An old frontal boundary remained nearly stationary across Iowa, extending from central Kansas northeast into central Iowa.  A strong surge of moisture took place over Kansas with dew points in the low to mid 70s pushing over the frontal boundary.  Dew points rebounded across Iowa to near 70 by the afternoon.  The airmass was very unstable to the southwest of the state with CAPE values approaching 5000 J/kg and lifted indices near -15 C.  Thunderstorms erupted around mid day to the west of Iowa and advanced into the state during the afternoon.  The small cluster of storms took on a bow configuration and produced high winds over a large area as it lifted east-northeast across the state.  There was one injury recorded in Union County at Afton.  A large tree was blown over and hit a man.  He was injured, receiving a punctured long and head injuries.  In another wind incident, a semi-tractortrailer was blown over on Interstate 35 about 3 miles south of Clear Lake.

Thunderstorm Wind in PALO ALTO, IOWA
From 12-JUN-04 15:09:00 to 12-JUN-04 15:09:00 (CST)
Location: MALLARD
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in POLK, IOWA
From 12-JUN-04 15:15:00 to 12-JUN-04 15:15:00 (CST)
Location: ALLEMAN
Magnitude: 50 EG
Property damage: 1K
Reported by: AMATEUR RADIO

Thunderstorm Wind in STORY, IOWA
From 12-JUN-04 15:15:00 to 12-JUN-04 15:15:00 (CST)
Location: CAMBRIDGE
Magnitude: 52 EG
Property damage: 5K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in CERRO GORDO, IOWA
From 12-JUN-04 16:30:00 to 12-JUN-04 16:30:00 (CST)
Location: MASON CITY
Magnitude: 55 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WORTH, IOWA
From 12-JUN-04 16:45:00 to 12-JUN-04 16:45:00 (CST)
Location: KENSETT
Magnitude: 52 EG
Property damage: 2K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in DALLAS, IOWA
From 12-JUN-04 14:26:00 to 12-JUN-04 14:26:00 (CST)
Location: PERRY
Magnitude: 59 EG
Property damage: 5K
Reported by: GENERAL PUBLIC

Thunderstorm Wind in BOONE, IOWA
From 12-JUN-04 14:40:00 to 12-JUN-04 14:40:00 (CST)
Location: BOONE
Magnitude: 50 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in STORY, IOWA
From 12-JUN-04 14:53:00 to 12-JUN-04 14:53:00 (CST)
Location: SLATER
Magnitude: 57 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in GUTHRIE, IOWA
From 12-JUN-04 14:10:00 to 12-JUN-04 14:10:00 (CST)
Location: JAMAICA
Magnitude: 61 EG
Property damage: 2K
Reported by: NWS EMPLOYEE(OFF DUTY)

Thunderstorm Wind in STORY, IOWA
From 12-JUN-04 15:08:00 to 12-JUN-04 15:08:00 (CST)
Location: AMES
Magnitude: 55 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in GREENE, IOWA
From 12-JUN-04 14:55:00 to 12-JUN-04 14:55:00 (CST)
Location: CHURDAN
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in POLK, IOWA
From 12-JUN-04 15:15:00 to 12-JUN-04 15:15:00 (CST)
Location: DES MOINES
Magnitude: 50 EG
Property damage: 5K
Reported by: AMATEUR RADIO

Thunderstorm Wind in ADAIR, IOWA
From 12-JUN-04 14:00:00 to 12-JUN-04 14:00:00 (CST)
Location: GREENFIELD
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in BLACK HAWK, IOWA
From 12-JUN-04 16:45:00 to 12-JUN-04 16:45:00 (CST)
Location: CEDAR FALLS
Magnitude: 50 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in UNION, IOWA
From 12-JUN-04 14:15:00 to 12-JUN-04 14:15:00 (CST)
Location: AFTON
Magnitude: 50 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT

A tree was blown over and injured one person.  He received a punctured lung and head injuries.

Thunderstorm Wind in DALLAS, IOWA
From 12-JUN-04 14:25:00 to 12-JUN-04 14:25:00 (CST)
Location: PERRY
Magnitude: 50 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in CERRO GORDO, IOWA
From 12-JUN-04 16:45:00 to 12-JUN-04 16:45:00 (CST)
Location: CLEAR LAKE
Magnitude: 61 EG
Property damage: 10K
Reported by: TRAINED SPOTTER