A slow moving low pressure area within a very moist airmass resulted in rounds of heavy rainfall and flash flooding. More specifically, a prolonged period of heavy rainfall over northern Jefferson County, far southern Dodge County, and northeast Dane County resulted in 4 to 8 inches of rain and flash flooding. The cities of Watertown and Waterloo experienced the worst of the flooding.

Hail in FOND DU LAC, WISCONSIN
From 16-AUG-18 13:30:00 to 16-AUG-18 13:30:00 (CST-6)
Location: LADOGA
Magnitude: 1.00 
Reported by: Public

Thunderstorm Wind in FOND DU LAC, WISCONSIN
From 16-AUG-18 13:40:00 to 16-AUG-18 13:40:00 (CST-6)
Location: BRANDON
Magnitude: 50.00 EG
Property damage: 2.00K
Reported by: NWS Employee

Several large trees down.

Flood in JEFFERSON, WISCONSIN
From 17-AUG-18 11:15:00 to 17-AUG-18 23:59:00 (CST-6)
Location: WATERLOO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Flooded roads, yards, fields, and basements continued the remainder of the day with some improvement after 5 to 8 inches of rain.  The cities of Watertown and Waterloo were most impacted by the flood waters. The Rock River in Watertown briefly reached minor flood stage from 11:10 AM CST to 12:00 PM CST. Lowland areas and parks near the Rock River were flooded throughout northern Jefferson County.

Flash Flood in DANE, WISCONSIN
From 17-AUG-18 06:15:00 to 17-AUG-18 11:15:00 (CST-6)
Location: MARSHALL
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 1.00K
Reported by: Law Enforcement

Flash flooding of some streets in Marshall. Schlimgen Rd. near the Deansville State Wildlife Area was closed due to flooding.

Flash Flood in DODGE, WISCONSIN
From 17-AUG-18 06:15:00 to 17-AUG-18 11:15:00 (CST-6)
Location: PORTLAND
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 1.00K
Reported by: Law Enforcement

Approximately 100 911 calls related to flash flooding in Watertown. Numerous streets in Watertown flooded and closed. Some neighborhoods completely flooded with streets, yards, and driveways filled with water. Basement flooding common. Three vehicle water rescues involving 4 citizens performed by the fire department. Railroad tracks compromised by soil erosion underneath the tracks.  The flooding caused a sanitary sewer overflow/bypass around 10 AM. Lowland flooding in rural areas of far southern Dodge County.

Flash Flood in ROCK, WISCONSIN
From 16-AUG-18 22:00:00 to 17-AUG-18 01:15:00 (CST-6)
Location: MILTON JCT
Flood cause: Heavy Rain
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flash flooding of streets in Milton. 4 vehicles stalled in deep water on Arthur Dr. near St. Mary's St. A portion of Madison Rd. was closed due to high water.

Flash Flood in JEFFERSON, WISCONSIN
From 17-AUG-18 06:15:00 to 17-AUG-18 11:15:00 (CST-6)
Location: WATERLOO
Flood cause: Heavy Rain
Property damage: 943.00K
Crop damage: 1.00K
Reported by: Law Enforcement

Approximately 100 911 calls related to flash flooding in Watertown. Numerous streets in Watertown flooded and closed. Some neighborhoods completely flooded with streets, yards, and driveways filled with water. Basement flooding common. A portion of Jefferson Rd. washed out at the bridge where a creek flows into the nearby Rock River. Other road damage or washouts as well. Three vehicle water rescues involving 4 citizens performed by the fire department. A section of track ballast was washed away compromising the railroad ties and tracks. The flooding caused a sanitary sewer overflow/bypass around 10 AM.  Additional street flooding and basement flooding in Waterloo, Ixonia, and northern Jefferson County with some city streets and county roads closed and damaged. Overall, 93 homes sustained affected damage and 66 homes with minor damage. 5 businesses also sustained minor damage.

Heavy Rain in MILWAUKEE, WISCONSIN
From 17-AUG-18 05:30:00 to 17-AUG-18 11:00:00 (CST-6)
Location: GLENDALE
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rainfall in a construction zone resulted in a flooded I-43 at Green Tree Rd. on two separate occasions during the morning hours.  Both lanes of I-43 were closed in both instances. Before the first closing, 6 vehicles were stranded in deep water and four occupants of the vehicles had to be rescued by the fire department.

Flood in DODGE, WISCONSIN
From 17-AUG-18 11:15:00 to 17-AUG-18 23:59:00 (CST-6)
Location: PORTLAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flooded roads, yards, fields, and basements continued the remainder of the day with some improvement after 5 to 8 inches of rain.  The city of Watertown was most impacted by the flood waters.