Event Summary:A squall line developed north of a stationary front across Southern Iowa into Northern Illinois in a near tropical atmosphere.  The squall line moved east and bowed out as it moved through Benton, Linn, and Jones Counties in Iowa.  Spotty severe wind was reported in the northern parts of Iowa and Johnson counties.  A bookend vorticy developed on the squall line in Jones county and moved through Jackson County Iowa and into northwest Carroll County Illinois.  Another small bowing of the squall line occurred across Whiteside County Illinois. The storms in the squall line were prolific lightning producers which caused severe damage to a house in Farmington, Iowa.

Thunderstorm Wind in MUSCATINE, IOWA
From 03-AUG-04 19:00:00 to 03-AUG-04 19:10:00 (CST)
Location: MUSCATINE MUNI ARPT
Magnitude: 50 MG
Crop damage: 2K
Reported by: AWOS,ASOS,MESONET,ETC

KMUT AWOS

Thunderstorm Wind in JACKSON, IOWA
From 03-AUG-04 19:00:00 to 03-AUG-04 19:10:00 (CST)
Location: MAQUOKETA
Magnitude: 57 EG
Property damage: 3K
Crop damage: 3K
Reported by: TRAINED SPOTTER

8 inch diameter trees snapped off

Thunderstorm Wind in JOHNSON, IOWA
From 03-AUG-04 18:11:00 to 03-AUG-04 18:16:00 (CST)
Location: IOWA CITY
Magnitude: 61 MG
Property damage: 2K
Crop damage: 3K
Reported by: GENERAL PUBLIC

Small trees down.  KIOW ASOS is the Iowa River valley and partially sheltered by higher terrain.  KIOW ASOS reported a peak wind of 43 knots (50 mph) at 1809 CST (0009 UTC).  A few sporatic reports of 40-45 knots (46-52 mph) were received west of Iowa City.

Thunderstorm Wind in JACKSON, IOWA
From 03-AUG-04 19:05:00 to 03-AUG-04 19:15:00 (CST)
Location: MAQUOKETA
Magnitude: 61 EG
Property damage: 8K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Numerous streets closed due to downed trees and power lines.  A 15 inch diameter tree down on a house.Only two severe reports were received in Jackson County.  KDVN 88D reflectivity and velocity data suggests that damage may be more widespread across the southern part of the county during 1820-1930 CST (0020-0130 UTC).  This would be consistent with the passage of the bookend vorticity as it moved across Jackson County.

Lightning in VAN BUREN, IOWA
From 03-AUG-04 23:15:00 to 03-AUG-04 23:15:00 (CST)
Location: FARMINGTON
Property damage: 20K
Reported by: TRAINED SPOTTER

Lightning strike destroyed the entire electrical system of a house and all electric appliances that were plugged into it.

Thunderstorm Wind in IOWA, IOWA
From 03-AUG-04 17:16:00 to 03-AUG-04 17:26:00 (CST)
Location: LADORA
Magnitude: 52 EG
Property damage: 3K
Crop damage: 3K
Reported by: EMERGENCY MANAGER

4 inch diameter tree limbs down with damage to the siding of some mobile homes.  Power lines also reported down.  Numerous reports of estimated 43 knot (50 mph) winds west and east of Ladora.

Thunderstorm Wind in BENTON, IOWA
From 03-AUG-04 16:54:00 to 03-AUG-04 17:40:00 (CST)
Location: COUNTYWIDE
Magnitude: 61 EG
Property damage: 150K
Crop damage: 50K
Reported by: NWS STORM SURVEY

The squall line entered northwest Benton County around 1654 CST (2254 UTC) and created a consistent path of damaging winds in an east southeast direction across the northern part of the county to the Benton/Linn County line.  Winds estimated at 52 knots (60 mph) occurred in Garrison during 1702-1712 CST, estimated 61 knots (70 mph) in Mt. Auburn 1708-1718 CST, Vinton 1713-1723 CST with a measured 58 knots (67 mph) at the sheriff department, and estimated 61 knots in Urbana 1732-1742 CST.  Considerable damage occurred at the Vinton Airport located 3 miles north of Vinton with one hangar destroyed and another severely damaged.  The damage was continuous with many corn fields flattened.  In the southern part of the county wind damage was sporatic.  Severe winds estimated at 52 knots (60 mph) occurred in Belle Plaine during 1702-1712 CST and Van Horne 1710-1720 CST.

Thunderstorm Wind in IOWA, IOWA
From 03-AUG-04 17:30:00 to 03-AUG-04 17:40:00 (CST)
Location: WILLIAMSBURG
Magnitude: 52 EG
Property damage: 3K
Crop damage: 3K
Reported by: EMERGENCY MANAGER

Trees and power lines down with several reports of estimated 43 knot (50 mph) winds west and east of Williamsburg.

Thunderstorm Wind in LINN, IOWA
From 03-AUG-04 17:23:00 to 03-AUG-04 17:40:00 (CST)
Location: CENTER PT
Magnitude: 61 EG
Property damage: 15K
Crop damage: 7K
Reported by: NWS STORM SURVEY

Squall line left Benton County between Urbana and Shellsburg and entered Linn County around 1723 CST (2323 UTC).  Center Point took a direct hit with winds estimated at 61 knots plus (70+ mph) during 1730-1740 CST.  Numerous trees and power lines were downed in the Center Point area with outbuildings destroyed or damaged and a horse trailer overturned.  No addional reports of severe winds were received after Center Point.  KDVN 88D velocity data suggests the potential for severe winds in a generally easterly path that went between Alburnett and Robins to between Waubeek and Springville to the Linn/Jones County line from 1740 to 1804 CST.  In the Cedar Rapids metropolitian area, numerous reports of estimated 43 to 48 knots (50 to 55 mph) winds were received from local TV stations with KCID ASOS reporting a peak gust of 41 knots (47 mph) at 1733 CST (2333 UTC).

Thunderstorm Wind in JONES, IOWA
From 03-AUG-04 17:55:00 to 03-AUG-04 18:50:00 (CST)
Location: COUNTYWIDE
Magnitude: 61 EG
Property damage: 20K
Crop damage: 9K
Reported by: TRAINED SPOTTER

Squall line left Linn County between Waubeek and Springville and entered Jones County around 1755 CST (2355 UTC).  Anamosa took a direct hit with winds estimated around 61 knots (70 mph) during 1758-1808 CST from a trained spotter and co-op observer.  At this point, a book end vorticy began developing across the northern part of the county.  The bookend vorticy moved in an east southeast direction from Monticello to the Jones/Jackson county line, passing north of Center Junction and Onslow.  A brief power interruption occurred at the KMXO AWOS with the arrival of the gust front during 1808-1813 CST with winds gusting to 35 knots (40 mph) prior to the outage. Power came back for 1 minute at 1814 CST before failing completely with the arrival of the bookend vorticy.  Winds estimated of at least 61 knots (70 mph) hit Monticello during 1814-1821 CST with numerous trees and power lines down.  A few homes and a car dealership on the south side of Monticello sustained roof damage and broken windows.  From Monticello to the Jones/Jackson county line, a spotter reported trees down 1.6 miles southeast of KMXO on 190th Street near Pictured Rocks State Park during 1819-1825 CST.  The local newspaper reported a dented grain bin on the Welter farm 9.0 miles east southeast of KMXO along highway 136 during 1836-1842 CST.