A few supercell thunderstorms developed over western Wisconsin and move east into southern Wisconsin. These eventually morphed into more of a thunderstorm complex as they entered southern Wisconsin.
Every event with a place to put it. Tap one for its entry below.
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 MKX wrote it up.
A few supercell thunderstorms developed over western Wisconsin and move east into southern Wisconsin. These eventually morphed into more of a thunderstorm complex as they entered southern Wisconsin. Strong to severe storms caused pockets of wind damage and a tornado.
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 Milwaukee, WI wrote its last area forecast discussion before the first event at Aug 7, 8:07 AM CST, 3 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 907 AM CDT Sat Aug 7 2021 .UPDATE... (Issued 907 AM CDT Sat Aug 7 2021) Ongoing convection to pass largely to our north. A shortwave/MCV connected to this activity is proggd to potentially impact the area later this afternoon into this evening. The concern with this is the proximity of the surface warm front and with likely an ample amount of instability we could see some discrete storms take shape. there is a window where there would be sufficient veering in the low levels as 850 winds turn southwest into SC WI while surface winds remain more southeast. Again, this is largely dependent on warm frontal positioning. Mesoscale models in various forms suggesting this possible scenario. After that MCV moves through early this evening we could see a break before renewed storms fire in conjunction with the LLJ axis. This would likely roll in overnight from the northwest following the Corfidi vectors. Still lots of uncertainty on how this will all play out. && .SHORT TERM... (Issued 320 AM CDT Sat Aug 7 2021) Today through Sunday: The active weather start to the weekend is expected to continue. Multiple upper level waves are expected to move through the flow today and tomorrow. With upper level PVA and the associated surface front in place over the Great Lakes Region throughout much of the weekend, there will be no shortage of lift and instability. The frontal boundary that moved southward across southern Wisconsin on Friday is expected to stall and then quickly turn back toward the north. As the frontal boundary moves back over southern Wisconsin during the morning hours we can expect the first of many rounds of storms. Warm air and moisture advection will continue throughout the day. Southern Wisconsin will once again be under the warm sector, so any isentropic lift or lift from the approaching upper level wave will be enough to generate scattered showers/storms during the afternoon hours. There is however, still a lot of uncertainty on if any storms will develop during the afternoon. Southern Wisconsin will have no shortage of instability or moisture during this time so any storm could bring heavy rainfall and could be strong/severe. By this evening, when the upper level wave is expected to move through there will be another round of showers/storms expected. Unfortunately this will be largely based on what has happened throughout the day. If rain showers/storms develop during the afternoon hours then the environment could be pretty worked over making any of the rain showers during the evening weaker. Given the uncertainty with the afternoon round of showers, if nothing develops and there is some afternoon clearing then the potential for severe weather overnight Saturday into Sunday will increase dramatically. The strength and location of the LLJ during the overnight hours will also play a large roll in where any strong storms will set up. Regardless of how things shake out today, there will be a chance for some strong/severe storms. The main hazards will be wind, hail, and heavy rainfall today. A tornado or two can not be ruled out however. With the deep moisture any storms that train over the same area throughout the day could bring some localized flooding. The chance for showers and storms will continue through much of the day on Sunday as one upper level wave begins to exit Wisconsin and another close on its heels. There could be a short reprieve during the late morning into the early afternoon hours before the next wave moves in, but this will be largely dependent on what happens overnight tonight. Regardless the chance for showers/storms will continue into the evening hours on Sunday. Patterson && .LONG TERM... (Issued 320 AM CDT Sat Aug 7 2021) Sunday night through Friday: Thunderstorms will be ongoing across the area Sunday evening into Sunday night as a shortwave passes through the area. There is considerable uncertainty regarding the details with this convection given that convective evolution today, tonight, and tomorrow will have major impacts on what things look like heading into Sunday evening and night. Nonetheless, do think that is more likely than not that the environment will be sufficient for at least a few strong to severe storms during this time. Wind and hail will be the main threats, along with locally heavy rain. Convection will likely percolate through the night Sunday night into Monday, with additional convection during the day Monday before the mid level trough axis finally pushes east of the area. Shortwave ridging looks to build into the area for Tuesday, before another trough approaches from the west Tuesday evening into Tuesday night. This will bring additional shower and storm chances to the region Tuesday night and Wednesday, and given the very unstable airmass across the region, some strong storms will again be possible. At least limited daily chances for showers and thunderstorms continue for Thursday. Extended guidance still suggests the arrival of a cooler and drier airmass by Friday or next weekend, which would bring an end to the rain chances to the area. Boxell && .AVIATION... (Issued 907 CDT Sat Aug 7 2021) Storms riding along and north of the warm front should stay north I-94 this morning. Upstream shortwave may lead to further discrete development later today into this evening especially across SC WI. Then LLJ will drive additional storms chances overnight. Activity would likely initiate to our northwest closer to LLJ axis and then propagate southeastward into southern WI. Still quite a bit if uncertainty with the details. IFR and MVFR cigs tied to that warm front may linger longer along and to the north of the boundary. && .MARINE... (Issued 320 AM CDT Sat Aug 7 2021) Winds have gradually weakened early this morning as the trough of low pressure continues to move east out of the Great Lakes Region. Another low is expected to move into the region tonight, which will cause the pressure gradient to tighten and the winds to pick up across the lake. Daily chances for thunderstorms continue today through early next week as multiple upper level disturbance track across the western Great Lakes Region. Patterson && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee
Hazardous Weather Outlook National Weather Service Milwaukee/Sullivan WI 324 AM CDT Sat Aug 7 2021 WIZ046-047-051-052-056>060-062>072-080830- Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge- Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee- Lafayette-Green-Rock-Walworth-Racine-Kenosha- 324 AM CDT Sat Aug 7 2021 This Hazardous Weather Outlook is for portions of east central Wisconsin, south central Wisconsin and southeast Wisconsin. .DAY ONE...Today and Tonight Chances for thunderstorms continue today with an increased chance of some stronger storms tonight into Sunday morning. Torrential rainfall will be possible, any training storms could cause localized flooding. .DAYS TWO THROUGH SEVEN...Sunday through Friday Chances for thunderstorms continue Sunday through early next week with stronger storms possible through Sunday night. As the heat and humidity build through the weekend, heat indices of 95-100 degrees are possible early next week. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. LMZ643>646-080830- Sheboygan to Port Washington WI- Port Washington to North Point Light WI- North Point Light to Wind Point WI- Wind Point WI to Winthrop Harbor IL- 324 AM CDT Sat Aug 7 2021 This Hazardous Weather Outlook is for the nearshore waters from Sheboygan Wisconsin to Winthrop Harbor Illinois. .DAY ONE...Today and Tonight Chances for thunderstorms continue today with an increased chance of some stronger storms tonight into Sunday morning. .DAYS TWO THROUGH SEVEN...Sunday through Friday There will be chances of thunderstorms Sunday through early next week. LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-080830- Lake Michigan Michigan City IN to St. Joseph MI 5 NM offshore to mid-line of lake.- Lake Michigan from Seul Choix Point to Rock Island Passage 5NM offshore to Mid Lake- Lake Michigan South of a line from Seul Choix Point to the Mackinac Bridge and North of a line from Charlevoix MI to South Fox Island 5NM offshore- Lake Michigan from Charlevoix to Point Betsie MI 5NM Offshore to mid lake- Lake Michigan from Point Betsie to Manistee MI 5NM offshore to Mid Lake- Lake Michigan from Rock Island Passage to Sturgeon Bay WI 5NM offshore to mid lake- Lake Michigan from Sturgeon Bay to Two Rivers WI 5NM offshore to Mid Lake- Lake Michigan from Two Rivers to Sheboygan WI 5NM offshore to Mid Lake- Lake Michigan from Sheboygan to Port Washington WI 5NM offshore to Mid Lake- Lake Michigan from Port Washington to North Point Light WI 5NM offshore to Mid Lake- Lake Michigan from North Point Light to Wind Point WI 5NM offshore to Mid Lake- Lake Michigan from Wind Point WI to Winthrop Harbor IL 5NM offshore to Mid Lake- Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5NM offshore to Mid Lake- Lake Michigan from Wilmette Harbor to Michigan City in 5NM offshore to Mid Lake- Lake Michigan from Pentwater to Manistee MI 5NM offshore to Mid Lake- Lake Michigan from Whitehall to Pentwater MI 5NM offshore to Mid Lake- Lake Michigan from Grand Haven to Whitehall MI 5NM offshore to Mid Lake- Lake Michigan from Holland to Grand Haven MI 5NM offshore to Mid Lake- Lake Michigan from South Haven to Holland MI 5NM offshore to Mid lake- Lake Michigan from St Joseph to South Haven MI 5NM offshore to Mid Lake- 324 AM CDT Sat Aug 7 2021 This Hazardous Weather Outlook is for the open waters of Lake Michigan. .DAY ONE...Today and Tonight Chances for thunderstorms continue today with an increased chance of some stronger storms tonight into Sunday morning. .DAYS TWO THROUGH SEVEN...Sunday through Friday Chances of thunderstorms continue Sunday through early next week. www.weather.gov/mkx
Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
1006 AM CDT Sat Aug 7 2021
WIZ046-056-057-071600-
Columbia WI-Marquette WI-Sauk WI-
1006 AM CDT Sat Aug 7 2021
...A strong thunderstorm will impact portions of northern Columbia,
Marquette and northern Sauk Counties through 1100 AM CDT...
At 1005 AM CDT, Doppler radar was tracking a strong thunderstorm 9
miles north of Wisconsin Dells, moving east at 40 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Baraboo, Portage, Reedsburg, Wisconsin Dells, Lake Wisconsin, Lake
Delton, Pardeeville, Montello, West Baraboo, Westfield, Rio,
Lawrence, Packwaukee, Wyocena, Mecan, Oxford, Endeavor, Neshkoro, La
Valle and Rock Springs.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4388 8917 4387 8920 4382 8920 4380 8919
4381 8917 4377 8917 4376 8925 4364 8925
4364 8917 4341 8919 4350 9019 4364 9020
4364 8960 4398 8960 4398 8917
TIME...MOT...LOC 1505Z 275DEG 33KT 4375 8983
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
MILLERSpecial Weather Statement
National Weather Service Milwaukee/Sullivan WI
1101 AM CDT Sat Aug 7 2021
WIZ046-047-051-057-058-071700-
Dodge WI-Columbia WI-Green Lake WI-Marquette WI-Fond Du Lac WI-
1101 AM CDT Sat Aug 7 2021
...Strong thunderstorms will impact portions of southern Green Lake,
west central Fond du Lac, eastern Columbia, southeastern Marquette
and western Dodge Counties through NOON CDT...
At 1101 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Montello to near Pardeeville to near Rio.
Movement was east at 30 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Beaver Dam, Columbus, Poynette, Pardeeville, Randolph, Fall River,
Montello, Markesan, Rio, Brandon, Cambria, Fox Lake, Alto,
Manchester, Wyocena, Reeseville, Mecan, Otsego, Fairwater and
Friesland.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Persons in campgrounds should consider seeking sturdy shelter until
these storms pass.
&&
LAT...LON 4378 8878 4325 8879 4337 8943 4363 8939
4382 8944
TIME...MOT...LOC 1601Z 280DEG 25KT 4374 8934 4362 8931 4346 8933
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
HANSENSpecial Weather Statement
National Weather Service Milwaukee/Sullivan WI
1147 AM CDT Sat Aug 7 2021
WIZ057-058-063-064-071745-
Dodge WI-Columbia WI-Jefferson WI-Dane WI-
1147 AM CDT Sat Aug 7 2021
...Strong thunderstorms will impact portions of southeastern
Columbia, northeastern Dane, northwestern Jefferson and southern
Dodge Counties through 1245 PM CDT...
At 1147 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles northeast of Fall River to near
Columbus to 6 miles north of Waterloo. Movement was southeast at 25
mph.
HAZARD...Wind gusts of 50 to 55 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Watertown, Beaver Dam, Jefferson, Lake Mills, Columbus, Marshall,
Waterloo, Juneau, Johnson Creek, Fall River, Hustisford, Lebanon,
Milford, Reeseville, Richwood, Clyman, Lowell, Hubbleton, Danville
and Pipersville.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Persons in campgrounds should consider seeking sturdy shelter until
these storms pass.
&&
LAT...LON 4336 8852 4296 8875 4325 8916 4339 8906
4357 8906
TIME...MOT...LOC 1647Z 303DEG 21KT 4346 8897 4335 8897 4327 8903
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH
HANSENThe Milwaukee radar (KMKX), 29 km away, was scanning. The volume nearest the first event began at 17:28 UTC.
5 thunderstorm wind, 1 hail, 1 tornado. Local standard time, as filed.
Large tree down along West St. in Watertown. Winds estimated at 60 mph. Pea size hail also occurred.
Measured at Watertown Airport. Also report of tree down along Boomer Street 1 mile south of Watertown.
Multiple reports of tennis ball sized hail from farmers in NW Iowa County.
This tornado spawned off of the same storm that produced the EF-3 tornado near Boscobel, but was clearly of a different track. This EF-1 went through mainly rural areas north to northeast of Highland. The main damage occurred to a farm off of Camp Rd, which was close to the beginning of the path. Mainly tree damage was noted along the rest of the path.
Large tree limb down on power line off of County Highway V.
Wind gust was estimated.
Trees and limbs down along Kiesling Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2021Every state in 2021This day in weather historyThe tornado archive for Wisconsin, 2021Warnings in Wisconsin, August 2021
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: 970690, 970548, 968787, 979424, 970549, 970683, 970691.