A strong upper level system over the southern Rockies lifted northeast across the plains causing an intense surface low pressure system and attendant warm front to lift into Nebraska.  The main warm front remained either in southern Nebraska or in Kansas, and the shear and instability associated with the system produced widespread multi-cellular convection with embedded super cell thunderstorms near and north of the front.  The more surface based super cells produced several tornadoes in southeast Nebraska and southwest Iowa, while more elevated storms in northeast Nebraska produced very large hail.  In addition, areas of very heavy rain produced isolated flash and river flooding across the area.  The severe weather came in several waves, the first one came through in the afternoon with the second a little after midnight CDT.

Flood in PAGE, IOWA
From 15-APR-12 04:00:00 to 15-APR-12 18:45:00 (CST-6)
Location: CLARINDA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Heavy rain on April 14th, around 3 to 5 inches, fell across the lower Nodaway River valley.  The rain caused flooding along the Nodaway River, with the river cresting around 23 feet, flood stage is 19 feet, during the morning of the 15th.  The flooding mainly affected lowlands along the river and caused minimal or no apparent damage.

High Wind in PAGE, IOWA
From 14-APR-12 23:00:00 to 15-APR-12 01:00:00 (CST-6)
Magnitude: 52.00 MG
Reported by: AWOS

Southwest winds of 40 to 60 mph prevailed for about 2 hours in the Shenandoah to Essex area causing isolated damage to farm outbuildings.  These southwest winds were apparently the low level jet mixing down or inflow winds to a super cell thunderstorm
at least 10 to 15 miles away to the north.  Other weaker showers and non-severe thunderstorms were 10 to 15 miles south of the region.  The Awos at Shenandoah measured a wind gust of 58 mph at 1255 am CDT and 60 mph at 155 am.

High Wind in FREMONT, IOWA
From 14-APR-12 23:00:00 to 15-APR-12 01:00:00 (CST-6)
Magnitude: 52.00 MG
Reported by: AWOS

Southwest winds of 40 to 60 mph prevailed for about 2 hours in the Shenandoah to Essex area causing isolated damage to farm outbuildings.  These southwest winds were apparently the low level jet mixing down or inflow winds to a super cell thunderstorm
at least 10 to 15 miles away to the north.  Other weaker showers and non-severe thunderstorms were 10 to 15 miles south of the region.  The Awos at Shenandoah measured a wind gust of 58 mph at 1255 am CDT and 60 mph at 155 am.

Hail in FREMONT, IOWA
From 14-APR-12 12:50:00 to 14-APR-12 12:50:00 (CST-6)
Location: RANDOLPH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MONTGOMERY, IOWA
From 14-APR-12 13:50:00 to 14-APR-12 13:50:00 (CST-6)
Location: GRANT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in MONTGOMERY, IOWA
From 14-APR-12 13:32:00 to 14-APR-12 13:32:00 (CST-6)
Location: COBURG
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Tornado in POTTAWATTAMIE, IOWA
From 14-APR-12 23:55:00 to 14-APR-12 23:57:00 (CST-6)
Location: QUICK
Tornado F-scale: EF1
Reported by: NWS Storm Survey

A tornado touched down near the entrance to the Westfair Amphitheater damaging numerous trees and outbuildings in the area.   About half the bleachers on both the west and east sides from the Westfair arena were torn from their foundation anchors and ended in a tangled pile and power poles were damaged.   The total track of the tornado was about 1 mile long and a quarter mile wide.

Thunderstorm Wind in MILLS, IOWA
From 14-APR-12 16:58:00 to 14-APR-12 16:58:00 (CST-6)
Location: EMERSON
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind gusts estimated at close to 60 mph downed a few large trees in the area.

Thunderstorm Wind in PAGE, IOWA
From 14-APR-12 17:25:00 to 14-APR-12 17:25:00 (CST-6)
Location: PAGE CENTRE
Magnitude: 52.00 EG
Reported by: Trained Spotter

Thunderstorm winds estimated at 60 mph downed several tree limbs in the area.  The winds were accompanied by hail up to quarter-size.

Thunderstorm Wind in MILLS, IOWA
From 14-APR-12 16:54:00 to 14-APR-12 16:54:00 (CST-6)
Location: HASTINGS
Magnitude: 56.00 MG
Reported by: Trained Spotter

A thunderstorm wind gust of 65 mph was measured on a home weather station.  The wind snapped a tree off just above ground level and also downed many limbs in the Hastings area.

Heavy Rain in MONTGOMERY, IOWA
From 14-APR-12 13:00:00 to 14-APR-12 16:00:00 (CST-6)
Location: RED OAK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Rainfall of 2 to 3 inches fell in about an hours time with some reports of a storm total of 5.5 inches in about 4 hours.  The heavy rain caused street flooding in the Red Oak area, especially on the east side of town and also flooded some parks and ball fields.

Thunderstorm Wind in MONTGOMERY, IOWA
From 14-APR-12 17:10:00 to 14-APR-12 17:10:00 (CST-6)
Location: RED OAK MUNI ARPT
Magnitude: 68.00 MG
Reported by: Emergency Manager

A thunderstorm wind gust of 78 mph was measured by a home weather station at 4 feet above ground level.  The strong winds caused damage to trees, power poles and a few structures in the area.

Tornado in MONONA, IOWA
From 14-APR-12 13:28:00 to 14-APR-12 13:29:00 (CST-6)
Location: GRANT CENTER
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A brief tornado touchdown was caught on film northwest of Castana.  The tornado did no apparent damage.

Tornado in FREMONT, IOWA
From 14-APR-12 16:28:00 to 14-APR-12 16:41:00 (CST-6)
Location: PERCIVAL
Tornado F-scale: EF2
Reported by: Emergency Manager

A tornado touched down near Percival, Iowa and began a 12 mile long track that went through Thurman causing extensive home, vehicle and tree damage to that town.  It was estimated that at least 70 percent of the buildings in Thurman sustained damage, including 14 homes that were destroyed.  The tornado was rated at EF2.  Only minor injuries were reported in Thurman.  However, as the tornado crossed Interstate 29, four semi trucks were overturned requiring the hospitalization of four truckers, the most serious with a punctured lung.