A weak semi-stationary boundary remained draped across Iowa in the overnight hours of the 20th into the 21st, which acted as a focus for initial storm development.  Storms early in the evening moved off to the southeast and was relatively quiet until the low level jet kicked in.  The overall convective environment was modest with MUCAPE values around 1000-2000 J/kg and unsupportive effective shear and best supported widespread back building convection.  While there were not many heavy rainfall reports, a report of 3.50 inches was made on the morning of the 21st.  Radar estimates put many areas in excess of 5 inches, causing local river and flash flooding.  Through the day and next evening, scattered storms and low level jet induced convection added another local 1 to 2 inches and exacerbated some localized flash flooding issues.

Flash Flood in BREMER, IOWA
From 22-JUL-17 00:35:00 to 22-JUL-17 12:35:00 (CST-6)
Location: SUMNER
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported several houses with water flooding into basement along with numerous roads covered with water up to 1 foot in places.  At least one person reported as being evacuated from their home.

Flash Flood in BREMER, IOWA
From 22-JUL-17 04:41:00 to 22-JUL-17 12:35:00 (CST-6)
Location: SCHWERIN FLD ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Iowa DOT reports Highway 93 between county road V48 and county road V68 is blocked due to flooding.

Flash Flood in BREMER, IOWA
From 22-JUL-17 03:00:00 to 22-JUL-17 12:35:00 (CST-6)
Location: SUMNER
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported up to a dozen evacuations from high water around the Sumner area.  Multiple road closures as well.

Heavy Rain in BREMER, IOWA
From 20-JUL-17 20:30:00 to 21-JUL-17 02:30:00 (CST-6)
Location: SUMNER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported heavy rainfall of 3.50 inches form morning rainfall and also reported road closures in town.

Flash Flood in BREMER, IOWA
From 21-JUL-17 09:40:00 to 21-JUL-17 14:50:00 (CST-6)
Location: SCHWERIN FLD ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported water over the road in the 2900 block of 150th st.  This is a delayed report.

Flash Flood in BREMER, IOWA
From 21-JUL-17 11:00:00 to 21-JUL-17 14:50:00 (CST-6)
Location: BUCK CREEK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported road washed out at 180th st and Y ave.

Flash Flood in BREMER, IOWA
From 22-JUL-17 06:36:00 to 22-JUL-17 12:35:00 (CST-6)
Location: BREMER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported water over portions of Highway 63 west of Tripoli.  Depth was unknown, but noted water covering several locations of the highway.

Flash Flood in BREMER, IOWA
From 22-JUL-17 04:42:00 to 22-JUL-17 12:35:00 (CST-6)
Location: SUMNER
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported total evacuations in Sumner now.  Numerous roads continue to be underwater.  Electrical power in Sumner has been interrupted as well.

Flash Flood in BREMER, IOWA
From 22-JUL-17 06:36:00 to 22-JUL-17 12:35:00 (CST-6)
Location: BUCK CREEK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported secondary roads just east-northeast of Readlyn covered with water and Highway 3 close to being inundated.