An upper level disturbance that lifted across the Rockies and into the Dakotas sent a cold front across eastern Nebraska and southwest Iowa during the late evening and overnight hours of June 26th and 27th.  In addition, a warm front extended ahead of the cold front near the Kansas border.  Moderate to high amounts of instability and wind shear allowed several clusters of severe thunderstorms to race across the area both ahead of and along the cold front.   Bowing segments across northeast Nebraska and west central Iowa produced areas of very strong damaging winds.  Slower moving supercell thunderstorms that developed north of the warm front produced a few large hail and strong wind reports in southwest Iowa along with very heavy rainfall.

Hail in MILLS, IOWA
From 26-JUN-11 19:41:00 to 26-JUN-11 19:41:00 (CST-6)
Location: GLENWOOD
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in FREMONT, IOWA
From 26-JUN-11 20:50:00 to 26-JUN-11 20:50:00 (CST-6)
Location: FARRAGUT
Magnitude: 55.00 EG
Reported by: Newspaper

Thunderstorm wind gusts estimated at over 60 mph downed some trees and caused some grain bin and other outbuilding damage from around Farragut to near Shenandoah.

Thunderstorm Wind in SHELBY, IOWA
From 26-JUN-11 19:28:00 to 26-JUN-11 19:35:00 (CST-6)
Location: HARLAN
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm wind gusts were measured at 58 mph by the Awos in Harlan at 835 pm CDT, while a spotter estimated a wind gust about that same magnitude in the area at 828 pm.

Thunderstorm Wind in SHELBY, IOWA
From 26-JUN-11 19:32:00 to 26-JUN-11 19:32:00 (CST-6)
Location: IRWIN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

The public estimated that thunderstorm wind gusts reached around 60 mph in the Irwin area.

Thunderstorm Wind in MONONA, IOWA
From 26-JUN-11 19:34:00 to 26-JUN-11 19:34:00 (CST-6)
Location: ONAWA
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm wind gusts estimated at over 60 mph downed trees in the Onawa area which blocked a few roads.  Torrential rain also caused some brief street flooding in town.

Thunderstorm Wind in MONONA, IOWA
From 26-JUN-11 18:45:00 to 26-JUN-11 18:45:00 (CST-6)
Location: ONAWA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind gusts were estimated at around 60 mph a little north of the Onawa area.

Thunderstorm Wind in MONONA, IOWA
From 26-JUN-11 19:35:00 to 26-JUN-11 19:35:00 (CST-6)
Location: CASTANA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind gusts were estimated at around 60 mph by a spotter about 10 miles east of Onawa.

Thunderstorm Wind in POTTAWATTAMIE, IOWA
From 26-JUN-11 19:54:00 to 26-JUN-11 19:54:00 (CST-6)
Location: OAKLAND
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind gusts were estimated at around 60 mph.

Thunderstorm Wind in MILLS, IOWA
From 26-JUN-11 20:20:00 to 26-JUN-11 20:20:00 (CST-6)
Location: HASTINGS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind gusts were estimated at around 60 mph by a spotter.

Thunderstorm Wind in HARRISON, IOWA
From 26-JUN-11 18:52:00 to 26-JUN-11 18:52:00 (CST-6)
Location: CALIFORNIA JCT
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorm wind gusts estimated at over 60 mph downed a large tree and also snapped and pushed over some corn in the area.

Thunderstorm Wind in PAGE, IOWA
From 26-JUN-11 20:52:00 to 26-JUN-11 20:52:00 (CST-6)
Location: ESSEX
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds estimated at 60 mph downed large tree limbs in the area and were also accompanied by torrential rain.

Flood in PAGE, IOWA
From 26-JUN-11 23:00:00 to 27-JUN-11 12:30:00 (CST-6)
Location: SHAMBAUGH
Flood cause: Heavy Rain
Property damage: 6.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Rainfall of 1 to 3 inches in less than a 12 hour time period brought lowland flooding along the Nodaway River in southwest Iowa.  The river near Clarinda crested around 22 feet in the morning of 6/27, flood stage is 19 feet.  The river flooded a few county roads and adjacent farm land.

Flood in FREMONT, IOWA
From 27-JUN-11 04:30:00 to 28-JUN-11 12:00:00 (CST-6)
Location: PAYNE
Flood cause: Heavy Rain
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Rainfall of 1 to 3 inches in less than a 12 hour time period brought lowland flooding along the Nishnabotna River in southwest Iowa.  The river near Hamburg crested a little over its 23 foot flood stage during the afternoon of 6/27.  The river flooded mainly farm land along the river but significant flooding from the Missouri River was ongoing in the area already.

Heavy Rain in PAGE, IOWA
From 26-JUN-11 20:00:00 to 27-JUN-11 06:00:00 (CST-6)
Location: BLANCHARD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Rainfall of a little under 2.75 inches in the Blanchard area was recorded this night.  The heavy rain in southwest Iowa helped produce flooding along the Nishnabotna and Nodaway Rivers.

Tornado in HARRISON, IOWA
From 26-JUN-11 18:55:00 to 26-JUN-11 19:00:00 (CST-6)
Location: PISGAH
Tornado F-scale: EF0
Reported by: NWS Storm Survey

A brief EF0 tornado spun up on the leading edge of a squall line about 1.2 miles southeast of Pisgah.  Trees were snapped or uprooted from the tornado.  The tornado ended about 1/2 mile east of Highway F20L and 135th St.