An east to west warm frontal boundary extended from southern Nebraska into extreme southern Iowa.  A strong push of warm and unstable air pushed over the top of the boundary.  Lifted indices were in the -8 to -11 C range with Cape values of 3000 to 5000 J/kg during the event.  Thunderstorms developed over west central and southwest Iowa during the predawn hours.  The area spread east and expanded toward sunrise.  The initial shot produced a few wind gusts in the central counties to around 60 MPH.  Thunderstorms remained below severe limits for a few hours after that.  Another area began to become more intense, aided by the cool pool produced by the first round of convection.  This area progressed east and south, producing wind gusts of 60 to 65 MPH with the stronger storms.  Damage was restricted to tree and power line damage for the most part.  Two barns were destroyed in Davis County south of Bloomfield.  One cell produced hail toward the end of the event.  Hail up to golf ball size fell in the New Virginia area of Warren County.  In the area behind the main thunderstorms, development took place in northwest Iowa.  The thunderstorms trained over Wayne County for two to three hours.  Seven inches of rain fell west of Corydon in that period and caused flash flooding in the area.  Ten inches of rain was flowing over the roads following the rain.

Thunderstorm Wind in MAHASKA, IOWA
From 11-JUL-04 11:55:00 to 11-JUL-04 11:55:00 (CST)
Location: OSKALOOSA
Magnitude: 52 EG
Property damage: 10K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DAVIS, IOWA
From 11-JUL-04 10:15:00 to 11-JUL-04 10:15:00 (CST)
Location: BLOOMFIELD
Magnitude: 52 EG
Property damage: 1K
Reported by: OFFICIAL NWS OBS.

Thunderstorm Wind in MARSHALL, IOWA
From 11-JUL-04 09:53:00 to 11-JUL-04 09:53:00 (CST)
Location: MARSHALLTOWN ARPT
Magnitude: 50 MG
Reported by: AWOS,ASOS,MESONET,ETC

Flash Flood in WAYNE, IOWA
From 11-JUL-04 17:00:00 to 11-JUL-04 22:15:00 (CST)
Location: CORYDON
Property damage: 15K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in DALLAS, IOWA
From 11-JUL-04 05:40:00 to 11-JUL-04 05:40:00 (CST)
Location: REDFIELD
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MADISON, IOWA
From 11-JUL-04 05:41:00 to 11-JUL-04 05:41:00 (CST)
Location: EARLHAM
Magnitude: 50 EG
Reported by: FIRE DEPT/RESCUE SQUAD

Hail in WARREN, IOWA
From 11-JUL-04 12:42:00 to 11-JUL-04 12:42:00 (CST)
Location: NEW VIRGINIA
Magnitude: 1.75 
Property damage: 25K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WAPELLO, IOWA
From 11-JUL-04 12:13:00 to 11-JUL-04 12:13:00 (CST)
Location: OTTUMWA
Magnitude: 57 EG
Property damage: 5K
Reported by: OFFICIAL NWS OBS.

Hail in WARREN, IOWA
From 11-JUL-04 12:39:00 to 11-JUL-04 12:39:00 (CST)
Location: NEW VIRGINIA
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in DAVIS, IOWA
From 11-JUL-04 10:30:00 to 11-JUL-04 10:30:00 (CST)
Location: BLOOMFIELD
Magnitude: 57 EG
Property damage: 25K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in DAVIS, IOWA
From 11-JUL-04 10:25:00 to 11-JUL-04 10:25:00 (CST)
Location: BLOOMFIELD
Magnitude: 50 EG
Property damage: 2K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in TAMA, IOWA
From 11-JUL-04 10:27:00 to 11-JUL-04 10:27:00 (CST)
Location: GLADBROOK
Magnitude: 50 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT