A severe thunderstorm developed on the lake breeze front and produced wind damage from Brookfield to New Berlin in eastern Waukesha County.
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 severe thunderstorm developed on the lake breeze front and produced wind damage from Brookfield to New Berlin in eastern Waukesha County.
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 23, 1:20 PM CST, 4 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 220 PM CDT Sun Aug 23 2020 .SHORT TERM... (Issued 220 PM CDT Sun Aug 23 2020) Tonight through Monday: Visible satellite loop shows CU field percolating a bit ahead of weak surface/925 trough axis. MLCAPE values are 1000-1500 j/kg with some moisture convergence noted. So will keep mention of mainly isolated activity going into the early evening hours with the best chance in the far eastern cwa. After passage of weak trough this evening, weak high pressure and DAVA should prevail. This should result in quiet conditions into Monday. There is an evolving 850/925 waa regime that will result in building heat and a nudge upward in dew points into Monday. The primary baroclinicity should reside to our north. This should focus the storms. With 925/850 temps on the rise would expect highs to reach near 90 for many areas with the dew points around 70. Monday night: With some mid level energy riding along baroclinic zone to the north of us we will likely see an MCS form and then track ese towards srn WI during this period. At this time have the highest pops in the north, trailing off a bit into the far south. Per SWODY2, some severe potential with this activity. Gusty winds/hail the likely threats. Not all models bring this all the way into southern WI, so some uncertainty remains, though highest confidence at the moment would be more in our north towards central WI. However these, MCS's more of ten than not, like to track farther than we think, so we shall see and adjust pops accordingly as we draw closer. Collar && .LONG TERM... (Issued 220 PM CDT Sun Aug 23 2020) Tuesday through Sunday: A MCS may linger just beyond 12Z Tue over srn WI. Otherwise, weak warm, moist advection will continue ahead of the approaching upper ridge axis, but stronger forcing will be well north for Tue nt- Wed. The upper ridging will flatten as it shifts across the area on Wed but a cap should build in. Hot and humid conditions are expected and will continue into Thu. A broad upper upper trough and wnwly flow will then return for Thu nt-Fri along with the passage of its cool front. Another round or two of convection is expected. A ridge of high pressure will then shift ewd across WI for Sat-Sat nt with a pleasant airmass in place for the weekend. Gehring && .AVIATION... (Issued 220 PM CDT Sun Aug 23 2020) VFR this period with weak trough passing through to the east of the area this evening. Will have to keep an eye on any isolated showers or thunderstorms that may develop in the peak heating ahead of the boundary. This would occur mainly in far eastern WI from mid afternoon through early evening. Coverage looks quite spotty at this point. Otherwise and continued VFR overnight into Monday. Collar && .MARINE... (Issued 220 PM CDT Sun Aug 23 2020) A ridge of high pressure will build into Lake MI for Monday. Low pressure and a frontal boundary will bring the threat of storms to the Lake area from late Monday into Tuesday. Some stronger storms are possible, especially in central and southern sections Monday night into Tuesday. Collar && .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 303 PM CDT Sun Aug 23 2020 WIZ046-047-051-052-056>060-062>072-242015- Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge- Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee- Lafayette-Green-Rock-Walworth-Racine-Kenosha- 303 PM CDT Sun Aug 23 2020 This Hazardous Weather Outlook is for portions of east central Wisconsin, south central Wisconsin and southeast Wisconsin. .DAY ONE...Tonight A few thunderstorms will be possible into early this evening in far eastern Wisconsin. .DAYS TWO THROUGH SEVEN...Monday through Sunday Heat indices will be in the mid 90s Monday through Wednesday. There will be a chance for thunderstorms Monday evening through Tuesday. A few strong storms will be possible during this time. Additional thunderstorm chances are expected for Thursday and Friday with a small chance on Sunday. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. LMZ643>646-242015- 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- 303 PM CDT Sun Aug 23 2020 This Hazardous Weather Outlook is for the nearshore waters from Sheboygan Wisconsin to Winthrop Harbor Illinois. .DAY ONE...Tonight A few thunderstorms will be possible into early this evening. .DAYS TWO THROUGH SEVEN...Monday through Sunday There will be a chance for thunderstorms Monday evening through Tuesday. A few strong storms will be possible during this time. Additional thunderstorm chances are expected for Thursday and Friday. LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-242015- 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- 303 PM CDT Sun Aug 23 2020 This Hazardous Weather Outlook is for the open waters of Lake Michigan. .DAY ONE...Tonight A few thunderstorms will be possible through early this evening. .DAYS TWO THROUGH SEVEN...Monday through Sunday Periodic chances for storms will continue across the northern portion of Lake Michigan for much of the week. Chances will expand to include the southern portion of the lake Monday night and Tuesday, and again late in the week. Collar www.weather.gov/mkx
Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
611 PM CDT Sun Aug 23 2020
WIZ065-066-232345-
Waukesha-Milwaukee-
...A STRONG THUNDERSTORM WILL AFFECT NORTHERN MILWAUKEE AND
NORTHEASTERN WAUKESHA COUNTIES...
At 610 PM CDT, a strong thunderstorm was located over northwestern
Milwaukee, moving south at 5 mph.
Winds of 30 to 40 mph and nickel size hail are possible with this
storm.
Locations impacted include...
Milwaukee, Waukesha, West Allis, Wauwatosa, New Berlin, Brookfield,
Menomonee Falls, Whitefish Bay, Pewaukee, Brown Deer, Sussex, Fox
Point, Elm Grove, West Milwaukee, Glendale, Butler, River Hills,
Lannon, Shorewood and Marquette University.
If outdoors, consider seeking shelter inside a building.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 4305 8789 4303 8790 4302 8790 4301 8789
4298 8821 4319 8819 4319 8793 4312 8790
4307 8787
TIME...MOT...LOC 2310Z 352DEG 4KT 4313 8805
DDVSpecial Weather Statement National Weather Service Milwaukee/Sullivan WI 643 PM CDT Sun Aug 23 2020 WIZ065-066-240015- Waukesha-Milwaukee- ...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN MILWAUKEE AND EAST CENTRAL WAUKESHA COUNTIES... At 643 PM CDT, a strong thunderstorm was located over Elm Grove, moving south at 15 mph. Winds of 30 to 40 mph and nickel size hail are possible with this storm. Locations impacted include... Milwaukee, Waukesha, West Allis, Wauwatosa, New Berlin, Brookfield, Greenfield, Menomonee Falls, Muskego, Greendale, Pewaukee, Hales Corners, Elm Grove, Franklin, Butler, State Fair Park and Milwaukee Co Zoo. If outdoors, consider seeking shelter inside a building. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. LAT...LON 4312 8815 4309 8798 4290 8801 4295 8829 TIME...MOT...LOC 2343Z 019DEG 11KT 4303 8811 DDV
The Milwaukee radar (KMKX), 36 km away, was scanning. The volume nearest the first event began at 23:42 UTC.
1 thunderstorm wind. Local standard time, as filed.
Multiple trees and some wires down across Brookfield and New Berlin.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2020Every state in 2020This day in weather historyWarnings in Wisconsin, August 2020
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: 905006.