Thunderstorms that developed in warm, moist and unstable air ahead of an approaching cold front produced torrential rain that resulted in significant flash flooding, especially in the Oshkosh (Winnebago Co.) area.  Heavy rainfall caused street and other nuisance flooding in Waushara Co., Brown Co., Door Co. and Kewaunee Co.  The State of Wisconsin suffered over a half billion dollars in damage from this flooding event.
The storms also produced some large hail and wind damage.

Thunderstorm Wind in WINNEBAGO, WISCONSIN
From 12-JUN-08 15:42:00 to 12-JUN-08 15:42:00 (CST-6)
Location: OSHKOSH
Magnitude: 52.00 MG
Reported by: Trained Spotter

Hail in PORTAGE, WISCONSIN
From 12-JUN-08 15:57:00 to 12-JUN-08 15:57:00 (CST-6)
Location: CUSTER
Magnitude: 0.75 
Reported by: Law Enforcement

Flash Flood in MANITOWOC, WISCONSIN
From 12-JUN-08 20:00:00 to 12-JUN-08 23:00:00 (CST-6)
Location: MANITOWOC
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 20.00M
Reported by: Other Federal Agency

Torrential rain, including 5.10 inches in Valders, caused the Manitowoc River to rise three feet in four hours.  Resultant flooding washed out part of State Highway 57 near Kiel and created a large pothole on Clarks Mills Road.

Hail in LANGLADE, WISCONSIN
From 12-JUN-08 16:30:00 to 12-JUN-08 16:30:00 (CST-6)
Location: FREEMAN
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LANGLADE, WISCONSIN
From 12-JUN-08 16:33:00 to 12-JUN-08 16:33:00 (CST-6)
Location: PICKEREL
Magnitude: 0.75 
Reported by: Amateur Radio

Penny size hail was reported at the intersection of Highway 55 and County Road A.

Thunderstorm Wind in CALUMET, WISCONSIN
From 12-JUN-08 16:15:00 to 12-JUN-08 16:15:00 (CST-6)
Location: HIGH CLIFF
Magnitude: 50.00 EG
Reported by: Law Enforcement

Thunderstorm winds downed trees on State Park Road, south of Highway 10.

Thunderstorm Wind in BROWN, WISCONSIN
From 12-JUN-08 18:00:00 to 12-JUN-08 18:00:00 (CST-6)
Location: DE PERE NICOLET ARPT
Magnitude: 56.00 EG
Reported by: Amateur Radio

Large road signs were blown off their anchoring poles by thunderstorms winds on Highway 172 at the Fox River.

Thunderstorm Wind in BROWN, WISCONSIN
From 12-JUN-08 18:09:00 to 12-JUN-08 18:09:00 (CST-6)
Location: DENMARK
Magnitude: 52.00 EG
Reported by: Amateur Radio

Thunderstorm winds downed 8 to 10 inch diameter tree limbs.

Thunderstorm Wind in MANITOWOC, WISCONSIN
From 12-JUN-08 17:50:00 to 12-JUN-08 17:50:00 (CST-6)
Location: ROSECRANS
Magnitude: 55.00 EG
Reported by: Public

Strong thunderstorm winds downed and twisted trees near Maribel.

Flash Flood in WINNEBAGO, WISCONSIN
From 12-JUN-08 17:21:00 to 12-JUN-08 23:13:00 (CST-6)
Location: OSHKOSH
Flood cause: Heavy Rain
Property damage: 18.60M
Crop damage: 4.50M
Reported by: Emergency Manager

Heavy rainfall, totaling 5.41 inches for the day, over already saturated ground caused widespread flash flooding in the Oshkosh area.  Sewage backed up into many basements and the foundations of some homes on the south side of the city crumbled, making them uninhabitable.  The flooding destroyed 20 homes, caused major damage to 150, and caused minor damage to over 400 others.  Several schools sustained damage, including Lourdes High School and the attached St. John Neumann Middle School, which had extensive water and sewage damage.  Water built up in the parking lot and caved in windows on the school's lower level.  Flood waters rose over five feet, destroying classrooms, athletic equipment, carpets and computers.  Damage to the schools was well over $1 million.  The University of Wisconsin-Oshkosh campus also sustained some water damage.  High water made 50 to 75 percent of the streets impassible, including parts of U.S. Highways 41 and 45.  It also washed out a railroad bridge causing a train to derail and spill diesel fuel into the floodwaters.

Flash Flood in CALUMET, WISCONSIN
From 12-JUN-08 18:00:00 to 12-JUN-08 23:45:00 (CST-6)
Location: ST ANNA
Flood cause: Heavy Rain
Property damage: 480.00K
Crop damage: 5.00M
Reported by: Emergency Manager

Torrential rain flooded roads and washed out a 10 foot section of railroad ties near Highway BB south of St. John.  Numerous streets and basements were flooded and the St. Ana Fire Department needed to be sand bagged to avoid flooding.  The flooding caused major damage to 1 home and minor damage to 60 others.