Thunderstorms developed during the afternoon in Central Iowa along an old stationary front in hot and humid conditions.  The thunderstorms moved into Eastern Iowa and became severe.  Winds of 50 mph were common along the main gust front breaking many small limbs from trees.  The storms reached maximum intensity between 1700 and 1800 CST in Eastern Iowa where a downburst caused severe damage to the NWS office in Davenport, Iowa.  Once the storms crossed the Mississippi River, they quickly lost strength due to the setting sun and moving away from the better moisture convergence along the old front.

Thunderstorm Wind in LINN, IOWA
From 20-AUG-03 16:13:00 to 20-AUG-03 16:18:00 (CST)
Location: CENTER PT
Magnitude: 52 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Trees down

Thunderstorm Wind in DUBUQUE, IOWA
From 20-AUG-03 17:25:00 to 20-AUG-03 17:30:00 (CST)
Location: PEOSTA
Magnitude: 52 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Tree limbs down

Thunderstorm Wind in BENTON, IOWA
From 20-AUG-03 15:53:00 to 20-AUG-03 15:58:00 (CST)
Location: WATKINS
Magnitude: 61 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Event occurred in Norway, Iowa

Thunderstorm Wind in BENTON, IOWA
From 20-AUG-03 16:00:00 to 20-AUG-03 16:05:00 (CST)
Location: VINTON
Magnitude: 50 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in JOHNSON, IOWA
From 20-AUG-03 15:53:00 to 20-AUG-03 15:56:00 (CST)
Location: NORTH LIBERTY
Magnitude: 50 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Occurred with the gust front; 18 inch diameter trees down

Hail in SCOTT, IOWA
From 20-AUG-03 17:49:00 to 20-AUG-03 17:53:00 (CST)
Location: BLUE GRASS
Magnitude: 1.25 
Property damage: 10K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Hail in SCOTT, IOWA
From 20-AUG-03 17:55:00 to 20-AUG-03 17:58:00 (CST)
Location: BUFFALO
Magnitude: 1.75 
Property damage: 10K
Crop damage: 4K
Reported by: TRAINED SPOTTER

Hail in SCOTT, IOWA
From 20-AUG-03 18:01:00 to 20-AUG-03 18:03:00 (CST)
Location: DAVENPORT ARPT
Magnitude: 0.88 
Property damage: 2K
Reported by: OFFICIAL NWS OBS.

Hail size estimated by NWS personnel due to dangerous winds.

Thunderstorm Wind in DUBUQUE, IOWA
From 20-AUG-03 17:20:00 to 20-AUG-03 17:28:00 (CST)
Location: FARLEY
Magnitude: 52 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Trees down

Thunderstorm Wind in DUBUQUE, IOWA
From 20-AUG-03 17:22:00 to 20-AUG-03 17:28:00 (CST)
Location: EPWORTH
Magnitude: 52 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Trees down

Thunderstorm Wind in JACKSON, IOWA
From 20-AUG-03 17:00:00 to 20-AUG-03 17:15:00 (CST)
Location: MAQUOKETA
Magnitude: 55 EG
Property damage: 15K
Reported by: LAW ENFORCEMENT

Trees and Power lines down.

Thunderstorm Wind in KEOKUK, IOWA
From 20-AUG-03 15:43:00 to 20-AUG-03 15:50:00 (CST)
Location: SIGOURNEY
Magnitude: 55 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Large branches down

Thunderstorm Wind in SCOTT, IOWA
From 20-AUG-03 17:57:00 to 20-AUG-03 18:09:00 (CST)
Location: DAVENPORT ARPT
Magnitude: 65 EG
Property damage: 3K
Reported by: NWS EMPLOYEE(OFF DUTY)

Large tree down on farm along North Division Street

Thunderstorm Wind in SCOTT, IOWA
From 20-AUG-03 17:57:00 to 20-AUG-03 18:09:00 (CST)
Location: DAVENPORT ARPT
Magnitude: 65 EG
Property damage: 10K
Reported by: NWS EMPLOYEE(OFF DUTY)

Power lines down.

Thunderstorm Wind in LINN, IOWA
From 20-AUG-03 16:17:00 to 20-AUG-03 16:22:00 (CST)
Location: LAFAYETTE
Magnitude: 52 EG
Property damage: 3K
Reported by: EMERGENCY MANAGER

Trees down.

Thunderstorm Wind in JACKSON, IOWA
From 20-AUG-03 17:15:00 to 20-AUG-03 17:25:00 (CST)
Location: MAQUOKETA
Magnitude: 61 EG
Property damage: 2K
Crop damage: 25K
Reported by: OFFICIAL NWS OBS.

Corn flattened with tree limbs down

Thunderstorm Wind in SCOTT, IOWA
From 20-AUG-03 18:00:00 to 20-AUG-03 18:10:00 (CST)
Location: MT JOY
Magnitude: 70 EG
Property damage: 8K
Reported by: TRAINED SPOTTER

At intersection of Scott County Park Road and 215th Street.  A metal shed was flattened along with a garage door blown in.  Limbs were found 40 to 50 feet away from the parent tree and a flag pole was 5 degrees off vertical.

Thunderstorm Wind in SCOTT, IOWA
From 20-AUG-03 17:58:00 to 20-AUG-03 18:10:00 (CST)
Location: DAVENPORT ARPT
Magnitude: 80 EG
Property damage: 55K
Reported by: OFFICIAL NWS OBS.

Winds of 50 knots began at 1758 CST according to DVN ASOS.  At 1800 CST measured gusts of 58 knots (67 mph) were recorded and at 1801 CST, DVN ASOS measured a gust of 67 knots (77 mph). Before the ASOS could update for 1802 CST a power failure occurred at the ASOS site. NWS personnel at WFO DVN estimated winds of at least 80 knots (92 mph) lasting for 2 or 3 minutes (Review of archived data indicated the DVN 88D measured winds of 80+ knots about 3 miles east of the office at 200 AGL).  During this time about one third of the outer roof of the NWS building was peeled off (the roof is designed to withstand 90 mph winds).  Only the air conditioning units on the roof prevented the peeling from going the entire length of the building.  With the outer roof gone, water fell into the operations area necessitating a shut down of all equipment and implementation of service backup by WFO Des Moines.  The only damage sustained to equipment inside the building was the phone system, 2 monitors,  and 2 computer mice. Downed power lines were noted in the 9000 block of Harrison Street from the office along with numerous trees down.

Thunderstorm Wind in SCOTT, IOWA
From 20-AUG-03 18:00:00 to 20-AUG-03 18:10:00 (CST)
Location: DAVENPORT ARPT
Magnitude: 70 EG
Property damage: 15K
Reported by: NWS EMPLOYEE(OFF DUTY)

Large Interstate highway sign down on U.S. 61 just north of the I-80 & U.S. 61 interchange.

Thunderstorm Wind in JACKSON, IOWA
From 20-AUG-03 17:24:00 to 20-AUG-03 17:34:00 (CST)
Location: MAQUOKETA
Magnitude: 61 EG
Property damage: 2K
Reported by: OFFICIAL NWS OBS.

Cherry & apple trees down

Thunderstorm Wind in JACKSON, IOWA
From 20-AUG-03 17:35:00 to 20-AUG-03 17:43:00 (CST)
Location: FULTON
Magnitude: 55 EG
Property damage: 6K
Reported by: OFFICIAL NWS OBS.

Tree down on house

Thunderstorm Wind in IOWA, IOWA
From 20-AUG-03 15:30:00 to 20-AUG-03 15:36:00 (CST)
Location: LADORA
Magnitude: 52 EG
Property damage: 3K
Reported by: LAW ENFORCEMENT

Signs and branches down.

Thunderstorm Wind in JACKSON, IOWA
From 20-AUG-03 17:30:00 to 20-AUG-03 17:45:00 (CST)
Location: PRESTON
Magnitude: 61 EG
Property damage: 10K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Trees down;lasted 15 minutes

Thunderstorm Wind in JONES, IOWA
From 20-AUG-03 16:55:00 to 20-AUG-03 17:05:00 (CST)
Location: WYOMING
Magnitude: 61 EG
Property damage: 50K
Crop damage: 5K
Reported by: NEWSPAPER

Numerous trees down on houses & vehicles.  Small Outbuilding blown over.

Thunderstorm Wind in MUSCATINE, IOWA
From 20-AUG-03 17:00:00 to 20-AUG-03 17:08:00 (CST)
Location: MUSCATINE
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Jct of Iowa 38 & 155th Street

Thunderstorm Wind in MUSCATINE, IOWA
From 20-AUG-03 16:44:00 to 20-AUG-03 16:54:00 (CST)
Location: ATALISSA
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Hail in JONES, IOWA
From 20-AUG-03 16:50:00 to 20-AUG-03 16:53:00 (CST)
Location: ANAMOSA
Magnitude: 0.88 
Property damage: 2K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Occurred near Amber, Iowa

Thunderstorm Wind in IOWA, IOWA
From 20-AUG-03 15:20:00 to 20-AUG-03 15:25:00 (CST)
Location: VICTOR
Magnitude: 52 EG
Property damage: 3K
Reported by: LAW ENFORCEMENT

Signs and branches down

Thunderstorm Wind in KEOKUK, IOWA
From 20-AUG-03 15:30:00 to 20-AUG-03 15:35:00 (CST)
Location: WHAT CHEER
Magnitude: 52 EG
Property damage: 6K
Reported by: EMERGENCY MANAGER

Also reported by spotters; limbs down and tin roof off an outbuilding

Thunderstorm Wind in KEOKUK, IOWA
From 20-AUG-03 15:35:00 to 20-AUG-03 15:45:00 (CST)
Location: DELTA
Magnitude: 60 EG
Property damage: 6K
Reported by: TRAINED SPOTTER

Tree damaged; antenna off roof

Thunderstorm Wind in KEOKUK, IOWA
From 20-AUG-03 15:45:00 to 20-AUG-03 15:52:00 (CST)
Location: HAYESVILLE
Magnitude: 70 EG
Property damage: 30K
Crop damage: 8K
Reported by: EMERGENCY MANAGER

Also 1 West of Hayesville; heavy damage to a grain silo with power poles snapped in half.