A very hot airmass was in place over Iowa, though it was capped through the daytime hours.  High temperatures reached the mid to upper 90s in the north and 100 to 108 across the south.  A cold front moved into northwest Iowa during the afternoon.  Dewpoint temperatures pooled along the front to the 65 to 70 degree range.  The atmosphere became unstable with the lifted index falling to around -5 C and CAPE increasing to between 2000 and 4000 J/kg.  CAPE in the -10 to -30 C layer of the atmosphere was between 400 and 700 J/kg, but the freezing level was around 15,000 feet and shear 20 kts or less.  Precipitable water values were high at around 2 inches.  The primary mode of severe weather was high winds.  A line of thunderstorms formed along the cold front during the early evening hours, rapid intensification once they broke through the cap.  The storms became cold pool dominated by mid evening with the outflow boundary leading the storms by about 30 miles.  Most of the storms produced winds of 50 to 60 MPH, with a few gusts of 65 to 75 MPH.  The highest winds were in Carroll and Poweshiek Counties.  Downdraft CAPE was between 1200 and 1800 J/kg.  There was little tornado threat with the LCL between 2500 and 3500 meters.  There were a few reports of hail, but most of the hail was under an inch in diameter and not a primary event.  One report of golf ball size hail was received from the Ruthven area in Palo Alto County.  Winds caused numerous power outages and also damaged many trees.  As a storm moved through Boone County, the Central Iowa Expo building was flattened. It was under construction with three sides of the building completed. High winds at the Ames Airport flipped a plane over from the same storm that moved through Boone County.

Thunderstorm Wind in JASPER, IOWA
From 25-JUL-12 20:09:00 to 25-JUL-12 20:09:00 (CST-6)
Location: COLFAX
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines down in Colfax.

Thunderstorm Wind in MADISON, IOWA
From 25-JUL-12 19:27:00 to 25-JUL-12 19:27:00 (CST-6)
Location: EARLHAM
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Reported by the Earlham police department.

Hail in PALO ALTO, IOWA
From 25-JUL-12 17:36:00 to 25-JUL-12 17:36:00 (CST-6)
Location: DEPEW
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in FRANKLIN, IOWA
From 25-JUL-12 19:40:00 to 25-JUL-12 19:40:00 (CST-6)
Location: ALEXANDER
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Corn bins were blown onto the road.

Thunderstorm Wind in WEBSTER, IOWA
From 25-JUL-12 18:45:00 to 25-JUL-12 18:45:00 (CST-6)
Location: (FOD)FT DODGE MUNI A
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tree branches of six to eight inches in diameter were down.  Numerous other branches broken in town.

Hail in POLK, IOWA
From 25-JUL-12 20:14:00 to 25-JUL-12 20:14:00 (CST-6)
Location: SWANWOOD
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Amateur Radio

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:48:00 to 25-JUL-12 18:48:00 (CST-6)
Location: CARROLL
Magnitude: 55.00 MG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in CARROLL, IOWA
From 25-JUL-12 18:55:00 to 25-JUL-12 18:55:00 (CST-6)
Location: BREDA
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: State Official

One inch hail was reported along with crop damage.

Thunderstorm Wind in WEBSTER, IOWA
From 25-JUL-12 19:10:00 to 25-JUL-12 19:10:00 (CST-6)
Location: FARNHAMVILLE
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tree branches blown down.

Hail in PALO ALTO, IOWA
From 25-JUL-12 18:11:00 to 25-JUL-12 18:11:00 (CST-6)
Location: WEST BEND
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Public

Thunderstorm Wind in BOONE, IOWA
From 25-JUL-12 19:31:00 to 25-JUL-12 19:31:00 (CST-6)
Location: BOXHOLM
Magnitude: 50.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Tree limbs of three to four inches in diameter down.

Hail in STORY, IOWA
From 25-JUL-12 20:07:00 to 25-JUL-12 20:07:00 (CST-6)
Location: STORY CITY
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 25-JUL-12 18:20:00 to 25-JUL-12 18:20:00 (CST-6)
Location: ALGONA
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Amateur Radio

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:35:00 to 25-JUL-12 18:35:00 (CST-6)
Location: CARROLL NEU ARPT
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:49:00 to 25-JUL-12 19:49:00 (CST-6)
Location: AMES ARPT
Magnitude: 59.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A plane was flipped at the Ames Airport.

Heavy Rain in EMMET, IOWA
From 25-JUL-12 17:17:00 to 25-JUL-12 17:17:00 (CST-6)
Location: ESTHERVILLE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Minor street flooding reported with wind gusts to 35 MPH and frequent cloud to ground lightning.

Hail in WRIGHT, IOWA
From 25-JUL-12 19:03:00 to 25-JUL-12 19:03:00 (CST-6)
Location: BELMOND
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Nickle to quarter size hail and 50 MPH winds.

Hail in PALO ALTO, IOWA
From 25-JUL-12 17:23:00 to 25-JUL-12 17:23:00 (CST-6)
Location: RUTHVEN
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Thunderstorm Wind in CERRO GORDO, IOWA
From 25-JUL-12 19:30:00 to 25-JUL-12 19:30:00 (CST-6)
Location: THORNTON
Magnitude: 57.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lots of trees down, including one on fire. A few windows were also broken.

Hail in WRIGHT, IOWA
From 25-JUL-12 19:08:00 to 25-JUL-12 19:08:00 (CST-6)
Location: BELMOND
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:40:00 to 25-JUL-12 19:40:00 (CST-6)
Location: MAXWELL
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Power was knocked out in Maxwell.

Thunderstorm Wind in BOONE, IOWA
From 25-JUL-12 19:40:00 to 25-JUL-12 19:40:00 (CST-6)
Location: BOONE MUNI ARPT
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: NWS Employee

Tree damage with a tree on a power line and on fire.

Thunderstorm Wind in POLK, IOWA
From 25-JUL-12 19:39:00 to 25-JUL-12 19:39:00 (CST-6)
Location: POLK CITY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in WRIGHT, IOWA
From 25-JUL-12 19:15:00 to 25-JUL-12 19:15:00 (CST-6)
Location: BELMOND
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in KOSSUTH, IOWA
From 25-JUL-12 18:10:00 to 25-JUL-12 18:10:00 (CST-6)
Location: ALGONA MUNI ARPT
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:37:00 to 25-JUL-12 18:37:00 (CST-6)
Location: GLIDDEN
Magnitude: 44.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Small limbs were breaking with winds estimated of 50 MPH.

Thunderstorm Wind in MARION, IOWA
From 25-JUL-12 20:30:00 to 25-JUL-12 20:30:00 (CST-6)
Location: RED ROCK
Magnitude: 64.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

An IDOT wind sensor along the bridge recorded winds of 74 MPH.  Winds possibly higher than adjacent areas due to sensor sighting.

Thunderstorm Wind in BOONE, IOWA
From 25-JUL-12 19:46:00 to 25-JUL-12 19:46:00 (CST-6)
Location: PLEASANT HILL
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds estimated of 55 to 60 MPH.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:50:00 to 25-JUL-12 19:50:00 (CST-6)
Location: AMES
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: NWS Employee

Large tree limb of about a foot in diameter was down on the ISU campus, along with several three to four inch diameter branches.

Thunderstorm Wind in WEBSTER, IOWA
From 25-JUL-12 19:10:00 to 25-JUL-12 19:10:00 (CST-6)
Location: GOWRIE
Magnitude: 61.00 EG
Property damage: 25.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Many tree branches down in town, some blocking streets.  Amstar sign just hanging to its base.  Winds were estimated of 70 MPH.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:54:00 to 25-JUL-12 19:54:00 (CST-6)
Location: ROLAND
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Six inch tree branch down in Roland with several other branches of three to six inch diameter downed.

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:55:00 to 25-JUL-12 18:55:00 (CST-6)
Location: LANESBORO
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 50.00K
Reported by: State Official

Power lines down.

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 19:00:00 to 25-JUL-12 19:00:00 (CST-6)
Location: ARCADIA
Magnitude: 61.00 EG
Property damage: 75.00K
Crop damage: 50.00K
Reported by: Emergency Manager

A few three foot diameter trees were downed.  A 30 foot long camper attached to a truck was blown over.  Several crops damaged.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:57:00 to 25-JUL-12 19:57:00 (CST-6)
Location: STORY CITY
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency Manager estimated winds of 60 MPH.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:51:00 to 25-JUL-12 19:51:00 (CST-6)
Location: STORY CITY
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Two to three inch diameter trees down.

Thunderstorm Wind in GREENE, IOWA
From 25-JUL-12 19:00:00 to 25-JUL-12 19:00:00 (CST-6)
Location: JEFFERSON
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Trained Spotter

One and one half foot diameter trees down and corn flattened.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:53:00 to 25-JUL-12 19:53:00 (CST-6)
Location: NEVADA
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Three to four inch diameter tree down at the intersection of 8th and H.  Crews working on it at the time.  Other small branches were down and a trash can lid was blown off of a concrete bin.  Five to six inch tree snapped at the East Park.

Thunderstorm Wind in CALHOUN, IOWA
From 25-JUL-12 18:49:00 to 25-JUL-12 18:49:00 (CST-6)
Location: LOHRVILLE
Magnitude: 61.00 EG
Property damage: 25.00K
Crop damage: 15.00K
Reported by: AWOS

Big limbs down everywhere.  Casey's diesel pump blown over and laying on its side.  A tree was laying on top of a car.  Some crop damage also reported.

Thunderstorm Wind in BOONE, IOWA
From 25-JUL-12 19:31:00 to 25-JUL-12 19:31:00 (CST-6)
Location: OGDEN
Magnitude: 52.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency Manager estimated winds of 60 MPH.  Central Iowa Expo building was destroyed.

Thunderstorm Wind in CALHOUN, IOWA
From 25-JUL-12 18:53:00 to 25-JUL-12 18:53:00 (CST-6)
Location: ROCKWELL CITY
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Branches and power lines down in the area.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 20:04:00 to 25-JUL-12 20:04:00 (CST-6)
Location: ROLAND
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Sixty MPH winds along with pea size hail were reported.  There was a secondary report of wind damage in the Gilbert area.

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:37:00 to 25-JUL-12 18:37:00 (CST-6)
Location: CARROLL
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Widespread damage throughout the town of Carroll.  Numerous branches, power lines, and street signs down.

Hail in HANCOCK, IOWA
From 25-JUL-12 18:55:00 to 25-JUL-12 18:55:00 (CST-6)
Location: BRITT
Magnitude: 1.00 
Property damage: 10.00K
Crop damage: 50.00K
Reported by: State Official

Crop damage in Britt and street signs down in town.

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:55:00 to 25-JUL-12 18:55:00 (CST-6)
Location: CARROLL
Magnitude: 65.00 EG
Property damage: 25.00K
Crop damage: 50.00K
Reported by: State Official

Power lines down in Carroll.  Large branches down, causing damage to a house porch.

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 20:03:00 to 25-JUL-12 20:03:00 (CST-6)
Location: COLO
Magnitude: 58.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 20:05:00 to 25-JUL-12 20:05:00 (CST-6)
Location: HUXLEY
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Power lines were down.

Thunderstorm Wind in POWESHIEK, IOWA
From 25-JUL-12 21:02:00 to 25-JUL-12 21:02:00 (CST-6)
Location: BROOKLYN
Magnitude: 57.00 MG
Property damage: 3.00K
Crop damage: 5.00K
Reported by: Mesonet

Thunderstorm Wind in GRUNDY, IOWA
From 25-JUL-12 20:38:00 to 25-JUL-12 20:38:00 (CST-6)
Location: CONRAD
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree snapped in half by high winds.

Thunderstorm Wind in WEBSTER, IOWA
From 25-JUL-12 19:12:00 to 25-JUL-12 19:12:00 (CST-6)
Location: GOWRIE
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Branches broken by winds in the city park.

Thunderstorm Wind in MARSHALL, IOWA
From 25-JUL-12 19:37:00 to 25-JUL-12 19:37:00 (CST-6)
Location: HAVERHILL
Magnitude: 56.00 MG
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Storm Chaser

Sustained winds of 65 MPH measured with an anemometer.  Penny size hail also reported.

Thunderstorm Wind in MARSHALL, IOWA
From 25-JUL-12 19:43:00 to 25-JUL-12 19:43:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in KOSSUTH, IOWA
From 25-JUL-12 18:20:00 to 25-JUL-12 18:20:00 (CST-6)
Location: ALGONA
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Branches blown down by high winds.

Thunderstorm Wind in BOONE, IOWA
From 25-JUL-12 19:15:00 to 25-JUL-12 19:15:00 (CST-6)
Location: BOXHOLM
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds of 60 to 65 MPH were estimated in Boxholm.  Multiple three to four inch diameter tree limbs down.  Several transformers blown.

Thunderstorm Wind in WEBSTER, IOWA
From 25-JUL-12 19:40:00 to 25-JUL-12 19:40:00 (CST-6)
Location: CALLENDER
Magnitude: 50.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Several five inch diameter tree limbs down throughout Callendar.

Thunderstorm Wind in HAMILTON, IOWA
From 25-JUL-12 20:12:00 to 25-JUL-12 20:12:00 (CST-6)
Location: JEWELL
Magnitude: 61.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in STORY, IOWA
From 25-JUL-12 19:50:00 to 25-JUL-12 19:50:00 (CST-6)
Location: AMES ARPT
Magnitude: 59.00 MG
Property damage: 10.00K
Crop damage: 5.00K
Reported by: ASOS

Thunderstorm Wind in WRIGHT, IOWA
From 25-JUL-12 18:55:00 to 25-JUL-12 18:55:00 (CST-6)
Location: EAGLE GROVE
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Six to 8 inch diameter limbs down.

Thunderstorm Wind in HUMBOLDT, IOWA
From 25-JUL-12 18:35:00 to 25-JUL-12 18:35:00 (CST-6)
Location: BROCK RANCH ARPT
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large six to eight inch diameter tree branches down.  Dime size hail also reported.

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 19:10:00 to 25-JUL-12 19:10:00 (CST-6)
Location: LIDDERDALE
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Multiple four to six inch diameter branches down.

Thunderstorm Wind in KOSSUTH, IOWA
From 25-JUL-12 18:05:00 to 25-JUL-12 18:05:00 (CST-6)
Location: ALGONA
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in CARROLL, IOWA
From 25-JUL-12 18:40:00 to 25-JUL-12 18:40:00 (CST-6)
Location: BREDA
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Multiple branches down throughout the town of Breda.  Generally an inch in diameter.