A trough of low pressure and unstable conditions resulted in clusters of thunderstorms across southern WI. A couple of storms produced damaging winds.
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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 MKX wrote it up.
A trough of low pressure and unstable conditions resulted in clusters of thunderstorms across southern WI. A couple of storms produced damaging winds.
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 Jun 20, 7:54 AM CST, 3 hours 6 minutes earlier.
Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 854 AM CDT Sat Jun 20 2020 .UPDATE... Bit of a lull in activity at this time, but shower and thunderstorm coverage should increase again late this morning into this afternoon, as moisture continues to stream north into the area, and a mid level shortwave approaches from the west. Overall expectations have not changed, with an isolated strong storm or two still possible. Most storms will just bring periods of moderate to heavy rain, though, given very high PWATs on the order of 1.7-1.8 inches, which are near record levels for this time of year. && .MARINE... Light to moderate southerly winds are expected today as low pressure lifts from southwestern Wisconsin today into southern Ontario by tomorrow morning. Southerly flow will continue tomorrow, before switching to a westerly direction for much of the coming workweek. && .PREV DISCUSSION... (Issued 557 AM CDT Sat Jun 20 2020) AVIATION(12Z TAFS)...VFR conditions will prevail for southern WI through most of the period. However progs are suggesting some MVFR ceilings/vsbys will are possible with any shra/tsra and also evolving closer to the boundary into the west and northern cwa today. Will have rounds of showers and thunderstorms affecting srn WI today into this evening as mid level waves ride northeast along and ahead of a lower level surface boundary. Activity could get underway early on this morning in parts of the western forecast area with an expansion eastward into the afternoon/evening hours. Some stronger storms are possible this afternoon and early this evening. PC PREV DISCUSSION... (Issued 245 AM CDT SAT JUN 20 2020) SHORT TERM... TODAY AND TONIGHT - Confidence...Medium. Warm, moist and moderately unstable airmass will be in place into this evening. Mid level flow will be southwest this period with two separate windows of energy coming through. A couple of weaker vort maxes swing through today with the primary wave arriving this evening. Weak surface low lifts north through the state with trailing trough into southern WI. Overall, CAMS not showing appreciable organization to the activity that essentially is hit or miss all day into the evening. Mid level lapse rates are weak with 0- 6km shear not ideal. So, some wind/hail potential this afternoon/early evening though expecting this activity to by and large remain below severe thresholds. Will continue the idea of gradually expanding the higher pops into the eastern cwa this afternoon/evening with higher pops earlier in the west. Went with a lowering pop trend overnight as surface forcing wanes/diurnal instability lowers and influence of the second wave lifts northeast of the area. SUNDAY THROUGH MONDAY - Confidence...Medium. A break from the showers is anticipated for most of Sunday into Sunday evening as short-wave ridging moves through the region. Sunshine should return, resulting in a nice final day of the weekend, with temperatures peaking in the low to mid 80s. The dry weather looks to be short-lived as the frontal boundary that sagged to the south of WI by early Sunday will begin moving back to the north Sunday night and Monday. The increasing low level southerly winds will be in response to strengthening low pressure in southern Canada, with a southerly extension into the northern Plains and Upper Midwest. Precipitable water returns to 1-1.5" by Monday morning ahead of several mid-level short wave trofs moving through WI Monday into Monday night. Will continue to carry likely and categorical pops for this period but there is one concern that may limit the showers and storms over the area. A secondary stronger short wave trof wl be moving across the central MS Valley region on Monday, which may limit some moisture return into the upper Midwest. Never the less, thinking enough moisture and synoptic lift will be farther north to bring at least scattered convection back to the area later Monday. Elevated instability should return to the 500-1500 j range with bulk shear of 30-40 kts. A few stronger storms will be possible with the initial moisture and warm air surge early Monday, with a better chance for more organized convection in the afternoon and evening as surface cold front moves through. Agree with Marginal Risk assessment at this point, and could be elevated to Slight in later periods. Can not rule out some slow-moving storms producing heavy rainfall at this point as Corfidi Vectors less than 10 kts much of this period. LONG TERM... MONDAY NIGHT THROUGH FRIDAY - Forecast Confidence...Medium. Extended guidance in reasonable agreement on persistent, slow-moving long wave trof over the Great lakes into southern Canada for much of this period. The latest GFS shows a more aggressive mid-level low pressure system digging south into Upper Michigan on Wednesday while other guidance keeps the low pressure center farther north in Canada. Thinking GFS an outlier at this point, but as short wave trofs continue to rotate around the Canadian low pressure, along with daytime instability, showers and a few storms will threaten southern WI most daytime periods from Tuesday through Friday. Persistent west to northwest winds will pull cooler air across the western Great Lakes during this period but likely not as cool as latest GFS deterministic guidance is showing. Comfortable temperatures are expected most days with highs in the 70s with a daytime lake breeze cooling shore areas a bit. Lake Michigan continues to warm off the southeast WI coast, with the surface water temp now in the low 60s. However a strong upwelling offshore wind event would cool the water significantly, mostly likely back into the low 50s. Fortunately, no events lie on the horizon. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && Update...Boxell Today/Tonight and Aviation/Marine...Boxell Sunday THROUGH Friday...99
Hazardous Weather Outlook National Weather Service Milwaukee/Sullivan WI 326 AM CDT Sat Jun 20 2020 WIZ046-047-051-052-056>060-062>072-210830- Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge- Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee- Lafayette-Green-Rock-Walworth-Racine-Kenosha- 326 AM CDT Sat Jun 20 2020 This Hazardous Weather Outlook is for portions of east central Wisconsin, south central Wisconsin and southeast Wisconsin. .DAY ONE...Today and Tonight Scattered thunderstorms will develop across the area later this morning, and continue to affect southern Wisconsin into this evening. The thunderstorms will be most numerous later this afternoon and evening. Cloud to ground lightning will accompany any thunderstorms. An isolated strong to severe thunderstorm may produce wind gusts to 60 mph and a few hail stones to 1 inch. Brief heavy rainfall will also accompany the thunderstorms, but flooding rainfall is not expected. .DAYS TWO THROUGH SEVEN...Sunday through Friday Thunderstorms chances return later Sunday night and Monday. A few strong to severe thunderstorms will be possible, mainly Monday afternoon and evening. Small chances for thunderstorms continue mainly during the daytime from Tuesday through Friday. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed this afternoon and evening, and again on Monday. LMZ643>646-210830- 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- 326 AM CDT Sat Jun 20 2020 This Hazardous Weather Outlook is for the nearshore waters from Sheboygan Wisconsin to Winthrop Harbor Illinois. .DAY ONE...Today and Tonight Scattered thunderstorms are expected to develop, mainly this afternoon and tonight. Cloud to ground lightning will accompany the thunderstorms. An isolated strong to severe storm may produce wind gusts to 50 knots and 1 inch hail. .DAYS TWO THROUGH SEVEN...Sunday through Friday Thunderstorms chances return later Sunday night and Monday. A few strong to severe thunderstorms will be possible, mainly Monday afternoon and evening. Small chances for thunderstorms continue mainly during the daytime from Tuesday through Friday. LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-210830- 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- 326 AM CDT Sat Jun 20 2020 This Hazardous Weather Outlook is for the open waters of Lake Michigan. .DAY ONE...Today and Tonight Scattered thunderstorms are expected to develop, mainly this into this evening. Cloud to ground lightning will accompany any thunderstorms. An isolated strong to severe thunderstorm may produce wind gusts to 50 knots and 1 inch hail, mainly over the southern Open Waters. There is a chance that dense fog may develop over portions of the Open Waters later tonight into Sunday. .DAYS TWO THROUGH SEVEN...Sunday through Friday Thunderstorms chances return later Sunday night and Monday. A few strong to severe thunderstorms will be possible, mainly Monday afternoon and evening. Small chances for thunderstorms continue mainly during the daytime from Tuesday through Friday. www.weather.gov/mkx MBK
Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
1130 AM CDT Sat Jun 20 2020
WIZ065-066-070>072-201715-
Walworth-Waukesha-Milwaukee-Racine-Kenosha-
...AN AREA OF STRONG THUNDERSTORMS WILL AFFECT SOUTHERN MILWAUKEE...
EAST CENTRAL WALWORTH...RACINE...SOUTHEASTERN WAUKESHA AND
NORTHWESTERN KENOSHA COUNTIES...
At 1127 AM CDT, strong thunderstorms were clustered over
northwestern Kenosha to east central Walworth counties, moving
northeast at 25 mph.
Winds of 30 to 40 mph and pea size hail are possible with these
storms.
Locations impacted include...
Milwaukee, Racine, West Allis, New Berlin, Brookfield, Greenfield,
Oak Creek, Mount Pleasant, Muskego, South Milwaukee, Cudahy,
Greendale, Hales Corners, Sturtevant, Elm Grove, Union Grove, Paddock
Lake, Wind Lake, Camp Lake and Rochester.
LAT...LON 4276 8777 4272 8777 4254 8815 4269 8842
4305 8811 4291 8784 4288 8785 4285 8782
4285 8783 4284 8781 4278 8775
TIME...MOT...LOC 1627Z 225DEG 22KT 4265 8808
WAGNERThe Milwaukee radar (KMKX), 45 km away, was scanning. The volume nearest the first event began at 16:57 UTC.
4 thunderstorm wind. Local standard time, as filed.
Numerous branches and trees down in the area.
Numerous reports of branches and trees down in the area.
Several large tree limbs knocked down in the Bay View neighborhood.
Multiple reports of branches and trees down in the Township of Springvale.
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, June 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: 899250, 899251, 899252, 899254.