. JLA
Preliminary Local Storm Report
National Weather Service Green Bay WI
1034 PM CDT Mon Aug 26 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1030 PM Tstm Wnd Gst 1 N Colby 44.92N 90.30W
08/26/2024 E50 MPH Marathon WI Trained Spotter
Spotter estimated winds of 40 to 50 mph and
also recorded pea size hail. Torrential
rainfall was also occurring with poor
visibilities.
&&The La Crosse radar (KARX), 123 km away, was scanning. The volume nearest the first event began at 03:39 UTC.
7 thunderstorm wind. Local standard time, as filed.
Thunderstorm winds downed trees in Marshfield. The time of this report is an estimate based on radar.
Thunderstorm winds downed trees in Spencer. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees in Winchester. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees in St. Germain. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees in Conover. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees in the town of Hutchins. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees and power lines in Green Bay. The time of this report is an estimate based on radar data.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2024Every state in 2024This day in weather historyWarnings in Wisconsin, August 2024
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: 1197781, 1197782, 1197783, 1197784, 1197785, 1197786, 1197790.