The Memorial Day holiday became turbulent during the late afternoon and evening hours as a line of severe thunderstorms ahead of a cold front crossed southern Wisconsin, producing damaging winds gusts and large hail up to 1.25 inches in diameter. An unstable air mass was in place, with high temperatures in the upper 80s to around 90, and dew points in the lower 60s, that produced mixed-layer CAPE values of 1000-1800 J/kg, with forcing along the front enhanced by weak upper level divergence and weak differential vorticity advection. While directional shear was minimal, with above-surface winds unidirectional from the west, there was sufficient speed shear to support organized updrafts, and for the individual cells to merge into bowing line segments. Numerous reports of downed trees and power lines were received, as well as some minor structural damage. There were also many large hail reports, mainly along and south of a line from northern Sauk County, near Reedsburg and the Wisconsin Dells, to northern Ozaukee County near Port Washington. Fire officials in Edgerton, in northeast Rock County, and in the city of Jackson in Washington County reported structural fires caused by lightning strikes.

Thunderstorm Wind in WAUKESHA, WISCONSIN
From 28-MAY-12 17:35:00 to 28-MAY-12 17:35:00 (CST-6)
Location: STONEBANK
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Public

Large pine trees were reported to be blown down by powerful thunderstorm winds by the public in Stone Bank.

Thunderstorm Wind in WASHINGTON, WISCONSIN
From 28-MAY-12 17:37:00 to 28-MAY-12 17:37:00 (CST-6)
Location: COLGATE
Magnitude: 61.00 EG
Property damage: 10.00K
Reported by: Public

Winds from a gustnado damaged the soffit on a home, felled trees and damaged fencing  as reported by the public 3 miles west of Colgate.

Thunderstorm Wind in MARQUETTE, WISCONSIN
From 28-MAY-12 15:36:00 to 28-MAY-12 15:36:00 (CST-6)
Location: MONTELLO
Magnitude: 65.00 EG
Property damage: 20.00K
Reported by: Trained Spotter

A trained spotter reported many trees and power lines downed by powerful thunderstorm wind gusts, estimated up to 75 mph (65 knots) in Montello. Metal shingles were torn off of a barn roof.

Thunderstorm Wind in GREEN, WISCONSIN
From 28-MAY-12 16:10:00 to 28-MAY-12 16:10:00 (CST-6)
Location: NEW GLARUS
Magnitude: 74.00 EG
Property damage: 30.00K
Reported by: Trained Spotter

A trained spotter reported trees and power lines downed by powerful thunderstorm wind gusts estimated at 80 mph (74 knots) in the town of New Glarus. One car was totally damaged when struck by a falling tree, with roof shingles blown off several homes.

Thunderstorm Wind in GREEN, WISCONSIN
From 28-MAY-12 16:15:00 to 28-MAY-12 16:20:00 (CST-6)
Location: DAYTON
Magnitude: 74.00 EG
Property damage: 30.00K
Reported by: Trained Spotter

A trained spotter reported trees and power lines downed by powerful thunderstorm wind gusts estimated at 80 mph (74 knots) in a swath from from 2 miles north of Dayton to Dayton. Roof shingles were blown off several homes.

Thunderstorm Wind in GREEN, WISCONSIN
From 28-MAY-12 16:15:00 to 28-MAY-12 16:20:00 (CST-6)
Location: DAYTON
Magnitude: 70.00 EG
Property damage: 10.00K
Reported by: Emergency Manager

The Green County Emergency Manager reported shingles were blown off several homes by severe thunderstorm winds 2 miles north of Dayton.

Thunderstorm Wind in DANE, WISCONSIN
From 28-MAY-12 16:15:00 to 28-MAY-12 16:15:00 (CST-6)
Location: MSN MOREY FLD ARPT
Magnitude: 50.00 MG
Property damage: 2.00K
Reported by: AWOS

Thunderstorm Wind in ROCK, WISCONSIN
From 28-MAY-12 16:44:00 to 28-MAY-12 16:44:00 (CST-6)
Location: EVANSVILLE
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Trained Spotter

A trained spotter reported trees were downed by severe thunderstorm winds in the town of Evansville.

Hail in DANE, WISCONSIN
From 28-MAY-12 16:38:00 to 28-MAY-12 16:38:00 (CST-6)
Location: STOUGHTON
Magnitude: 0.75 
Reported by: Public

Thunderstorm Wind in DANE, WISCONSIN
From 28-MAY-12 16:27:00 to 28-MAY-12 16:27:00 (CST-6)
Location: OREGON
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Public

The public reported trees were knocked down by severe thunderstorm winds 2 miles east of Oregon.

Hail in COLUMBIA, WISCONSIN
From 28-MAY-12 15:00:00 to 28-MAY-12 15:10:00 (CST-6)
Location: WISCONSIN DELLS
Magnitude: 1.25 
Property damage: 5.00K
Reported by: Trained Spotter

A ten-minute shower of large hail from a severe thunderstorm broke windows, with the damage totaling $5,000.

Hail in MARQUETTE, WISCONSIN
From 28-MAY-12 15:20:00 to 28-MAY-12 15:20:00 (CST-6)
Location: BRIGGSVILLE
Magnitude: 1.75 
Reported by: Amateur Radio

Hail in MARQUETTE, WISCONSIN
From 28-MAY-12 15:36:00 to 28-MAY-12 15:36:00 (CST-6)
Location: MONTELLO
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in DANE, WISCONSIN
From 28-MAY-12 16:09:00 to 28-MAY-12 16:09:00 (CST-6)
Location: MIDDLETON
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in GREEN LAKE, WISCONSIN
From 28-MAY-12 15:50:00 to 28-MAY-12 15:50:00 (CST-6)
Location: MARQUETTE
Magnitude: 1.00 
Reported by: Trained Spotter

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 28-MAY-12 17:50:00 to 28-MAY-12 17:50:00 (CST-6)
Location: PALMYRA
Magnitude: 52.00 EG
Property damage: 3.00K
Reported by: NWS Employee

Large tree branches, up to 12 inches in diameter, were broken off and blown 50 feet by powerful thunderstorm wind gusts about 1.5 miles southwest of Palmyra on Blue Spring Lake.

Thunderstorm Wind in WAUKESHA, WISCONSIN
From 28-MAY-12 18:13:00 to 28-MAY-12 18:13:00 (CST-6)
Location: DOWNTOWN WAUKESHA
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Public

The public reported trees downed by powerful thunderstorm winds 2 miles southwest of the city of Waukesha.

Hail in ROCK, WISCONSIN
From 28-MAY-12 16:50:00 to 28-MAY-12 16:50:00 (CST-6)
Location: EVANSVILLE
Magnitude: 0.75 
Reported by: Public

Hail in DANE, WISCONSIN
From 28-MAY-12 16:54:00 to 28-MAY-12 16:54:00 (CST-6)
Location: STOUGHTON
Magnitude: 1.00 
Reported by: Public

Thunderstorm Wind in WASHINGTON, WISCONSIN
From 28-MAY-12 17:45:00 to 28-MAY-12 17:45:00 (CST-6)
Location: GERMANTOWN
Magnitude: 56.00 EG
Property damage: 10.00K
Reported by: Public

Tress and power lines were reported to be blown down by powerful thunderstorm winds by the public in Germantown.

Thunderstorm Wind in WAUKESHA, WISCONSIN
From 28-MAY-12 18:22:00 to 28-MAY-12 18:22:00 (CST-6)
Location: NEW BERLIN
Magnitude: 52.00 EG
Property damage: 20.00K
Reported by: Public

The public reported trees downed by powerful thunderstorm winds 2 miles southeast of the city of New Berlin. A tree measuring 15 inches in diameter fell on a house.

Lightning in ROCK, WISCONSIN
From 28-MAY-12 18:25:00 to 28-MAY-12 18:25:00 (CST-6)
Location: EDGERTON
Property damage: 75.00K
Reported by: Fire Department/Rescue

Fire officials say lightning ignited a fire that damaged a 21-unit senior living facility in Edgerton, displacing 30 residents.

Hail in WAUKESHA, WISCONSIN
From 28-MAY-12 17:35:00 to 28-MAY-12 17:35:00 (CST-6)
Location: STONEBANK
Magnitude: 0.88 
Reported by: Public

Thunderstorm Wind in OZAUKEE, WISCONSIN
From 28-MAY-12 17:54:00 to 28-MAY-12 17:54:00 (CST-6)
Location: CEDARBURG
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Public

Tress and power lines were reported to be blown down by powerful thunderstorm winds by the public in Cedarburg.

Thunderstorm Wind in COLUMBIA, WISCONSIN
From 28-MAY-12 15:04:00 to 28-MAY-12 15:10:00 (CST-6)
Location: WISCONSIN DELLS
Magnitude: 65.00 EG
Property damage: 30.00K
Reported by: Law Enforcement

Law enforcement officials reported many trees and power lines downed by powerful thunderstorm wind gusts, estimated up to 75 mph (65 knots) in the Wisconsin Dells. Four cars were also damaged, with overall property damages estimated to be $30,000 dollars.

Thunderstorm Wind in ROCK, WISCONSIN
From 28-MAY-12 16:35:00 to 28-MAY-12 16:35:00 (CST-6)
Location: COOKSVILLE
Magnitude: 65.00 EG
Property damage: 5.00K
Reported by: Emergency Manager

The Rock County Emergency Manager reported trees were downed by severe thunderstorm winds in the village of Cooksville.

Thunderstorm Wind in MARQUETTE, WISCONSIN
From 28-MAY-12 15:15:00 to 28-MAY-12 15:17:00 (CST-6)
Location: BRIGGSVILLE
Magnitude: 74.00 EG
Property damage: 20.00K
Reported by: Fire Department/Rescue

Fire department officials reported many trees and power lines downed by powerful thunderstorm wind gusts, estimated up to 85 mph (74 knots) in Briggsville. Tree debris damaged several cars, with roof damage to several homes.

Lightning in OZAUKEE, WISCONSIN
From 28-MAY-12 18:50:00 to 28-MAY-12 18:50:00 (CST-6)
Location: CEDARBURG
Property damage: 20.00K
Reported by: Law Enforcement

The Ozaukee County Sheriff Department reported a fire ignited by a lightning strike in the 3200 block of Twin Creeks Road in the town of Cedarburg.

Thunderstorm Wind in GREEN, WISCONSIN
From 28-MAY-12 17:08:00 to 28-MAY-12 17:08:00 (CST-6)
Location: BRODHEAD
Magnitude: 65.00 EG
Property damage: 100.00K
Reported by: Emergency Manager

The Green County Emergency Manager reported $100,000 of damage from severe thunderstorm winds 4 miles southwest of Brodhead. The damage included 2 barns/sheds with one losing it's roof to the powerful winds. The severe winds peeled siding off of one home, and broke windows and pushed in the door on another home.

Hail in SAUK, WISCONSIN
From 28-MAY-12 14:44:00 to 28-MAY-12 14:45:00 (CST-6)
Location: REEDSBURG
Magnitude: 1.25 
Reported by: Trained Spotter

Thunderstorm Wind in GREEN LAKE, WISCONSIN
From 28-MAY-12 16:50:00 to 28-MAY-12 16:50:00 (CST-6)
Location: MARQUETTE
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Trained Spotter

A trained spotter reported trees downed by powerful thunderstorm wind gusts estimated at 65 mph (56 knots) in the village of Marquette.

Hail in OZAUKEE, WISCONSIN
From 28-MAY-12 17:59:00 to 28-MAY-12 17:59:00 (CST-6)
Location: CEDARBURG
Magnitude: 1.25 
Reported by: Public

A report from the public via Twitter stated 1.25 inch diameter hail fell in Cedarburg.