A frontal boundary draped across central and southern Wisconsin was the focus for the development of thunderstorms during the day on July 18th. An upper-level wave moving out of the Plains towards the western Great Lakes provided extra dynamic lift and shear to produce severe thunderstorms with large hail up to 2 inches in diameter and damaging wind gusts up to 71 mph during the late afternoon and evening hours.  There were many reports of uprooted trees and broken large tree branches and scattered reports of power outages once tree debris fell on power-lines.

Hail in ROCK, WISCONSIN
From 18-JUL-12 16:43:00 to 18-JUL-12 16:43:00 (CST-6)
Location: EVANSVILLE
Magnitude: 1.00 
Reported by: Law Enforcement

Hail in ROCK, WISCONSIN
From 18-JUL-12 16:50:00 to 18-JUL-12 16:50:00 (CST-6)
Location: ORFORDVILLE
Magnitude: 2.00 
Property damage: 6.00K
Reported by: Trained Spotter

Hail up to 2 inches in diameter damaged the roof on a farm house 4 miles north of the town of Orfordville.

Thunderstorm Wind in ROCK, WISCONSIN
From 18-JUL-12 16:50:00 to 18-JUL-12 16:50:00 (CST-6)
Location: ORFORDVILLE
Magnitude: 50.00 EG
Reported by: Trained Spotter

A trained spotter reported many large tree branches blown down by damaging thunderstorm winds estimated to be 58 mph (50 knots).

Thunderstorm Wind in SAUK, WISCONSIN
From 18-JUL-12 16:41:00 to 18-JUL-12 16:41:00 (CST-6)
Location: LONE ROCK AIRPORT
Magnitude: 52.00 MG
Reported by: ASOS

Thunderstorm Wind in IOWA, WISCONSIN
From 18-JUL-12 16:42:00 to 18-JUL-12 16:42:00 (CST-6)
Location: HIGHLAND
Magnitude: 56.00 EG
Reported by: Law Enforcement

Law enforcement officials reported a hay wagon was blown over by severe thunderstorm wind gusts estimated at 65 mph (56 knots).

Thunderstorm Wind in IOWA, WISCONSIN
From 18-JUL-12 16:51:00 to 18-JUL-12 16:51:00 (CST-6)
Location: DODGEVILLE
Magnitude: 56.00 EG
Reported by: Law Enforcement

Law enforcement officials reported trees and power lines blown down by severe thunderstorm wind gusts estimated at 65 mph (56 knots).

Thunderstorm Wind in ROCK, WISCONSIN
From 18-JUL-12 16:54:00 to 18-JUL-12 16:54:00 (CST-6)
Location: ORFORDVILLE
Magnitude: 56.00 EG
Reported by: Trained Spotter

A trained spotter reported trees and power lines blown down by severe thunderstorm wind gusts estimated at 65 mph (56 knots).

Thunderstorm Wind in SAUK, WISCONSIN
From 18-JUL-12 16:50:00 to 18-JUL-12 17:15:00 (CST-6)
Location: SAUK CITY
Magnitude: 70.00 EG
Reported by: Law Enforcement

Law enforcement officials reported building damage in Sauk City caused by severe thunderstorm wind gusts estimated at 80 mph (70 knots).

Thunderstorm Wind in DANE, WISCONSIN
From 18-JUL-12 17:35:00 to 18-JUL-12 17:35:00 (CST-6)
Location: MT HOREB
Magnitude: 62.00 MG
Reported by: Trained Spotter

A trained spotter measured a severe thunderstorm wind gust of 71 mph (62 knots).

Thunderstorm Wind in GREEN, WISCONSIN
From 18-JUL-12 18:12:00 to 18-JUL-12 18:15:00 (CST-6)
Location: MONROE
Magnitude: 53.00 MG
Reported by: Amateur Radio

A ham radio operator measured a severe thunderstorm wind gust of 61 mph (53 knots).

Thunderstorm Wind in RACINE, WISCONSIN
From 18-JUL-12 19:11:00 to 18-JUL-12 19:11:00 (CST-6)
Location: DOWNTOWN RACINE
Magnitude: 56.00 EG
Reported by: Amateur Radio

A ham radio operator reported a severe thunderstorm wind gust estimated at 65 mph (56 knots).

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 18-JUL-12 18:25:00 to 18-JUL-12 18:25:00 (CST-6)
Location: WATERTOWN
Magnitude: 52.00 EG
Reported by: Trained Spotter

A trained spotter reported a severe thunderstorm wind gust estimated at 60 mph (52 knots).

Lightning in ROCK, WISCONSIN
From 18-JUL-12 18:20:00 to 18-JUL-12 18:20:00 (CST-6)
Location: ORFORDVILLE
Property damage: 3.00K
Reported by: Law Enforcement

Law enforcement officials reported a telephone pole caught fire after being struck by lightning northwest of Orfordville.