The frontal boundary that has been in place across Iowa lifted north during the day on the 18th and had become nearly stationary across northeast Iowa.  The airmass warmed into the upper 80s to low 90s, with dew points in the mid 70s to low 80s.  A significant cap was in place during the day into the evening of the 18th with 700 mb temperatures of +12 to +13 C.  Mid level temperatures cooled during the evening and overnight hours as a strong upper level trough approached the area.  The airmass remained very unstable into the early morning hours of the 19th, with CAPE in the 4000 to 5000 J/kg range and lifted indices remained in the -5 to-7 C range.  Downdraft CAPE was high at 900 to 1300 J/kg.  There was significant CAPE in the -10 to -30 C layer of the atmosphere ranging from around 700 to 900 J/kg, however the freezing level was quite high at 14,000 feet.  In addition, 1.75 to 2 inches of precipitable water was available.  Thunderstorms formed in Nebraska and moved into Iowa.  The storms were heavy precipitation storms and combined with the warm atmosphere limited the storms in hail production.  Some sub-severe hail was reported.  The storms became a forward propagating MCS and wind was the primary mode of severe weather.  Tree and power line damage was widespread with winds of 60 MPH or higher common.  The wind event took place mainly from Interstate 80 north to the U.S. 30 corridor.  In eastern Marshall County, a mesonet station recorded a 94 MPH wind gust.  Damage was widespread across eastern Marshall County into Tama County.

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 04:50:00 to 19-JUN-09 04:50:00 (CST-6)
Location: AMES
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Thunderstorm Wind in MARSHALL, IOWA
From 19-JUN-09 05:30:00 to 19-JUN-09 05:30:00 (CST-6)
Location: LURAY
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trees were reported to have blown down.

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 04:57:00 to 19-JUN-09 04:57:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 57.00 EG
Property damage: 50.00K
Crop damage: 10.00K
Reported by: Emergency Manager

Several trees down, some 2 to 4 feet in diameter.  Powerlines were down, a large tree fell and damaged a house foundation, and another large tree fell and damaged the roof of a house. Dime size hail fell too.

Thunderstorm Wind in TAMA, IOWA
From 19-JUN-09 05:52:00 to 19-JUN-09 05:52:00 (CST-6)
Location: TAMA
Magnitude: 54.00 EG
Property damage: 10.00K
Crop damage: 2.00K
Reported by: Trained Spotter

Large 12 to 14 inch diameter tree down. Six inch diameter limbs down around town.

Thunderstorm Wind in TAMA, IOWA
From 19-JUN-09 05:57:00 to 19-JUN-09 05:57:00 (CST-6)
Location: TOLEDO
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 10.00K
Reported by: Broadcast Media

Trees down in the area, and the corn was blown down.

Thunderstorm Wind in TAMA, IOWA
From 19-JUN-09 05:53:00 to 19-JUN-09 05:53:00 (CST-6)
Location: TAMA
Magnitude: 65.00 EG
Property damage: 25.00K
Crop damage: 50.00K
Reported by: Law Enforcement

Widespread tree damage was reported.

Thunderstorm Wind in CARROLL, IOWA
From 19-JUN-09 03:42:00 to 19-JUN-09 03:42:00 (CST-6)
Location: DEDHAM
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Tree limbs blown down and corn damaged.

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 04:47:00 to 19-JUN-09 04:47:00 (CST-6)
Location: SLATER
Magnitude: 57.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Trees up to 15 inch in diameter were blown down.

Hail in JASPER, IOWA
From 19-JUN-09 05:55:00 to 19-JUN-09 05:55:00 (CST-6)
Location: NEWBURG
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in AUDUBON, IOWA
From 19-JUN-09 03:29:00 to 19-JUN-09 03:29:00 (CST-6)
Location: GRAY
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Strong straight line winds caused sparking of transformers.  Large branches were down and a tree fell on a car.

Thunderstorm Wind in MARSHALL, IOWA
From 19-JUN-09 05:35:00 to 19-JUN-09 05:35:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 82.00 MG
Property damage: 25.00K
Crop damage: 100.00K
Reported by: Mesonet

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 05:07:00 to 19-JUN-09 05:07:00 (CST-6)
Location: IOWA CENTER
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 05:07:00 to 19-JUN-09 05:07:00 (CST-6)
Location: IOWA CENTER
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 6 inch or larger limbs were snapped off of trees.

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 05:04:00 to 19-JUN-09 05:04:00 (CST-6)
Location: IOWA CENTER
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 05:08:00 to 19-JUN-09 05:08:00 (CST-6)
Location: IOWA CENTER
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Two 3 foot diameter trees were uprooted and blocked the road southwest of Colo.

Thunderstorm Wind in MARSHALL, IOWA
From 19-JUN-09 05:30:00 to 19-JUN-09 05:30:00 (CST-6)
Location: LURAY
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in STORY, IOWA
From 19-JUN-09 04:57:00 to 19-JUN-09 04:57:00 (CST-6)
Location: AMES
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees and power lines blocking Riverside Road north of Ames.

Hail in CASS, IOWA
From 19-JUN-09 04:05:00 to 19-JUN-09 04:05:00 (CST-6)
Location: WIOTA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter