A frontal boundary extended southwest to northeast across Iowa during the early morning hours of the 15th.  At the same time, a large MCS developed over northern Nebraska and tracked east into southern Minnesota into northern Iowa.  The airmass was quite unstable over Iowa and favorable for elevated convection as the system moved in.  CAPE values remained in the 2000 to 3500 J/kg range along and south of the boundary with lifted indices in the -8 range.  The environment was quite strongly sheared with 50 to 60 kts of shear. The downdraft CAPE was in the 500 to 700 J/kg range.  Thunderstorms intensified as they moved across Iowa with a small bow echo element developing as the MCS began to interact with the frontal boundary.  The event took shape as it moved into north central Iowa and produced 60 to 70 MPH winds as it moved from Kossuth County, east-southeast toward Tama County.  Hail was limited with the event as the freezing level had not changed much from the previous day and was still in the 15,500 foot range.  One report of three-quarter inch diameter hail was received from Franklin County.  There were numerous reports of tree and power line damage.  Two semitrailer trucks were blown off of Interstate 35 in southwest Cerro Gordo County between mile post 185 and 186.  The two drivers received minor injuries.  Reported wind damage included several out buildings and at least two barns flattened by high winds. Some of the harder hit areas were in Bremer County in the Plainfield area.  Barns were blown down, along with numerous trees and power poles.  The roof of a convenience store was peeled back in Plainfield.  Damage extended along U.S. Highway 218 from Plainfield north to at least the Chickasaw County line.

Thunderstorm Wind in BREMER, IOWA
From 15-AUG-07 07:15:00 to 15-AUG-07 07:15:00 (CST-6)
Location: TRIPOLI
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Thunderstorm Wind in BUTLER, IOWA
From 15-AUG-07 06:40:00 to 15-AUG-07 06:40:00 (CST-6)
Location: CLARKSVILLE
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous trees were blown down, some up to one to two feet in diameter.  One large tree fell on a home causing damage to the home.  Power lines were down on roadways along with the trees.

Thunderstorm Wind in KOSSUTH, IOWA
From 15-AUG-07 04:10:00 to 15-AUG-07 04:10:00 (CST-6)
Location: BURT
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Two power poles downed one half mile north of Burt and tree limbs were downed in Burt.

Thunderstorm Wind in CERRO GORDO, IOWA
From 15-AUG-07 05:49:00 to 15-AUG-07 05:49:00 (CST-6)
Location: ROCKWELL
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 6 to 8 inch tree limbs were blown down, some possibly  larger, were blocking at least 10 roads in the town of Rockwell.

Thunderstorm Wind in HANCOCK, IOWA
From 15-AUG-07 05:00:00 to 15-AUG-07 05:00:00 (CST-6)
Location: BRITT
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in CERRO GORDO, IOWA
From 15-AUG-07 05:20:00 to 15-AUG-07 05:20:00 (CST-6)
Location: VENTURA
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 10.00K
Reported by: Broadcast Media

A garage was picked up with debris deposited on nearby cars. In addition, a two foot diameter tree was blown down.

Thunderstorm Wind in BREMER, IOWA
From 15-AUG-07 06:55:00 to 15-AUG-07 06:55:00 (CST-6)
Location: BREMER
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 10 to 12 inch diameter pine tree limbs were blown down.

Thunderstorm Wind in CERRO GORDO, IOWA
From 15-AUG-07 05:20:00 to 15-AUG-07 05:20:00 (CST-6)
Location: VENTURA
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 5.00K
Reported by: Broadcast Media

High winds partially blew down a barn.  The Emergency manager also reported power lines blown down.

Thunderstorm Wind in BREMER, IOWA
From 15-AUG-07 06:52:00 to 15-AUG-07 06:52:00 (CST-6)
Location: PLAINFIELD
Magnitude: 70.00 EG
Property damage: 75.00K
Crop damage: 25.00K
Reported by: Emergency Manager

High winds blew the roof off of a convenience store. The roof flew one block, shearing off power poles and knocking out power to entire town. Trees were blown down on houses in Plainfield.  Trees and power poles were down just west of Plainfield.

Thunderstorm Wind in CERRO GORDO, IOWA
From 15-AUG-07 05:38:00 to 15-AUG-07 05:38:00 (CST-6)
Location: SWALEDALE
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Two semis were blown over between mile markers 185 and 186 on interstate 35.

Thunderstorm Wind in FRANKLIN, IOWA
From 15-AUG-07 06:35:00 to 15-AUG-07 06:35:00 (CST-6)
Location: FAULKNER
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 4 to 6 inch tree limbs were blown down.

Thunderstorm Wind in BUTLER, IOWA
From 15-AUG-07 06:40:00 to 15-AUG-07 06:40:00 (CST-6)
Location: CLARKSVILLE
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Employee

A NWS Employee estimated wind gusts of 65 to 70 mph in the town of  Clarksville.

Thunderstorm Wind in BREMER, IOWA
From 15-AUG-07 07:05:00 to 15-AUG-07 07:05:00 (CST-6)
Location: WAVERLY
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in CERRO GORDO, IOWA
From 15-AUG-07 05:23:00 to 15-AUG-07 05:23:00 (CST-6)
Location: MESERVEY
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Trained Spotter

The top one quarter of the tree tops were snapped off of 3 large  trees.  One was a cottonwood and 2 locust trees.

Thunderstorm Wind in BREMER, IOWA
From 15-AUG-07 06:55:00 to 15-AUG-07 06:55:00 (CST-6)
Location: PLAINFIELD
Magnitude: 65.00 EG
Property damage: 75.00K
Crop damage: 50.00K
Reported by: Trained Spotter

Numerous trees were blown down along highway 218 from the Chickasaw/Bremer County line, south through at least Plainfield.  Trees were blown down on roads and some homes. Power poles were also blown down on roads. Large areas were without electricity.  a few barns were also blown down.

Thunderstorm Wind in HANCOCK, IOWA
From 15-AUG-07 05:10:00 to 15-AUG-07 05:10:00 (CST-6)
Location: GARNER
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in FRANKLIN, IOWA
From 15-AUG-07 06:30:00 to 15-AUG-07 06:30:00 (CST-6)
Location: FAULKNER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Emergency Manager

Small tree limbs were also reported blown down.