A strong warm front was in place across central Nebraska through northern Missouri.  The front aloft bisected Iowa from northwest to southeast.  A 35 kt low level jet was in place with strong moisture transport into the state.  Precipitable water values were in the 1.2 to 1.4 inch range.  The atmosphere was fairly strongly sheared with 35 to 50 kts of available shear.  Elevated CAPE was in the 500 to 1000 J/kg range.  Downdraft CAPE was relatively low, less than 500 J/kg.  The freezing level was around 13,500 feet with CAPE in the -10 to -30 C layer of the atmosphere around 200 J/kg.  Thunderstorms fired along the 850 mb warm front from northwest, through central, into southeast Iowa.  Many of the storms produced small hail with a few becoming severe.  Nickel to quarter size hail fell in the Audubon area.  The predominant threat was the heavy rainfall.  Intense storms dropped 4 to 8 inches of rain over parts of Jasper and Poweshiek Counties.  The highest measured observation was 6.74 inches in Brooklyn in Poweshiek County.  U.S. Highway 6 was closed in the Kellogg and Oakland Acres areas.  Cars were trapped by the high water in the Oakland Acres area as well.  Several bridges were washed out in the area.  As the water rose, the water treatment plant was flooded in the town of Kellogg.  Thunderstorms continued to expand over north central Iowa.  Flash flooding and flooded streets were reported in Hardin, Franklin, Marshall, and Grundy Counties.  As the thunderstorm complex weakened, a wake low formed on the west side of the complex.  Gusty easterly winds developed with high winds in a small area of north central Iowa.  Winds were sustained around 40 MPH over a four county area with a peak gust of 65 MPH at Steamboat Rock in Hardin County.

Flash Flood in MARSHALL, IOWA
From 26-MAY-13 10:25:00 to 26-MAY-13 11:00:00 (CST-6)
Location: ST ANTHONY
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over Marble Road/County Highway E18 between Canfield Ave and Durham Ave due to the Minerva Creek.

Flash Flood in JASPER, IOWA
From 26-MAY-13 03:03:00 to 26-MAY-13 07:00:00 (CST-6)
Location: KELLOGG
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water covered the road at Illinois Ave and Highway 6.  Parts of Northfield Drive were reported under water with one house surrounded by water.

Hail in AUDUBON, IOWA
From 25-MAY-13 22:23:00 to 25-MAY-13 22:23:00 (CST-6)
Location: FISCUS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Pea to nickel size hail occurring.

Flash Flood in JASPER, IOWA
From 26-MAY-13 04:30:00 to 26-MAY-13 04:30:00 (CST-6)
Location: KELLOGG
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reports sandbagging of the Kellogg water treatment plant and fire department.

Flash Flood in JASPER, IOWA
From 26-MAY-13 03:03:00 to 26-MAY-13 07:00:00 (CST-6)
Location: TURNER
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Highway 6 was under water and closed.  Numerous cars were stalled.

Heavy Rain in HARDIN, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: IOWA FALLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.72 inches.

Heavy Rain in STORY, IOWA
From 26-MAY-13 07:00:00 to 26-MAY-13 07:00:00 (CST-6)
Location: ZEARING
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.33 inches, total 3.17 over two days.

Heavy Rain in HANCOCK, IOWA
From 26-MAY-13 07:00:00 to 26-MAY-13 07:00:00 (CST-6)
Location: KANAWHA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.96 inches, total of 2.44 over the past two days.

Heavy Rain in GRUNDY, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: GRUNDY CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.44 inches.

Flash Flood in HARDIN, IOWA
From 26-MAY-13 10:15:00 to 26-MAY-13 14:00:00 (CST-6)
Location: ABBOTT CROSSING
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over County Highway S56 near the 140th St intersection.

Hail in AUDUBON, IOWA
From 25-MAY-13 22:03:00 to 25-MAY-13 22:03:00 (CST-6)
Location: AUDUBON
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy Rain in DAVIS, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: BLOOMFIELD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 2.04 inches in past two days, 1.90 in the past 24 hours.

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 09:16:00 to 26-MAY-13 12:30:00 (CST-6)
Location: BRADFORD
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Highway 65 at 50th street washed out west of Mallard Ave.

High Wind in HARDIN, IOWA
From 26-MAY-13 10:30:00 to 26-MAY-13 11:30:00 (CST-6)
Magnitude: 56.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Mesonet

Flash Flood in MARSHALL, IOWA
From 26-MAY-13 10:00:00 to 26-MAY-13 11:00:00 (CST-6)
Location: MARSHALLTOWN ARPT
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over Weise Garden Road just north of Marshalltown due to Burnett Creek.

Heavy Rain in JASPER, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: NEWTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 4.18 inches over the past two days.

Heavy Rain in HANCOCK, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: BRITT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 1.36 Inches over the past two days.

Heavy Rain in FRANKLIN, IOWA
From 26-MAY-13 07:00:00 to 26-MAY-13 07:00:00 (CST-6)
Location: HAMPTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.86 inches, two day total of 2.09 inches.

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 08:11:00 to 26-MAY-13 08:11:00 (CST-6)
Location: POPEJOY
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Six inches of water over 70th Ave near the Heather Ave intersection.

Flash Flood in GRUNDY, IOWA
From 26-MAY-13 10:00:00 to 26-MAY-13 14:00:00 (CST-6)
Location: IVESTER
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Highway 14 closed due to water over the road about 3 miles south of Highway 175.  Officials had to rescue one person stranded in a vehicle.

Heavy Rain in JASPER, IOWA
From 26-MAY-13 06:23:00 to 26-MAY-13 06:23:00 (CST-6)
Location: CLYDE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 4 inches of rain in the past 24 hours.

Heavy Rain in TAMA, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: TOLEDO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.47 inches.

Flash Flood in POWESHIEK, IOWA
From 26-MAY-13 07:00:00 to 26-MAY-13 07:00:00 (CST-6)
Location: MALCOLM
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Bridge washed out on Highway 63 north of Montezuma.

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 10:36:00 to 26-MAY-13 11:30:00 (CST-6)
Location: HAMPTON MUNI ARPT
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Highway 65 near County HIghway C47 about 4 miles south of Hampton closed due to Maynes Creek.

Flash Flood in GRUNDY, IOWA
From 26-MAY-13 10:00:00 to 26-MAY-13 14:00:00 (CST-6)
Location: WELLSBURG
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Exit ramps closed at the 187 mile marker on Highway 20 due to water over the road at County Road T19.

Flash Flood in HARDIN, IOWA
From 26-MAY-13 10:15:00 to 26-MAY-13 14:00:00 (CST-6)
Location: EAGLE CITY
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

P Ave washed out near 155th street.

Heavy Rain in JASPER, IOWA
From 26-MAY-13 04:00:00 to 26-MAY-13 04:00:00 (CST-6)
Location: TURNER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Measured 4.4 inches of rain overnight.

Heavy Rain in BUTLER, IOWA
From 26-MAY-13 09:30:00 to 26-MAY-13 09:30:00 (CST-6)
Location: PARKERSBURG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 2.78 inches.

Flash Flood in POWESHIEK, IOWA
From 26-MAY-13 07:00:00 to 26-MAY-13 07:00:00 (CST-6)
Location: GRINNELL ARPT
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Bridge washed out along 390th Ave near 70th St block just west of Malcom.

Flash Flood in POWESHIEK, IOWA
From 26-MAY-13 05:20:00 to 26-MAY-13 07:00:00 (CST-6)
Location: GRINNELL
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Roads in the city covered with water and impassible.

Heavy Rain in POWESHIEK, IOWA
From 26-MAY-13 09:15:00 to 26-MAY-13 09:15:00 (CST-6)
Location: GRINNELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 4.5 inches of rain since 1700 CST Saturday.

Heavy Rain in POWESHIEK, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: GRINNELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 6.74 inches.

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 08:28:00 to 26-MAY-13 12:30:00 (CST-6)
Location: BRADFORD
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over Nettle Ave between 3rd and 5th St in Bradford.

High Wind in WRIGHT, IOWA
From 26-MAY-13 10:30:00 to 26-MAY-13 11:30:00 (CST-6)
Magnitude: 36.00 MS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 09:09:00 to 26-MAY-13 12:30:00 (CST-6)
Location: LATIMER
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over Jonquil Ave about 1.5 miles north of Highway 3 due to flooding of Spring Creek.

Heavy Rain in POWESHIEK, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: MONTEZUMA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 3.96 inches.

High Wind in HAMILTON, IOWA
From 26-MAY-13 10:30:00 to 26-MAY-13 11:30:00 (CST-6)
Magnitude: 36.00 ES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Flash Flood in FRANKLIN, IOWA
From 26-MAY-13 09:10:00 to 26-MAY-13 12:30:00 (CST-6)
Location: COULTER
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Bridge closed on Indigo Ave just south of 110th St due to creek out of its banks.

Heavy Rain in MARSHALL, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: MARSHALLTOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 3.31 inches.

High Wind in FRANKLIN, IOWA
From 26-MAY-13 10:30:00 to 26-MAY-13 11:30:00 (CST-6)
Magnitude: 36.00 ES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Heavy Rain in BUTLER, IOWA
From 26-MAY-13 06:00:00 to 26-MAY-13 06:00:00 (CST-6)
Location: ELEANOR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Twenty four hour rainfall total of 1.92 inches.