A very unstable airmass was in place over Iowa ahead of an approaching cold front and short wave.  The cold front itself was over South Dakota, and set off a line of severe thunderstorms in front of it.  Over central into south central Iowa, extending into the northeast counties, strong to severe thunderstorms broke out shortly after peak heating.  Daytime highs reached the mid 80s to mid 90s across the state with dew points in the upper 70s to low 80s.  Precipitable water values increased to between 1.8 and 2.3 inches across the central counties.  CAPE increased to 4000-5000 J/kg with lifted indices falling to the -8 to -11 C range.  The atmosphere was moderately sheared with 35 to 50 kts of shear available.  The LCL was a relatively low 500 to 1000 meters.  Downdraft CAPE was 1000 to 1700 J/kg, with 700-1000 J/kg of CAPE in the -10 to -30 C layer of the atmosphere.  The freezing level was between 15,000 and 15,500 feet.  Thunderstorms fired in central Iowa and became severe quite quickly.  One storm produced two tornadoes in the Indianola area of Warren County.  One hit to the west of Indianola.  Several houses were damaged near Euclid St and Y Street.  Houses and barns were damaged at the intersection of R63 and Hover Street.  The total number of homes damages was 22 with 5 sustaining major damage.  The major damage included wall damage to homes, collapsed walls on garages, and uplift of decks and roofs.  The wind speed was around 100 MPH.  The second one touched down just east of the main part of town and caused building damage.  Damage included inward and outward collapse of overhead doors to a garage and metal outbuildings.  It was on the ground for less than one half mile and produced winds around 90 MPH.  The storms went on to produce wind gusts in excess of 60 MPH in Marion and Jasper Counties.  Damage was reported to farmsteads, as well as to trees and power lines.  The storms were heavy rain producers.  Heavy rain fell, with 2 to 3 inches of rain falling in about an hour over Warren County.  Reports of 1 to 2 feet of flowing water over Highway 92 were received.  Water stranded people in a trailer court west of Highway 65/60 south of Indianola.  Attention turned to storms forming closer to the cold front.  Strong to severe thunderstorms moved into northwest Iowa and produced severe weather after midnight in north central Iowa.  Wind damage was reported in the Mason City area shortly after midnight.  Heavy rainfall continued over north central Iowa.  Parts of the area around Waterloo and Dewar received between 4 and 9 inches of rain over the previous 48 hours, 2 to 5 of which fell just prior to the flash flooding.  The flooding closed roads in the area.  Lightning struck a house north of Des Moines during the evening.  Damage was limited, but circuits were blown out.

Tornado in WARREN, IOWA
From 23-JUL-10 19:03:00 to 23-JUL-10 19:11:00 (CST-6)
Location: SPRING HILL
Tornado F-scale: EF1
Property damage: 750.00K
Crop damage: 10.00K
Reported by: NWS Storm Survey

Tornado west to west northwest of Indianola.  Multiple reports with barns and houses damaged.

Thunderstorm Wind in MARION, IOWA
From 23-JUL-10 20:02:00 to 23-JUL-10 20:02:00 (CST-6)
Location: PLEASANTVILLE
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Measured wind gust at the intersection of Lisbon and Highway S45.

Thunderstorm Wind in MARION, IOWA
From 23-JUL-10 19:54:00 to 23-JUL-10 19:54:00 (CST-6)
Location: PLEASANTVILLE
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flash Flood in BLACK HAWK, IOWA
From 24-JUL-10 03:30:00 to 24-JUL-10 06:30:00 (CST-6)
Location: DEWAR
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Two roads were closed due to flooding.

Thunderstorm Wind in CERRO GORDO, IOWA
From 24-JUL-10 00:30:00 to 24-JUL-10 00:30:00 (CST-6)
Location: MASON CITY
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees were down on the zero block of 10th Street NW.

Thunderstorm Wind in CERRO GORDO, IOWA
From 24-JUL-10 00:30:00 to 24-JUL-10 00:30:00 (CST-6)
Location: MASON CITY
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power line was down on the 300 block of Kentucky Ave.

Thunderstorm Wind in CERRO GORDO, IOWA
From 24-JUL-10 01:00:00 to 24-JUL-10 01:00:00 (CST-6)
Location: MASON CITY
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Tree down on the 1000 block of 9th Street NE.  Sixty MPH wind gust estimated by storm spotter.

Tornado in WARREN, IOWA
From 23-JUL-10 19:12:00 to 23-JUL-10 19:13:00 (CST-6)
Location: BEECH
Tornado F-scale: EF1
Property damage: 250.00K
Crop damage: 5.00K
Reported by: NWS Storm Survey

Several houses damaged.

Lightning in POLK, IOWA
From 23-JUL-10 21:25:00 to 23-JUL-10 21:25:00 (CST-6)
Location: LOVINGTON
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lightning hit a house and caused some blown circuits.

Flash Flood in WARREN, IOWA
From 23-JUL-10 20:20:00 to 23-JUL-10 22:55:00 (CST-6)
Location: INDIANOLA
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement and amateur radio reported at least 18 inches of water flowing through a trailer park just west of Highway 65/69 with people stranded.

Thunderstorm Wind in JASPER, IOWA
From 23-JUL-10 20:10:00 to 23-JUL-10 20:10:00 (CST-6)
Location: PRAIRIE CITY
Magnitude: 65.00 EG
Property damage: 35.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Report of wind damage to a farm with several trees and power poles down, and an out building damaged.

Flash Flood in WARREN, IOWA
From 23-JUL-10 21:16:00 to 23-JUL-10 22:55:00 (CST-6)
Location: ACKWORTH
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

One to two feet of flowing water over Highway S23 north of Highway 92.

Flash Flood in WARREN, IOWA
From 23-JUL-10 21:16:00 to 23-JUL-10 22:55:00 (CST-6)
Location: SANDYVILLE
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

One to two feet of water flowing over Highway 92 at the South River.