Strong warm air advection took place over Iowa during the night of the 22nd into the morning of the 23rd.  A low level jet of over 40 kts developed, transporting moisture into the state.  Precipitable water values increased to between 1.7 and 2 inches over northwest into central Iowa.  CAPE was in the 2000 to 4000 J/kg range to the southwest of the precipitable water maximum, with lifted indices of -6 to -10.  Thunderstorms formed over South Dakota and moved into northwest and north central Iowa.  The storms produced both hail and high winds as they advanced into the state.  Downdraft CAPE was quite high with 1200 to 1400 J/kg available.  CAPE in the -10 to -30 C layer of the atmosphere was between 500 and 1000 J/kg, however a very high freezing level limited the size of the hail as the freezing level was around 15,000 feet.  The atmosphere was moderately sheared with 35 to 45 kts of shear available.  By far the predominant mode of severe weather was the high winds.  Trees were uprooted in Palo Alto County at Emmetsburg.  Several other reports of winds of 60 to 70 MPH were received in Palo Alto and Kossuth County.  A mesonet station northeast of Whittemore recorded a 75 MPH wind gust, with 68 MPH winds recorded at the Algona Airport for example.  In Webster County, one inch diameter hail fell north of the Fort Dodge Airport.  As the thunderstorms progressed eastward, the intensity diminished.  There were spotty reports of high winds and hail across north central and parts of northeast Iowa.  Scattered thunderstorms developed behind the main area before sunrise.  For the most part they were not severe, but did produce high winds and some nickel to quarter size hail.

Thunderstorm Wind in HAMILTON, IOWA
From 23-AUG-11 02:36:00 to 23-AUG-11 02:36:00 (CST-6)
Location: WEBSTER CITY
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Extensive tree damage throughout the town of Webster City.  Multiple tree limbs down, each about a foot in diameter.

Thunderstorm Wind in HANCOCK, IOWA
From 23-AUG-11 02:00:00 to 23-AUG-11 02:00:00 (CST-6)
Location: BRITT
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Newspaper

High winds blew down trees and power lines.

Hail in HAMILTON, IOWA
From 23-AUG-11 05:06:00 to 23-AUG-11 05:06:00 (CST-6)
Location: KAMRAR
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in WORTH, IOWA
From 23-AUG-11 05:58:00 to 23-AUG-11 05:58:00 (CST-6)
Location: NORTHWOOD MUNI ARPT
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 150.00K
Reported by: Trained Spotter

A few 4 to 6 inch diameter limbs down.  Extensive corn and bean crop damage.

Hail in HAMILTON, IOWA
From 23-AUG-11 04:57:00 to 23-AUG-11 04:57:00 (CST-6)
Location: KAMRAR
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 20.00K
Reported by: Public

Thunderstorm Wind in KOSSUTH, IOWA
From 23-AUG-11 01:40:00 to 23-AUG-11 01:40:00 (CST-6)
Location: ALGONA
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Considerable tree damage in town.  Many roads impassable.

Hail in HAMILTON, IOWA
From 23-AUG-11 04:52:00 to 23-AUG-11 04:52:00 (CST-6)
Location: WEBSTER CITY ARPT
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Thunderstorm Wind in KOSSUTH, IOWA
From 23-AUG-11 01:35:00 to 23-AUG-11 01:35:00 (CST-6)
Location: WHITTEMORE
Magnitude: 65.00 MG
Property damage: 25.00K
Crop damage: 50.00K
Reported by: Mesonet

Thunderstorm Wind in PALO ALTO, IOWA
From 23-AUG-11 01:14:00 to 23-AUG-11 01:14:00 (CST-6)
Location: EMMETSBURG
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Numerous trees uprooted in town.  Some minor flooding was also noted.

Thunderstorm Wind in KOSSUTH, IOWA
From 23-AUG-11 01:40:00 to 23-AUG-11 01:40:00 (CST-6)
Location: ALGONA MUNI ARPT
Magnitude: 59.00 MG
Property damage: 10.00K
Crop damage: 5.00K
Reported by: ASOS

Thunderstorm Wind in PALO ALTO, IOWA
From 23-AUG-11 01:14:00 to 23-AUG-11 01:14:00 (CST-6)
Location: EMMETSBURG
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Patio furniture was blown around and branches were down in the yard.

Thunderstorm Wind in KOSSUTH, IOWA
From 23-AUG-11 01:37:00 to 23-AUG-11 01:37:00 (CST-6)
Location: ALGONA
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines were down around town.

Hail in WEBSTER, IOWA
From 23-AUG-11 02:20:00 to 23-AUG-11 02:20:00 (CST-6)
Location: (FOD)FT DODGE MUNI A
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Thunderstorm Wind in WORTH, IOWA
From 23-AUG-11 05:52:00 to 23-AUG-11 05:52:00 (CST-6)
Location: JOICE
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees down partially blocking the road near the intersection of Willow and Main Street.