Several severe thunderstorms impacted portions of southern Wisconsin, especially near Lake Michigan as storms developed across central Wisconsin and eventually morphed into a line that dropped south into Illinois.
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.
Several severe thunderstorms impacted portions of southern Wisconsin, especially near Lake Michigan as storms developed across central Wisconsin and eventually morphed into a line that dropped south into Illinois.
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 6, 1:25 PM CST, 2 hours 3 minutes earlier.
Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 225 PM CDT Fri Aug 6 2021 .SHORT TERM... (Issued 225 PM CDT Fri Aug 6 2021) Tonight: An MCV moving through southern WI triggering mainly isolated t-storms in very moist and unstable airmass. This feature will gradually pull out of southeast WI later this evening. Until then expect to see sct t-storms. The 0-6km shear is weak and mid level lapse rates are poor, so not expecting any real organization/severe threat with any of these. So will keep the pops going for a while this evening. Some weak isentropic ascent later in the night may lead to some isolated development in the far western cwa. Overall mid level ridging will build across the area in the wake of the MCV. High pressure nosing in from the north may push a frontal boundary southward into the cwa later tonight. Saturday through Saturday night: The frontal boundary will likely turn around and head back north as a warm front and potentially serve as a focus for rounds of storms this period. Noticing some 925/850 millibar baroclinicity which gradually lifts northward this period. So after some morning weaker activity may see an afternoon round move through in conjunction with a wave riding the ridging and in proximity to the lower level frontogenesis. As we head into Saturday night the focus may lift largely to our north and northwest in better proximity to the axis of approaching southerly LLJ and where this impinges on the 925/850 baroclinicity. && .LONG TERM... (Issued 225 PM CDT Fri Aug 6 2021) Sunday through Friday: Main focus is on convective trends for Sunday and how that setup will pan out. Beyond that, it looks to remain hot and humid with another shot for convection Tuesday night into early Wednesday. Going into Sunday, models are fairly consistent with showing a 500mb trough digging east/northeastward across the Central Plains and becoming centered over Iowa by mid afternoon Sunday. The trough appears to slow down a bit as it gets further away from the stronger mid level flow to the northwest and ahead of the next closed trough in the Pacific NW. Mid level winds ahead of this trough aren't screaming but do increase to around 25-35kts which should help with increasing the deep layer shear. Further down around 850-925mb, the low level flow does appear to be increasing into the evening hours with PW values getting up around 1.5". At the surface, appears the main low will track across mid Minnesota with a warm front extending east of it into central Wisconsin. The main outlier guidance-wise appears to be the 06.12z GFS which just doesn't seem to figure out how to resolve everything going on with the setup. If the 06.12z NAM pans out, there'll be an initial round of scattered convection that comes through in the afternoon on a lead shortwave trough/WAA before the better environment moves in ahead of the trough/low for Sunday evening/overnight. NAM soundings show a fat CAPE profile of around 4,000 J/kg with most of the wind shear being in the lowest 3km with south winds at 15kt at the surface going to 40-45kt and westerly at 700mb. With the nose of the LLJ poking into eastern Iowa/southeast Minnesota/western Wisconsin, it appears that an MCS will develop in that region and then race eastward across southern Wisconsin into the overnight hours. The 06.12z ECMWF appears to focus a bit further south with the evening convection while the GFS not close to any of these solutions. As previously mentioned, with the decent 0-3km shear in place, can't rule out some QLCS mesovort potential on this one. Expect there'll be some heavy rain as well, but think that this focus will be on wherever the nose of the LLJ sets up in the evening. Beyond this, we stay in southwesterly flow aloft, so should stay warm and humid through much of the week. There is a hint of a cold front coming in next weekend some time, but the guidance has been slowing this feature down with each run. Precipitation/convection-wise, the next feature of note comes in Tuesday night into Wednesday with another mid level closed low/trough that runs through southern Canada. Have kept precipitation chances a bit higher in that period to account for that feature coming through. Halbach && .AVIATION... (Issued 225 PM CDT Fri Aug 6 2021) MCV pivoting through srn WI generating a few tsra into the mid evening hours. Organization looks unlikely given unfavorable shear environment. Lingering IFR cigs across parts of SC WI should improve once MCV clears that area. Otherwise a fairly widespread MVFR CU field in place ahead of the feature. After the MCV moves through things look largely quiet overnight. High pressure nudging in from the north may drop a frontal boundary into the area after midnight. Later tonight there may be a few shra or isold tsra in the far western sections due to renewed isentropic forcing there. Additional tsra may develop Saturday with the front retreating northward along with some mid level energy. && .MARINE... (Issued 225 PM CDT Fri Aug 6 2021) The pressure gradient has tightened up a bit across the lake ahead of a trough. This has resulted in an uptick in southerly winds. The trough will continue to slide east and winds will gradually weaken tonight into Saturday. Winds are expected to pick back up for Sunday as a stronger systems works its way into the Upper Midwest. Then the elevated winds look to continue into early next week. Otherwise, there will be daily thunderstorm chances today through early next week as multiple upper-level disturbances track across the western Great Lakes Region. && .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 143 PM CDT Fri Aug 6 2021 WIZ046-047-051-052-056>060-062>072-071845- Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge- Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee- Lafayette-Green-Rock-Walworth-Racine-Kenosha- 143 PM CDT Fri Aug 6 2021 This Hazardous Weather Outlook is for portions of east central Wisconsin, south central Wisconsin and southeast Wisconsin. .DAY ONE...Tonight A few thunderstorms are possible into the evening hours. .DAYS TWO THROUGH SEVEN...Saturday through Friday Chances for thunderstorms continue Saturday through early next week with stronger storms possible Saturday and 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>646-071845- 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- 143 PM CDT Fri Aug 6 2021 This Hazardous Weather Outlook is for the nearshore waters from Sheboygan Wisconsin to Winthrop Harbor Illinois. .DAY ONE...Tonight A few thunderstorms are possible this evening. .DAYS TWO THROUGH SEVEN...Saturday through Friday There will be chances of thunderstorms Saturday through early next week. LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-071845- 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- 143 PM CDT Fri Aug 6 2021 This Hazardous Weather Outlook is for the open waters of Lake Michigan. .DAY ONE...Tonight A few thunderstorms are possible this evening. .DAYS TWO THROUGH SEVEN...Saturday through Friday Chances of thunderstorms continue Saturday through early next week. www.weather.gov/mkx
Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
306 PM CDT Fri Aug 6 2021
WIZ051-052-062030-
Sheboygan WI-Fond Du Lac WI-
306 PM CDT Fri Aug 6 2021
...A strong thunderstorm will impact portions of northeastern Fond du
Lac and northwestern Sheboygan Counties through 330 PM CDT...
At 306 PM CDT, Doppler radar was tracking a strong thunderstorm near
St Anna, or 13 miles northeast of Fond Du Lac, moving east at 15 mph.
HAZARD...Winds in excess of 30 mph and half inch 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...
Elkhart Lake, Mount Calvary, St. Cloud, Calvary, Marytown, Johnsburg,
Pipe and Town of Forest.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4389 8816 4389 8792 4383 8789 4379 8825
4391 8834 4394 8827 4394 8817
TIME...MOT...LOC 2006Z 247DEG 15KT 4386 8820
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH
HANSENSpecial Weather Statement
National Weather Service Milwaukee/Sullivan WI
344 PM CDT Fri Aug 6 2021
WIZ052-062115-
Sheboygan WI-
344 PM CDT Fri Aug 6 2021
...A strong thunderstorm will impact portions of northeastern
Sheboygan County through 415 PM CDT...
At 344 PM CDT, Doppler radar was tracking a strong thunderstorm over
Howards Grove, moving east at 10 mph.
HAZARD...Winds in excess of 30 mph and penny 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...
Sheboygan, Howards Grove and Haven.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4376 8770 4376 8782 4389 8791 4389 8774
4385 8773 4381 8773 4377 8770
TIME...MOT...LOC 2044Z 253DEG 9KT 4383 8778
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...30 MPH
HANSENThe Green Bay radar (KGRB), 83 km away, was scanning. The volume nearest the first event began at 21:30 UTC.
3 thunderstorm wind, 2 hail. Local standard time, as filed.
Wind gust of 63 mph measured at the Sheboygan County Memorial Airport ASOS. Reports of tree damage around Plymouth into Sheboygan as well.
Hail reported to be 1 to 1.5 inch in diamater.
Tree down on a house per broadcast media.
Several large tree limbs downed. Medium size tree down in Fitchburg.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2021Every state in 2021This day in weather historyWarnings 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: 968784, 968786, 968788, 970688, 968785.