Thunderstorms produced large hail and damaging winds during the late afternoon and early evening of May 27th in Lyon, Sioux, and Plymouth Counties in northwest Iowa.  Heavy rain from the storms produced flash flooding in Sioux County.

Hail in PLYMOUTH, IOWA
From 27-MAY-12 16:30:00 to 27-MAY-12 16:30:00 (CST-6)
Location: AKRON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in PLYMOUTH, IOWA
From 27-MAY-12 16:35:00 to 27-MAY-12 16:35:00 (CST-6)
Location: AKRON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in SIOUX, IOWA
From 27-MAY-12 16:41:00 to 27-MAY-12 16:41:00 (CST-6)
Location: CHATSWORTH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SIOUX, IOWA
From 27-MAY-12 16:43:00 to 27-MAY-12 16:43:00 (CST-6)
Location: HAWARDEN MUNI ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SIOUX, IOWA
From 27-MAY-12 16:50:00 to 27-MAY-12 16:50:00 (CST-6)
Location: HULL
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in LYON, IOWA
From 27-MAY-12 17:20:00 to 27-MAY-12 17:20:00 (CST-6)
Location: ROCK RAPIDS
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm winds blew over two large grain bins and caused tree damage.

Thunderstorm Wind in PLYMOUTH, IOWA
From 27-MAY-12 18:15:00 to 27-MAY-12 18:15:00 (CST-6)
Location: AKRON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds caused tree damage. Several trees were blown down; some blocking Iowa Highway 12.

Thunderstorm Wind in SIOUX, IOWA
From 27-MAY-12 18:28:00 to 27-MAY-12 18:28:00 (CST-6)
Location: HAWARDEN
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorm winds caused tree damage, including several trees blown down.

Hail in LYON, IOWA
From 27-MAY-12 18:48:00 to 27-MAY-12 18:48:00 (CST-6)
Location: INWOOD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm Wind in SIOUX, IOWA
From 27-MAY-12 18:52:00 to 27-MAY-12 18:52:00 (CST-6)
Location: HULL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage, including numerous branches blown down.

Thunderstorm Wind in SIOUX, IOWA
From 27-MAY-12 19:00:00 to 27-MAY-12 19:00:00 (CST-6)
Location: BOYDEN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage.

Flash Flood in SIOUX, IOWA
From 27-MAY-12 19:02:00 to 27-MAY-12 23:00:00 (CST-6)
Location: ROCK VLY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain caused flash flooding of several roads, one of which, Main Street in Rock Valley, became impassable in the high water.

Thunderstorm Wind in LYON, IOWA
From 27-MAY-12 17:10:00 to 27-MAY-12 17:10:00 (CST-6)
Location: ALVORD
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew the roof off a business, and caused tree damage.