An unstable airmass was in place across Iowa with afternoon highs reaching well into the 80s, and dewpoint readings in the low to mid 70s.  CAPE rose to 2000 to 3000 J/kg.  Downdraft CAPE was around 900 to 1000 J/kg with CAPE in the -10 to -30 C layer of the atmosphere in the 600 to 900 J/kg range.  Precipitable water increased to around 1.75 inches.  The freezing level was quite high, around 15,000 feet.  Fairly strong shear was present with 40 to 50 kts of effective shear by late afternoon.  A line of thunderstorms formed ahead of the cold front by late afternoon and moved east across the state through the evening hours.  Hail with the storms was generally quite small.  One inch diameter hail fell in Crawford County in Dow City.  The primary severe events from this system were the high winds that occurred as the MCS progressed across the state.  Several locations reported gusts of 60 MPH or higher.  An 80 MPH was reported in Guthrie County at Yale and Bayard.  A 71 MPH wind gust occurred in Marion County.  Heavy rainfall was also of significance with flash flooding in Crawford County.  This caused by a dam failure, which flooded Highway 39.  Three inches of rain fell in 50 minutes in Dallas County.  There were numerous reports of around 2 inches of rain falling in Boone and Polk Counties.  Water ponding and lowland flooding was common.  One person was struck by lightning at the Denison Airport.  The person received minor injuries. Funnel clouds were sighted in both Crawford and Boone Counties. The heavy rain also led to river flooding along the Raccoon River at Fleur Drive in Des Moines. The river was in flood for around 1 day and crested at 2 feet above flood stage. Additional heavy rainfall reports can be found in the 31 August 2014 event.

Heavy Rain in POLK, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: POLK CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.24 inches.

Heavy Rain in STORY, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: NEVADA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.26 inches.

Heavy Rain in STORY, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: AMES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.22 inches.

Flood in POLK, IOWA
From 01-SEP-14 12:00:00 to 02-SEP-14 12:15:00 (CST-6)
Location: DES MOINES
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Heavy Rain in STORY, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: AMES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.23 inches.

Heavy Rain in HARDIN, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: ELDORA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Rainfall of 2.10 inches reported.

Heavy Rain in POLK, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: DES MOINES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Rainfall of 1.85 inches reported.

Heavy Rain in DALLAS, IOWA
From 01-SEP-14 07:00:00 to 01-SEP-14 07:00:00 (CST-6)
Location: DALLAS CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Rainfall of 2.00 inches reported.

Heavy Rain in CALHOUN, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: ROCKWELL CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 2.13 inches.

Heavy Rain in STORY, IOWA
From 01-SEP-14 07:00:00 to 01-SEP-14 07:00:00 (CST-6)
Location: NEVADA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Rainfall of 2.26 inches reported.

Heavy Rain in MARSHALL, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: MARSHALLTOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 2.31 inches.

Heavy Rain in POLK, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: DES MOINES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Rainfall of 2.19 inches at the Des Moines International Airport.

Heavy Rain in STORY, IOWA
From 01-SEP-14 07:00:00 to 01-SEP-14 07:00:00 (CST-6)
Location: SLATER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Rainfall of 2.50 inches reported.

Heavy Rain in MARSHALL, IOWA
From 01-SEP-14 07:00:00 to 01-SEP-14 07:00:00 (CST-6)
Location: MARSHALLTOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Rainfall of 2.40 inches reported.

Heavy Rain in STORY, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: SHIPLEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 2.43 inches.

Heavy Rain in STORY, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: AMES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Rainfall of 2.31 inches.

Heavy Rain in BOONE, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: MADRID
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.36 inches.

Heavy Rain in CRAWFORD, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: SCHLESWIG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 3.06 inches.

Heavy Rain in DALLAS, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: DALLAS CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.62 inches.

Heavy Rain in GUTHRIE, IOWA
From 01-SEP-14 06:00:00 to 01-SEP-14 06:00:00 (CST-6)
Location: BAGLEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Rainfall of 2.15 inches.