A broken line of strong to severe thunderstorms formed along and ahead of a cold front...with lift further enhanced by a short wave passing through the region. Southern Wisconsin was in a strongly unstable air mass ahead of the front, with temperatures in the lower 90s and dew points in the upper 70s to around 80 degrees F. Mixed Layer CAPE values reached 3000 to 4000 J/Kg, and when combined with deep layer shear of 30 to 40 knots, set up conditions favorable for organized storm modes, including supercells and bowing segments. The resulting severe thunderstorms produced large hail and damaging wind gusts across portions of Rock County and the southern-most counties of Southeast Wisconsin.  Up to 11,600 We Energies customers were without power in Racine and Kenosha Counties alone at the height of the storms.

Hail in ROCK, WISCONSIN
From 02-AUG-11 16:05:00 to 02-AUG-11 16:07:00 (CST-6)
Location: DOWNTOWN JANESVILLE
Magnitude: 2.25 
Reported by: Public

The father of a trained spotter reported a severe thunderstorm that produced 2.25 inch hail as it moved east-southeast along State Highway 11 from downtown Janesville.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 02-AUG-11 16:30:00 to 02-AUG-11 16:30:00 (CST-6)
Location: DELAVAN ARPT
Magnitude: 56.00 EG
Reported by: Law Enforcement

Police officers reported trees blown down along the northeast side of Delavan Lake by thunderstorm wind gusts estimated at 65 mph (56 knots). One dozen trees were blown over on the Lake Lawn Resort property in Delavan in Walworth County, which saw almost 40 trees downed by a storm earlier in the summer.

Thunderstorm Wind in KENOSHA, WISCONSIN
From 02-AUG-11 17:00:00 to 02-AUG-11 17:00:00 (CST-6)
Location: TWIN LAKES
Magnitude: 50.00 EG
Reported by: Law Enforcement

Police officers reported trees, tree limbs and power lines blown down in Twin Lakes in southwest Kenosha County by thunderstorm wind gusts estimated at 58 mph (50 knots).

Thunderstorm Wind in KENOSHA, WISCONSIN
From 02-AUG-11 17:18:00 to 02-AUG-11 17:18:00 (CST-6)
Location: PLEASANT PRAIRIE
Magnitude: 55.00 EG
Reported by: Emergency Manager

The Kenosha County Emergency Manager reported trees and tree limbs blown down near Pleasant Prairie in far southeast Kenosha County by thunderstorm wind gusts estimated at 63 mph (55 knots). A semi-trailer was also blown over by the damaging wind gusts.

Thunderstorm Wind in RACINE, WISCONSIN
From 02-AUG-11 16:58:00 to 02-AUG-11 16:58:00 (CST-6)
Location: DOWNTOWN RACINE
Magnitude: 56.00 EG
Reported by: Amateur Radio

An amateur radio operator reported trees, tree limbs and power lines blown down west-northwest of downtown Racine by thunderstorm wind gusts estimated at 65 mph (56 knots). The downed trees and power lines blocked the roads near the intersection of Spring Street and Emmertsen Road.

Funnel Cloud in KENOSHA, WISCONSIN
From 02-AUG-11 17:10:00 to 02-AUG-11 17:10:00 (CST-6)
Location: PLEASANT PRAIRIE
Reported by: Trained Spotter

Thunderstorm Wind in WALWORTH, WISCONSIN
From 02-AUG-11 16:50:00 to 02-AUG-11 16:50:00 (CST-6)
Location: WILLIAMS BAY
Magnitude: 56.00 EG
Reported by: Newspaper

Powerful thunderstorm winds toppled about a dozen trees in the Kishwauketoe Nature Conservancy of Williams Bay in Walworth County.  It was estimated that 1000 volunteer hours and $6000 would be needed to clean up the tree debris over a span of about 6 weeks.  This clean-up cost is indirectly related to the thunderstorm winds.  Several trees were knocked over by the winds within the Village of Williams Bay, which resulted in snapped power-lines.  Monetary damage amounts from the Village were not available.