A large upper level low pressure system moved from northwest Kansas into south central Nebraska during the late afternoon and evening of June 20.  Temperatures and dew point temperatures ahead of the low climbed to around 90 and lower 70s respectively near and south of a warm front that extended east northeast from low pressure in southwest Nebraska.  Strong levels of wind shear combined with the high instability to produce several spiral bands of embedded supercell thunderstorms that produced fairly widespread wind damage and at least 2 tornadoes across the region.

Thunderstorm Wind in MONONA, IOWA
From 20-JUN-11 20:05:00 to 20-JUN-11 20:12:00 (CST-6)
Location: MAPLETON
Magnitude: 60.00 EG
Reported by: Emergency Manager

Thunderstorm wind gusts estimated at around 70 mph blew over a semi on Highway 141 and also blew a grain bin across the highway southwest of Mapleton.  The winds also downed trees and power lines in the Mapleton area and caused scattered building damage.

Thunderstorm Wind in MONTGOMERY, IOWA
From 20-JUN-11 20:24:00 to 20-JUN-11 20:24:00 (CST-6)
Location: HAWTHORNE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A thunderstorm wind gust was estimated at around 60 mph west of Red Oak.

Tornado in MONONA, IOWA
From 20-JUN-11 19:45:00 to 20-JUN-11 19:53:00 (CST-6)
Location: MOORHEAD
Tornado F-scale: EF1
Reported by: NWS Storm Survey

A NWS storm survey determined a tornado tracked around 7 miles southeast of the Turin area.  The tornado touched down near county roads E60 and L14 producing sporadic tree damage.  The tornado tracked north northeast hitting a farmstead along L14 uprooting trees, downing power lines and destroying a grain bin.  The tornado then moved across the Loess Hills producing varying degrees of tree damage.  After crossing county roads E54 and 277th street additional tree and farm outbuilding damage occurred.  Part of a roof of a farm house was removed near 258th Street with outbuildings also damaged in that area.  The tornado knocked down some power lines near county road L16 before lifting in that area.  The average path width was determined to be around 300 yards.

Thunderstorm Wind in HARRISON, IOWA
From 20-JUN-11 19:30:00 to 20-JUN-11 19:30:00 (CST-6)
Location: MISSOURI VLY
Magnitude: 60.00 EG
Reported by: Law Enforcement

Thunderstorm wind gusts estimated at around 70 mph downed trees and power lines in Missouri Valley.

Thunderstorm Wind in HARRISON, IOWA
From 20-JUN-11 19:30:00 to 20-JUN-11 19:30:00 (CST-6)
Location: LOGAN
Magnitude: 60.00 EG
Reported by: Law Enforcement

Thunderstorm winds estimated at around 70 mph downed trees and power lines in the Logan area.

Thunderstorm Wind in MONONA, IOWA
From 20-JUN-11 19:43:00 to 20-JUN-11 19:43:00 (CST-6)
Location: BLENCOE
Magnitude: 60.00 EG
Reported by: Emergency Manager

Thunderstorm wind gusts estimated at around 70 mph downed trees and power lines in the Blencoe area.  Some of the fallen trees also caused house damage in town.

Thunderstorm Wind in HARRISON, IOWA
From 20-JUN-11 19:45:00 to 20-JUN-11 19:45:00 (CST-6)
Location: RIVER SIOUX
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A thunderstorm wind gust estimated at around 70 mph downed at least 1 large tree northwest of Little Sioux.

Thunderstorm Wind in POTTAWATTAMIE, IOWA
From 20-JUN-11 19:25:00 to 20-JUN-11 19:35:00 (CST-6)
Location: COUNCIL BLUFFS
Magnitude: 55.00 EG
Reported by: Newspaper

Thunderstorm wind gusts estimated at over 60 mph caused tree damage across parts of Council Bluffs which in turned downed power lines knocking out power to around 4,000 people in town.