A seasonally strong cold front moved southeast into the state during the afternoon and evening hours of the 28th.  There was a strong contrast across the front with highs in the low 90s south of the front with dew points in the low to mid 70s, and temperatures in the 60s and 70s north of the front.  The airmass was quite unstable with CAPE between 3000 and 4000 J/kg and lifted indices in the -6 to -8 C. range.  There was sufficient shear in place and was in the 35 to 50 kt range.  CAPE in the -10 to -30 C. layer of the atmosphere was 500 to 700 J/kg, however with freezing levels 15,000 to 15,500 feet hail was not realized in severe size at the ground level.  The LCL was between 1000 and 1500 meters along the lead edge of the thunderstorms.  As the front progressed southeast, a line of thunderstorms developed just ahead of the front.  They developed quite rapidly as the cap was broken.  The air was fairly dry in the lower levels leading to downdraft CAPE of 1000 to 1500 J/kg.    In spite of the dry layer at low levels, precipitable water values were quite high, in the 1.5 to 1.7 inch range.  Many of the storms remained below severe levels.  An upper level vorticity max lifted northeast across eastern Nebraska into western Iowa during the late afternoon and evening hours.  This intensified storms over eastern Nebraska, which moved into western Iowa.  The storms became severe and produced high winds and several tornadoes from west central into central Iowa.  The line took on a very evident bow echo as it moved through Crawford County, and that remained in tact as far east as Story County.  Numerous reports of tree damage and power line damage were received, with winds of 60 to 70 MPH common.  Winds were strong enough to partially blow over a utility pole near Jamaica in Guthrie County.  A semitrailer truck was blown off off of County Road E-57 west of Kelly in Story County.  Tornadoes touched down in Carroll and Greene Counties.  They were short lived and were only on the ground for a short time in rural areas.  One of them touched down in Carroll County north of Dedham, while a short time later a second touched down north of Coon Rapids downing utility poles.  An aerial survey showed a very intermittent track, beginning about 3 miles north of Coon Rapids in Carroll County, continuing east for approximately 15 miles.  It dissipated in Greene County just west of Cooper.  Maximum path width was 50 yards.  Crop damage and power poles were bent but no structures were significantly impacted.  There was a two mile continuous swath of corn damage occurring about four miles west of Cooper with numerous meanders and turns.  EF0 damage ended at approximately 1825 PM CST.  Another tornado was on the ground for about 5 minutes in an intermittent track from southwest to south of Rippey.  Minor roof damage was done and some windows were blown out by the tornado southwest of Rippey.  Another tornado touched down in Guthrie County west of Bayard.  An aerial survey showed a 3/4 mile long track that was embedded in the west to east outflow of the storm.  A 50 yard wide track of damaged corn and a dozen trees downed at a farmstead were observed.  A few shingles were blown off the house, but otherwise no other significant building damage was noted.  The tornado was and EF0.  Flash flooding was also a concern with flash flooding taking place in Calhoun and Wright Counties.  Water was flowing over roads and into some basements.  Heavy rainfall of 1 to 2 inches was common over already saturated ground.  Nearly three and one half inches /3.42/ fell in a short time in the Rockwell City area.

Flash Flood in CALHOUN, IOWA
From 28-AUG-07 19:57:00 to 28-AUG-07 20:51:00 (CST-6)
Location: YETTER
Flood cause: Heavy Rain
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Six inches of water was reported in basements due to heavy rain.  Numerous basements were flooded.

Thunderstorm Wind in CRAWFORD, IOWA
From 28-AUG-07 17:15:00 to 28-AUG-07 17:15:00 (CST-6)
Location: DENISON MUNI ARPT
Magnitude: 55.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: AWOS

Tornado in GREENE, IOWA
From 28-AUG-07 18:05:00 to 28-AUG-07 18:25:00 (CST-6)
Location: COOPER
Tornado F-scale: EF0
Property damage: 10.00K
Crop damage: 50.00K
Reported by: Broadcast Media

An aerial survey showed very intermittent track that began 3 miles north of Coon Rapids, in Carroll County, and continued east, into Greene County, for  approximately 15 miles, dissipating near Cooper. The maximum width was 50 yards. Crop damage was reported and power poles bent but no  structures were impacted. A two mile continuous swath of corn damage occurred 4 miles west of Cooper with numerous meanders and turns.  The strength was EF0 ending at approximately 1825CST.

Tornado in GUTHRIE, IOWA
From 28-AUG-07 18:02:00 to 28-AUG-07 18:03:00 (CST-6)
Location: BAYARD
Tornado F-scale: EF0
Property damage: 20.00K
Crop damage: 10.00K
Reported by: Broadcast Media

An aerial survey showed a 3/4 mile long track embedded in west to east outflow. A 50 yard wide track damaged corn was observed.  It also downed a dozen trees at a farmstead. A few shingles were blown off the house otherwise no building damage. The strength was EF0.

Flash Flood in CALHOUN, IOWA
From 28-AUG-07 17:34:00 to 28-AUG-07 20:51:00 (CST-6)
Location: YETTER
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Heavy rainfall resulted in water running over highways with ditches full.

Flash Flood in WRIGHT, IOWA
From 28-AUG-07 17:51:00 to 28-AUG-07 19:57:00 (CST-6)
Location: GOLDFIELD
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Water was reported running over highways in and around Eagle Grove with widespread street flooding.

Flash Flood in CALHOUN, IOWA
From 28-AUG-07 19:57:00 to 28-AUG-07 20:51:00 (CST-6)
Location: KNOKE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous vehicles were stranded in flooded streets in Rockwell City.

Tornado in CARROLL, IOWA
From 28-AUG-07 17:58:00 to 28-AUG-07 17:58:00 (CST-6)
Location: DEDHAM
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Tornado touched down briefly between Willey and Dedham.

Tornado in CARROLL, IOWA
From 28-AUG-07 18:00:00 to 28-AUG-07 18:05:00 (CST-6)
Location: COON RAPIDS
Tornado F-scale: EF0
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Telephone poles were down as a result of the tornado.  The tornado moved from Carroll County into Greene County.

Tornado in GREENE, IOWA
From 28-AUG-07 18:29:00 to 28-AUG-07 18:34:00 (CST-6)
Location: ANGUS
Tornado F-scale: EF0
Property damage: 20.00K
Crop damage: 25.00K
Reported by: Law Enforcement

The tornado caused minor roof damage with some windows blown out 5 miles southwest of Rippey.  The tornado touched down on at least two separate times on an intermittent path.

Thunderstorm Wind in CRAWFORD, IOWA
From 28-AUG-07 17:15:00 to 28-AUG-07 17:15:00 (CST-6)
Location: DENISON
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

High winds in excess of 60 MPH downed trees and power lines.

Thunderstorm Wind in CRAWFORD, IOWA
From 28-AUG-07 17:19:00 to 28-AUG-07 17:19:00 (CST-6)
Location: DENISON
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CRAWFORD, IOWA
From 28-AUG-07 17:26:00 to 28-AUG-07 17:26:00 (CST-6)
Location: DENISON
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter estimated winds of 55 to 60 MPH and had several large tree limbs down, including at least one 10 inch diameter limb.

Thunderstorm Wind in CARROLL, IOWA
From 28-AUG-07 17:55:00 to 28-AUG-07 17:55:00 (CST-6)
Location: GLIDDEN
Magnitude: 57.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

High winds downed trees in town, one was on fire as it came in contact with a power line.

Thunderstorm Wind in CARROLL, IOWA
From 28-AUG-07 18:00:00 to 28-AUG-07 18:00:00 (CST-6)
Location: COON RAPIDS
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 10.00K
Reported by: Emergency Manager

Strong winds blew a barn over.

Thunderstorm Wind in AUDUBON, IOWA
From 28-AUG-07 18:02:00 to 28-AUG-07 18:02:00 (CST-6)
Location: AUDUBON
Magnitude: 57.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Winds blew down a few large trees and several 5 to 10 inch diameter limbs were downed in Audubon.

Thunderstorm Wind in STORY, IOWA
From 28-AUG-07 19:00:00 to 28-AUG-07 19:00:00 (CST-6)
Location: KELLEY
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Law Enforcement

A semi truck was blown off road on E57.

Thunderstorm Wind in STORY, IOWA
From 28-AUG-07 19:10:00 to 28-AUG-07 19:10:00 (CST-6)
Location: AMES
Magnitude: 52.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Ames police reported several large trees down along Country Club Blvd. One power pole was down with other damage near the corner of State and Mortenson roads.

Thunderstorm Wind in SAC, IOWA
From 28-AUG-07 16:00:00 to 28-AUG-07 16:00:00 (CST-6)
Location: SCHALLER
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Four to five inch tree branches were downed by high winds.

Thunderstorm Wind in CRAWFORD, IOWA
From 28-AUG-07 17:18:00 to 28-AUG-07 17:18:00 (CST-6)
Location: DELOIT
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CARROLL, IOWA
From 28-AUG-07 17:44:00 to 28-AUG-07 17:44:00 (CST-6)
Location: TEMPLETON
Magnitude: 50.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter measured wind gusts up to 58 mph.

Thunderstorm Wind in CARROLL, IOWA
From 28-AUG-07 17:44:00 to 28-AUG-07 17:44:00 (CST-6)
Location: TEMPLETON
Magnitude: 59.00 MG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A 50 year old large tree was blown down along with several other limbs covering the roads in the town of Templeton.

Thunderstorm Wind in GUTHRIE, IOWA
From 28-AUG-07 18:25:00 to 28-AUG-07 18:25:00 (CST-6)
Location: JAMAICA
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

A power pole was partially blown over.

Thunderstorm Wind in STORY, IOWA
From 28-AUG-07 19:20:00 to 28-AUG-07 19:20:00 (CST-6)
Location: ONTARIO
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter