Thunderstorm winds produced large hail, damaging winds, and three brief tornadoes across northwest Iowa during the afternoon and evening of May 4th. Most of the severe weather was during the middle afternoon.

Thunderstorm Wind in SIOUX, IOWA
From 04-MAY-12 14:12:00 to 04-MAY-12 14:12:00 (CST-6)
Location: SIOUX CENTER
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds damaged a roof, and caused tree damage, including some trees uprooted.

Thunderstorm Wind in SIOUX, IOWA
From 04-MAY-12 14:20:00 to 04-MAY-12 14:20:00 (CST-6)
Location: ORANGE CITY ARPT
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Tornado in SIOUX, IOWA
From 04-MAY-12 14:22:00 to 04-MAY-12 14:23:00 (CST-6)
Location: ORANGE CITY
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A brief tornado caused no reported damage.

Thunderstorm Wind in SIOUX, IOWA
From 04-MAY-12 14:23:00 to 04-MAY-12 14:23:00 (CST-6)
Location: ORANGE CITY ARPT
Magnitude: 69.00 MG
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm winds caused an unknown amount of tree and power line damage.

Thunderstorm Wind in PLYMOUTH, IOWA
From 04-MAY-12 14:30:00 to 04-MAY-12 14:30:00 (CST-6)
Location: BRUNSVILLE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Estimated 60 mph wind gusts were accompanied by large hail.

Hail in PLYMOUTH, IOWA
From 04-MAY-12 14:30:00 to 04-MAY-12 14:30:00 (CST-6)
Location: BRUNSVILLE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large hail was accompanied by 60 mph wind gusts.

Thunderstorm Wind in O'BRIEN, IOWA
From 04-MAY-12 14:40:00 to 04-MAY-12 14:40:00 (CST-6)
Location: PHILBY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

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

Thunderstorm Wind in PLYMOUTH, IOWA
From 04-MAY-12 14:40:00 to 04-MAY-12 14:40:00 (CST-6)
Location: LE MARS MUNI ARPT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage, including branches blown down.

Thunderstorm Wind in O'BRIEN, IOWA
From 04-MAY-12 14:45:00 to 04-MAY-12 14:45:00 (CST-6)
Location: SHELDON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

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

Thunderstorm Wind in SIOUX, IOWA
From 04-MAY-12 14:46:00 to 04-MAY-12 14:46:00 (CST-6)
Location: HOSPERS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage, including branches blown down. The winds were accompanied by small hail.

Thunderstorm Wind in PLYMOUTH, IOWA
From 04-MAY-12 14:47:00 to 04-MAY-12 14:47:00 (CST-6)
Location: LE MARS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

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

Thunderstorm Wind in DICKINSON, IOWA
From 04-MAY-12 15:10:00 to 04-MAY-12 15:10:00 (CST-6)
Location: MONTGOMERY
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in CLAY, IOWA
From 04-MAY-12 15:10:00 to 04-MAY-12 15:10:00 (CST-6)
Location: EVERLY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage, including  branches blown down.

Thunderstorm Wind in DICKINSON, IOWA
From 04-MAY-12 15:24:00 to 04-MAY-12 15:24:00 (CST-6)
Location: FULLER FLD ARPT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

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

Thunderstorm Wind in CLAY, IOWA
From 04-MAY-12 15:30:00 to 04-MAY-12 15:30:00 (CST-6)
Location: DICKENS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds caused tree damage.

Hail in SIOUX, IOWA
From 04-MAY-12 20:36:00 to 04-MAY-12 20:36:00 (CST-6)
Location: ROCK VLY
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SIOUX, IOWA
From 04-MAY-12 20:43:00 to 04-MAY-12 20:43:00 (CST-6)
Location: PERKINS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SIOUX, IOWA
From 04-MAY-12 20:45:00 to 04-MAY-12 20:45:00 (CST-6)
Location: PERKINS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in SIOUX, IOWA
From 04-MAY-12 14:06:00 to 04-MAY-12 14:08:00 (CST-6)
Location: HAWARDEN
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large hail was accompanied by estimated 45 mph wind gusts.

Tornado in O'BRIEN, IOWA
From 04-MAY-12 14:50:00 to 04-MAY-12 14:51:00 (CST-6)
Location: PRIMGHAR
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A brief tornado caused no reported damage.

Thunderstorm Wind in CHEROKEE, IOWA
From 04-MAY-12 15:05:00 to 04-MAY-12 15:05:00 (CST-6)
Location: CLEGHORN
Magnitude: 52.00 EG
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds caused tree and building damage.

Thunderstorm Wind in O'BRIEN, IOWA
From 04-MAY-12 15:15:00 to 04-MAY-12 15:15:00 (CST-6)
Location: HARTLEY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

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

Tornado in SIOUX, IOWA
From 04-MAY-12 14:15:00 to 04-MAY-12 14:16:00 (CST-6)
Location: SIOUX CENTER
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A brief tornado caused no reported damage.

Thunderstorm Wind in CLAY, IOWA
From 04-MAY-12 15:22:00 to 04-MAY-12 15:24:00 (CST-6)
Location: (3SE)SPENCER MUNI AR
Magnitude: 60.00 MG
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm winds caused widespread tree damage, including several trees blown down. The winds also caused an unknown amount of structure damage.