A deep 500 mb low and associated surface low pressure tracked from eastern South Dakota into central Minnesota, lifting a warm front into Wisconsin during the early afternoon of May 22nd. Cool 500 mb temperatures and moist surface dew points in the lower 60s produced sufficient instability for thunderstorm development, with mean-layer CAPE of 2000 to 2500 J/KG. A mid-level jet streak of 50-60 knots produced 40-50 knots of deep-layer wind shear for supercell thunderstorm development, with low-level shear of 30 to 40 knots in the 0-1 km layer as a low-level jet strengthened enhancing the tornado potential, especially near the warm front.

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 22-MAY-11 16:52:00 to 22-MAY-11 16:54:00 (CST-6)
Location: WATERTOWN
Magnitude: 56.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Newspaper

Numerous trees and power lines were reported blown down by damaging thunderstorm wind gusts estimated at 56 knots in a swath from 2 miles south of Watertown to Watertown. A tree fell on a home, with minimal damage reported by firefighters responding to the scene. The winds blew over a shed that damaged fencing, a viewing platform and a horse trailer at the Avalon Therapeutic Equestrian Center. Damage in the area totaled $50,000 dollars.

Hail in JEFFERSON, WISCONSIN
From 22-MAY-11 16:50:00 to 22-MAY-11 16:56:00 (CST-6)
Location: WATERTOWN
Magnitude: 1.75 
Reported by: NWS Employee

Hail in DODGE, WISCONSIN
From 22-MAY-11 16:36:00 to 22-MAY-11 16:36:00 (CST-6)
Location: CLYMAN
Magnitude: 1.00 
Reported by: Amateur Radio

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 22-MAY-11 16:55:00 to 22-MAY-11 17:00:00 (CST-6)
Location: FT ATKINSON
Magnitude: 50.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Mesonet

Trees and power lines were reported blown down by damaging thunderstorm wind gusts measured at 50 knots (58 mph) in a swath from Ft. Atkinson to Jefferson.

Hail in MARQUETTE, WISCONSIN
From 22-MAY-11 14:05:00 to 22-MAY-11 14:05:00 (CST-6)
Location: WESTFIELD
Magnitude: 4.25 
Reported by: Fire Department/Rescue

Hail in ROCK, WISCONSIN
From 22-MAY-11 16:51:00 to 22-MAY-11 16:51:00 (CST-6)
Location: MILTON
Magnitude: 0.75 
Reported by: NWS Employee

Hail in MARQUETTE, WISCONSIN
From 22-MAY-11 14:10:00 to 22-MAY-11 14:10:00 (CST-6)
Location: WESTFIELD
Magnitude: 2.75 
Reported by: Public

Hail in MARQUETTE, WISCONSIN
From 22-MAY-11 14:20:00 to 22-MAY-11 14:20:00 (CST-6)
Location: NESHKORO
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in GREEN LAKE, WISCONSIN
From 22-MAY-11 14:38:00 to 22-MAY-11 14:38:00 (CST-6)
Location: PRINCETON
Magnitude: 1.75 
Reported by: Law Enforcement

Thunderstorm Wind in ROCK, WISCONSIN
From 22-MAY-11 18:05:00 to 22-MAY-11 18:05:00 (CST-6)
Location: BELOIT
Magnitude: 52.00 MG
Reported by: Amateur Radio

A ham radio operator reported severe thunderstorm wind gusts that downed trees and tree limbs along a line from near Beloit to Afton. The downed trees blocked Findley Road for a time.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 22-MAY-11 18:40:00 to 22-MAY-11 18:40:00 (CST-6)
Location: LYONS
Magnitude: 56.00 EG
Reported by: Newspaper

A severe thunderstorm produced damaging wind gusts that downed trees in the town of Lyons, including a large maple tree that was estimated to be 235 years old, the oldest tree in Walworth County.

Hail in GREEN LAKE, WISCONSIN
From 22-MAY-11 14:22:00 to 22-MAY-11 14:22:00 (CST-6)
Location: PRINCETON
Magnitude: 1.75 
Reported by: Law Enforcement

Hail in DANE, WISCONSIN
From 22-MAY-11 15:45:00 to 22-MAY-11 15:45:00 (CST-6)
Location: (MSN)TRUAX FLD MADIS
Magnitude: 0.75 
Reported by: Trained Spotter

Hail in DANE, WISCONSIN
From 22-MAY-11 15:50:00 to 22-MAY-11 16:10:00 (CST-6)
Location: SUN PRAIRIE
Magnitude: 1.75 
Reported by: Amateur Radio

Ham radio operators reported severe thunderstorms dropped hail up to 1.75 inches in diameter in a 4-mile wide swath from 2 miles west of Sun Prairie to around 4 miles south-southwest of Columbus.

Thunderstorm Wind in RACINE, WISCONSIN
From 22-MAY-11 18:45:00 to 22-MAY-11 18:50:00 (CST-6)
Location: BURLINGTON
Magnitude: 70.00 EG
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Newspaper

Severe thunderstorms produced damaging wind gusts estimated at 80 mph. Many power lines and trees were taken down by the strong winds, and several homes and cars were damaged.

Thunderstorm Wind in RACINE, WISCONSIN
From 22-MAY-11 18:54:00 to 22-MAY-11 18:54:00 (CST-6)
Location: UNION GROVE
Magnitude: 52.00 MG
Reported by: Mesonet

Hail in JEFFERSON, WISCONSIN
From 22-MAY-11 16:30:00 to 22-MAY-11 16:35:00 (CST-6)
Location: LAKE MILLS
Magnitude: 1.00 
Reported by: Amateur Radio

Ham radio operators reported severe thunderstorms dropped hail up to 1.00 inch in diameter in a 3-mile wide swath from 3 miles southwest of Lake Mills to 1 mile northeast of Lake Mills.

Tornado in GREEN LAKE, WISCONSIN
From 22-MAY-11 18:33:00 to 22-MAY-11 18:34:00 (CST-6)
Location: DALTON
Tornado F-scale: EF0
Property damage: 1.00K
Reported by: Emergency Manager

An EF0 tornado spun up about 2 miles south-southwest of Kingston about 900 ft southeast of the intersection of County Road H and State Highway 44 and traveled northeast approximately 1/3 mile before dissipating just south of State Highway 44. The tornado damaged a door on a shed, broke tree branches, and damaged a greenhouse. The EF-rating was based on DI 27(TH) DOD 2 with winds of 65 mph. The starting location was 43.658216/-89.185059 and the ending location was 43.661958/-89.179995. Average path width was about 15 yards.

Hail in WALWORTH, WISCONSIN
From 22-MAY-11 17:01:00 to 22-MAY-11 17:01:00 (CST-6)
Location: WHITEWATER
Magnitude: 1.25 
Reported by: Amateur Radio

Hail in WASHINGTON, WISCONSIN
From 22-MAY-11 17:35:00 to 22-MAY-11 17:35:00 (CST-6)
Location: JACKSON
Magnitude: 1.00 
Reported by: Public

Hail in WALWORTH, WISCONSIN
From 22-MAY-11 17:05:00 to 22-MAY-11 17:10:00 (CST-6)
Location: RICHMOND
Magnitude: 1.75 
Reported by: Amateur Radio

Hail in OZAUKEE, WISCONSIN
From 22-MAY-11 17:37:00 to 22-MAY-11 17:37:00 (CST-6)
Location: WAUBEKA
Magnitude: 1.00 
Reported by: Public

Hail in WAUKESHA, WISCONSIN
From 22-MAY-11 17:18:00 to 22-MAY-11 17:30:00 (CST-6)
Location: EAGLE
Magnitude: 1.75 
Reported by: Fire Department/Rescue

A severe thunderstorm produced hail up to 1.75 inches in diameter in a 4-mile wide swath from the southwest corner of Waukesha County northeast to North Prairie.

Thunderstorm Wind in WASHINGTON, WISCONSIN
From 22-MAY-11 17:12:00 to 22-MAY-11 17:15:00 (CST-6)
Location: HARTFORD
Magnitude: 56.00 EG
Property damage: 10.00K
Reported by: Public

Severe thunderstorms affected locations along a Hartford to Allenton line with damaging winds. The severe wind gusts downed trees that damaged a car and a house.

Thunderstorm Wind in DODGE, WISCONSIN
From 22-MAY-11 17:05:00 to 22-MAY-11 17:05:00 (CST-6)
Location: HUSTISFORD
Magnitude: 56.00 EG
Property damage: 0.50K
Reported by: Public

A second round of severe thunderstorms affected Hustisford with damaging winds. This round downed trees that damaged a fence and did $500 worth of damage to a house.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 22-MAY-11 17:10:00 to 22-MAY-11 17:10:00 (CST-6)
Location: WHITEWATER
Magnitude: 52.00 EG
Property damage: 5.00K
Reported by: Trained Spotter

A trained spotter reported severe thunderstorm wind gusts that downed trees and tree limbs in Whitewater.

Thunderstorm Wind in SHEBOYGAN, WISCONSIN
From 22-MAY-11 17:39:00 to 22-MAY-11 17:45:00 (CST-6)
Location: RANDOM LAKE
Magnitude: 52.00 MG
Reported by: Trained Spotter

A trained spotter reported severe thunderstorm wind gusts that downed trees and tree limbs along a line from Random Lake to a mile west of Cedar Grove.

Thunderstorm Wind in KENOSHA, WISCONSIN
From 22-MAY-11 18:48:00 to 22-MAY-11 18:50:00 (CST-6)
Location: SILVER LAKE
Magnitude: 70.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Newspaper

Severe thunderstorms produced damaging wind gusts estimated at 80 mph (70 knots). Many power lines and trees were taken down by the strong winds, and several homes and cars were damaged, including a home that had the roof taken off by the severe wind gusts.

Thunderstorm Wind in MILWAUKEE, WISCONSIN
From 22-MAY-11 19:02:00 to 22-MAY-11 19:07:00 (CST-6)
Location: (MKE)MITCHELL APT MI
Magnitude: 53.00 MG
Reported by: ASOS

A severe thunderstorm produced wind gusts measured up to 61 mph. The winds blew off a portion of the roof of a Day Inn at 13th Street and College Avenue.

Hail in JEFFERSON, WISCONSIN
From 22-MAY-11 17:27:00 to 22-MAY-11 17:27:00 (CST-6)
Location: OAK HILL
Magnitude: 1.25 
Reported by: Official NWS Observations

Thunderstorm Wind in DODGE, WISCONSIN
From 22-MAY-11 16:40:00 to 22-MAY-11 16:40:00 (CST-6)
Location: HUSTISFORD
Magnitude: 60.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Numerous trees and power lines were reported blown down by damaging thunderstorm wind gusts in the Hustisford area. A tree fell on a home damaging the roof. A tree fell on an occupied car, and the driver injured his shoulder (indirectly-related) exiting the car. Total damage in the area amounted to $10,000.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 22-MAY-11 18:30:00 to 22-MAY-11 18:30:00 (CST-6)
Location: ELKHORN
Magnitude: 52.00 EG
Property damage: 10.00K
Reported by: Emergency Manager

A severe thunderstorm produced wind gusts that downed power lines, trees and tree limbs just south of Elkhorn. The downed trees and limbs damaged a few homes as well as a fence.

Hail in SAUK, WISCONSIN
From 22-MAY-11 17:18:00 to 22-MAY-11 17:18:00 (CST-6)
Location: REEDSBURG
Magnitude: 0.75 
Reported by: Public

Tornado in GREEN LAKE, WISCONSIN
From 22-MAY-11 18:47:00 to 22-MAY-11 18:55:00 (CST-6)
Location: MARKESAN
Tornado F-scale: EF0
Property damage: 5.00K
Reported by: Emergency Manager

An EF0 tornado spun up about 0.3 miles northwest of downtown Markesan just west of State Highway 44 (Margaret Street) about 1/2 mile south of the intersection with County Road H and traveled east-northeast slightly over 4 miles before dissipating near Utley, about 1/4 mile west-northwest of the intersection of Utley Road and County Highway Q. The tornado broke tree branches, with some of them snapping a couple power lines. The EF-rating was based on DI 27(TH) DOD 2 with winds of 75 mph. The starting location was 43.715256/-88.992648 and the ending location was 43.728902/-88.910465. The average path width was about 30 yards.

Hail in MARQUETTE, WISCONSIN
From 22-MAY-11 14:00:00 to 22-MAY-11 14:00:00 (CST-6)
Location: WESTFIELD
Magnitude: 2.00 
Reported by: Trained Spotter

A trained spotter reported leaves stripped from trees in Westfield by large hail.