Two rounds of thunderstorms affected southern Wisconsin on April 3rd, as low pressure moved northeast from Iowa across Wisconsin. Morning elevated thunderstorms, with warm air advection on the nose of a low-level jet ahead of the approaching low, did not produce severe weather...but a shower of small hail created icy road conditions in Dodge County, where a two-vehicle accident killed a 26 year old female and injured two others. During the afternoon hours, a warm front lifted into southern Wisconsin as the low moved into the state...with mean layer CAPE increasing to 1000 to 1500 J/kg along with strong low layer shear and deep layer bulk shear. This triggered the second round of thunderstorms in the evening that were severe, producing mainly large hail up to the size of a baseballs, along with damaging winds. Madison-based American Family Insurance Company reported 375 property claims as well as 200 vehicle damage claims in Dane and Dodge counties alone.  There were probably more damaged vehicles that weren't reported to insurance companies. Roof damage caused by the golf ball to baseball-sized hail was extensive in the western suburbs of Madison, with some homes and businesses requiring whole-roof replacements. It was not possible to break up the insurance company claims and assign monetary losses to individual storms.  Total monetary losses were probably in the low millions of dollars.

Hail in LAFAYETTE, WISCONSIN
From 03-APR-11 19:55:00 to 03-APR-11 19:55:00 (CST-6)
Location: BELMONT
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in COLUMBIA, WISCONSIN
From 03-APR-11 21:15:00 to 03-APR-11 21:15:00 (CST-6)
Location: FALL RIVER
Magnitude: 1.00 
Reported by: Public

Hail in DANE, WISCONSIN
From 03-APR-11 20:20:00 to 03-APR-11 20:25:00 (CST-6)
Location: MT HOREB
Magnitude: 1.75 
Reported by: Amateur Radio

Hail in LAFAYETTE, WISCONSIN
From 03-APR-11 20:50:00 to 03-APR-11 20:50:00 (CST-6)
Location: GRATIOT
Magnitude: 1.75 
Reported by: Law Enforcement

Hail in DODGE, WISCONSIN
From 03-APR-11 22:04:00 to 03-APR-11 22:04:00 (CST-6)
Location: WATERTOWN
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in DANE, WISCONSIN
From 03-APR-11 20:51:00 to 03-APR-11 20:51:00 (CST-6)
Location: MIDDLETON
Magnitude: 2.50 
Reported by: Public

Hail in JEFFERSON, WISCONSIN
From 03-APR-11 21:20:00 to 03-APR-11 21:20:00 (CST-6)
Location: LAKE MILLS
Magnitude: 0.88 
Reported by: Public

Hail in DANE, WISCONSIN
From 03-APR-11 20:33:00 to 03-APR-11 20:33:00 (CST-6)
Location: MIDDLETON
Magnitude: 2.50 
Reported by: Amateur Radio

Hail in DANE, WISCONSIN
From 03-APR-11 20:30:00 to 03-APR-11 20:30:00 (CST-6)
Location: MIDDLETON
Magnitude: 2.00 
Reported by: Amateur Radio

Hail in DANE, WISCONSIN
From 03-APR-11 20:35:00 to 03-APR-11 20:35:00 (CST-6)
Location: MIDDLETON
Magnitude: 2.75 
Reported by: Trained Spotter

Hail in DANE, WISCONSIN
From 03-APR-11 20:38:00 to 03-APR-11 20:45:00 (CST-6)
Location: CAMP RANDALL STADIUM
Magnitude: 1.75 
Reported by: Broadcast Media

Hail in DANE, WISCONSIN
From 03-APR-11 20:39:00 to 03-APR-11 20:39:00 (CST-6)
Location: MONONA
Magnitude: 2.00 
Reported by: Amateur Radio

Hail in DANE, WISCONSIN
From 03-APR-11 20:55:00 to 03-APR-11 20:55:00 (CST-6)
Location: DE FOREST
Magnitude: 1.75 
Reported by: Public

Hail in DANE, WISCONSIN
From 03-APR-11 20:45:00 to 03-APR-11 20:45:00 (CST-6)
Location: CAMP RANDALL STADIUM
Magnitude: 1.75 
Reported by: Public

Thunderstorm Wind in DODGE, WISCONSIN
From 04-APR-11 00:15:00 to 04-APR-11 00:21:00 (CST-6)
Location: IRON RIDGE
Magnitude: 70.00 EG
Reported by: Trained Spotter

Trees were blown down, shingles were torn off roofs and a corn crib was blown over by thunderstorm winds estimated at 80 mph (70 knots). This Dodge Count damage swath continued into Washington County and ended in West Bend. Collectively the damage swath was roughly 14 miles long.  The width of the damage swatch was about 2 miles.

Thunderstorm Wind in WASHINGTON, WISCONSIN
From 04-APR-11 00:21:00 to 04-APR-11 00:33:00 (CST-6)
Location: NENNO
Magnitude: 70.00 EG
Reported by: Trained Spotter

Trees were blown down and shingles were torn off roofs by thunderstorm winds estimated at 80 mph (70 knots). This Washington County damage swath actually started in Dodge County about 4 miles northeast of Iron Ridge.  The entire damage swatch stretched for roughly 14 miles and had a width of about 2 miles.

Hail in DODGE, WISCONSIN
From 03-APR-11 10:35:00 to 03-APR-11 10:40:00 (CST-6)
Location: BEAVER DAM
Magnitude: 0.75 
Property damage: 12.00K
Reported by: Newspaper

A shower of 3/4 inch hail produced icy roads that caused a two-vehicle accident on State Highway 151 north of State Highway 33, north of Beaver Dam. A 26-year-old Green Bay woman was killed, and the male drivers of the two vehicles were injured.

Hail in LAFAYETTE, WISCONSIN
From 03-APR-11 19:55:00 to 03-APR-11 19:55:00 (CST-6)
Location: DARLINGTON
Magnitude: 1.75 
Reported by: Law Enforcement