A warm front moved slowly north into Iowa during the overnight hours of the 28th into the 29th.  The airmass became unstable as surface temperatures warmed into the low 80s, with dewpoints around 70 along and south of the front.  CAPE rose to around 3000 J/kg with a downdraft CAPE of 900 J/kg, and CAPE in the -10 to -30 C layer of the atmosphere of 600 to 800 J/kg.  The lifted index fell to -9 C.  Considerable moisture was available with the precipitable water values around 1.7 inches.  The atmosphere was moderately sheared with 35 to 40 kts of shear available.  Thunderstorms developed rapidly around mid day and produced very heavy rainfall, as well as high winds and hail.  Most of the hail was somewhat limited in spite of the relatively low freezing level of  12,600 feet.  The LC was relatively low at 1000 meters, however there were no reports of tornadoes.  Wind and heavy rainfall was the dominant weather type.  Hail was limited to penny size up to 1.5 inches in diameter.  Several of the storms produced 60 to 70 MPH winds, downing numerous trees and power lines.  The most extensive damage was in Butler County.  Winds estimated around 80 MPH caused considerable damage to a containment build and significant structural damage to 18 houses in the town of Greene.  Damage in town was around $500,000.  A band of 2 to 4 inches of rainfall was observed from southwest through central into northeast Iowa.  This caused flash flooding as the rain fell on already saturated soil.  There were numerous roads under water from the flood waters.  In the Waterloo area, the water was deep enough to submerge cars and cause many motorists to stall out and become stranded buy the flood waters.  In the Hudson areas of Black Hawk County, flooding in town occurred as the levy partially failed on the river. Officials in Tama County reported that a bridge was washed out, at a cost of $75,000, and at least $150,000 in damage to secondary roads.  In Grundy County, initial estimates of damage to county secondary roads was at least $170,000.  As of the 29th of May, Governor Terry Branstad declared 15 Iowa counties disaster areas due to the storms and flooding.  They included Buena Vista, Cherokee, Butler, Floyd, Grundy, Johnson, Iowa, Jasper, Marshall, Mitchell, Plymouth, Poweshiek, Sioux, Tama, Wapello, and Wright.

Hail in GUTHRIE, IOWA
From 29-MAY-13 10:00:00 to 29-MAY-13 10:00:00 (CST-6)
Location: GUTHRIE CENTER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in GREENE, IOWA
From 29-MAY-13 10:29:00 to 29-MAY-13 10:32:00 (CST-6)
Location: RIPPEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail and smaller lasted 3 minutes.

Hail in BOONE, IOWA
From 29-MAY-13 10:39:00 to 29-MAY-13 10:40:00 (CST-6)
Location: LUTHER
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in BOONE, IOWA
From 29-MAY-13 10:41:00 to 29-MAY-13 10:41:00 (CST-6)
Location: OGDEN
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Emergency Manager

Hail covered the ground.

Hail in BOONE, IOWA
From 29-MAY-13 10:59:00 to 29-MAY-13 10:59:00 (CST-6)
Location: OGDEN
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Hail in BOONE, IOWA
From 29-MAY-13 11:16:00 to 29-MAY-13 11:16:00 (CST-6)
Location: OGDEN
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 29-MAY-13 13:57:00 to 29-MAY-13 13:57:00 (CST-6)
Location: ANKENY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STORY, IOWA
From 29-MAY-13 14:17:00 to 29-MAY-13 14:17:00 (CST-6)
Location: IOWA CENTER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in JASPER, IOWA
From 29-MAY-13 14:38:00 to 29-MAY-13 14:38:00 (CST-6)
Location: VALERIA
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Hail in MARSHALL, IOWA
From 29-MAY-13 15:03:00 to 29-MAY-13 15:03:00 (CST-6)
Location: GILMAN
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 29-MAY-13 15:39:00 to 29-MAY-13 15:39:00 (CST-6)
Location: WATERLOO
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in MARSHALL, IOWA
From 29-MAY-13 15:03:00 to 29-MAY-13 15:03:00 (CST-6)
Location: GILMAN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter estimated 60 MPH winds.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-13 13:45:00 to 29-MAY-13 13:45:00 (CST-6)
Location: RIDER
Magnitude: 55.00 MG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in POLK, IOWA
From 29-MAY-13 14:12:00 to 29-MAY-13 14:12:00 (CST-6)
Location: BONDURANT
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public estimated winds of 60 MPH.

Thunderstorm Wind in JASPER, IOWA
From 29-MAY-13 14:45:00 to 29-MAY-13 14:45:00 (CST-6)
Location: MINGO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Estimated winds of 60 MPH along with pea size hail.

Thunderstorm Wind in MARSHALL, IOWA
From 29-MAY-13 14:53:00 to 29-MAY-13 14:53:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 59.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in HARDIN, IOWA
From 29-MAY-13 12:25:00 to 29-MAY-13 12:25:00 (CST-6)
Location: STEAMBOAT ROCK
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in BUTLER, IOWA
From 29-MAY-13 13:01:00 to 29-MAY-13 13:01:00 (CST-6)
Location: GREENE
Magnitude: 70.00 EG
Property damage: 600.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Large steel outbuilding was destroyed.  Eighteen houses sustained structural damage.

Thunderstorm Wind in BLACK HAWK, IOWA
From 29-MAY-13 15:38:00 to 29-MAY-13 15:38:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power lines were reported down.

Thunderstorm Wind in BLACK HAWK, IOWA
From 29-MAY-13 15:38:00 to 29-MAY-13 15:38:00 (CST-6)
Location: WATERLOO
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees were reported down from high wind.

Hail in BLACK HAWK, IOWA
From 29-MAY-13 15:34:00 to 29-MAY-13 15:34:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash Flood in HARDIN, IOWA
From 29-MAY-13 15:26:00 to 29-MAY-13 20:30:00 (CST-6)
Location: ELDORA
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over many county roads in the east part of the county.

Flash Flood in BLACK HAWK, IOWA
From 29-MAY-13 15:49:00 to 29-MAY-13 21:30:00 (CST-6)
Location: CASTLE HILL
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Social Media

University Ave near Town House Tenderloins flooded.  At least one care was submerged.

Thunderstorm Wind in FRANKLIN, IOWA
From 29-MAY-13 14:06:00 to 29-MAY-13 14:06:00 (CST-6)
Location: HANSELL
Magnitude: 52.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Winds from a decaying thunderstorms blew a tree onto a house.  A porch was also damaged by the high winds.

Flash Flood in STORY, IOWA
From 29-MAY-13 17:04:00 to 29-MAY-13 20:30:00 (CST-6)
Location: NEVADA
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Indian Creek is reportedly out of its banks in Nevada.

Flash Flood in BREMER, IOWA
From 29-MAY-13 16:00:00 to 29-MAY-13 21:30:00 (CST-6)
Location: WAVERLY
Flood cause: Heavy Rain
Property damage: 300.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Several roads across the county have water over them from small creeks and streams.  Flooding reported in the cities.

Flash Flood in STORY, IOWA
From 29-MAY-13 15:30:00 to 29-MAY-13 20:30:00 (CST-6)
Location: COLO
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Public

Water over the road near Hickory Grove Park on 670th Ave and 650th near 260th St.

Heavy Rain in STORY, IOWA
From 29-MAY-13 15:30:00 to 29-MAY-13 17:00:00 (CST-6)
Location: IOWA CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reports 3.1 inches of rain fell in an hour and a half ending at 1700 CST.  Several reports of roads washed out in the area.

Flash Flood in GREENE, IOWA
From 29-MAY-13 16:31:00 to 29-MAY-13 19:00:00 (CST-6)
Location: JEFFERSON
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Water over the road at K Ave and 250th caused by flash flooding.

Hail in MADISON, IOWA
From 29-MAY-13 13:29:00 to 29-MAY-13 13:29:00 (CST-6)
Location: EARLHAM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in MARSHALL, IOWA
From 29-MAY-13 15:30:00 to 29-MAY-13 15:30:00 (CST-6)
Location: DUNBAR
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in MARSHALL, IOWA
From 29-MAY-13 15:50:00 to 29-MAY-13 15:50:00 (CST-6)
Location: GILMAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in MARSHALL, IOWA
From 29-MAY-13 15:00:00 to 29-MAY-13 15:00:00 (CST-6)
Location: GILMAN ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Thunderstorm Wind in POLK, IOWA
From 29-MAY-13 14:00:00 to 29-MAY-13 14:00:00 (CST-6)
Location: POLK CITY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

Hail in GREENE, IOWA
From 29-MAY-13 10:24:00 to 29-MAY-13 10:29:00 (CST-6)
Location: RIPPEY
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Nickel to quarter size hail was reported for several minutes.

Hail in STORY, IOWA
From 29-MAY-13 12:00:00 to 29-MAY-13 12:05:00 (CST-6)
Location: ROLAND
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in STORY, IOWA
From 29-MAY-13 11:57:00 to 29-MAY-13 11:57:00 (CST-6)
Location: ROLAND
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Thunderstorm Wind in BUTLER, IOWA
From 29-MAY-13 13:01:00 to 29-MAY-13 13:01:00 (CST-6)
Location: WILMAR
Magnitude: 61.00 EG
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Small car and tractor blown off highway.  Many large trees down on houses.  Numerous trees up to 4 feet in diameter and power lines down in the city of Greene with the entire city without power.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-13 13:36:00 to 29-MAY-13 13:41:00 (CST-6)
Location: URBANDALE
Magnitude: 55.00 MG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured wind for 5 minutes.

Flash Flood in DALLAS, IOWA
From 29-MAY-13 14:45:00 to 29-MAY-13 20:00:00 (CST-6)
Location: SHULER MINE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: County Official

A section of a gravel road was under water.

Flash Flood in POLK, IOWA
From 29-MAY-13 15:10:00 to 29-MAY-13 19:00:00 (CST-6)
Location: RIDER
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flooding occurring at Cutty's Campground.  People were unable to enter or exit the campground.

Flash Flood in STORY, IOWA
From 29-MAY-13 15:24:00 to 29-MAY-13 20:30:00 (CST-6)
Location: ZEARING
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Many roads in the east part of the county experiencing flooding.  Water over parts of Highway 65 in Zearing.

Flash Flood in GRUNDY, IOWA
From 29-MAY-13 15:29:00 to 29-MAY-13 19:30:00 (CST-6)
Location: HOLLAND
Flood cause: Heavy Rain
Property damage: 450.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Many county roads closed due to flooding.

Thunderstorm Wind in BLACK HAWK, IOWA
From 29-MAY-13 15:34:00 to 29-MAY-13 15:34:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 56.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Many trees were down in the residential areas of the Cedar Falls and Waterloo areas.  Dime to nickel size hail was also reported.

Thunderstorm Wind in BUTLER, IOWA
From 29-MAY-13 12:55:00 to 29-MAY-13 12:55:00 (CST-6)
Location: AREDALE
Magnitude: 61.00 EG
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Public

Significant roof damage to a containment building.

Thunderstorm Wind in BLACK HAWK, IOWA
From 29-MAY-13 15:55:00 to 29-MAY-13 15:55:00 (CST-6)
Location: DUNKERTON DAVIS ARPT
Magnitude: 50.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured by roof top anemometer at the intersection of Highway 281 and Gresham Rd.

Flash Flood in BLACK HAWK, IOWA
From 29-MAY-13 16:04:00 to 29-MAY-13 21:30:00 (CST-6)
Location: WATERLOO
Flood cause: Heavy Rain
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A car stalled in flash flood waters near the Grout Museum.

Flash Flood in BLACK HAWK, IOWA
From 29-MAY-13 16:11:00 to 29-MAY-13 21:30:00 (CST-6)
Location: EVANSDALE
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding at Black Hawk and Ansborough Ave.  Southbound U.S. 218 at Washington and Mullan Ave flooded.

Flash Flood in TAMA, IOWA
From 29-MAY-13 17:16:00 to 29-MAY-13 21:30:00 (CST-6)
Location: TRAER MUNI ARPT
Flood cause: Heavy Rain
Property damage: 450.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Several roads were covered  with water across the county.

Flash Flood in POLK, IOWA
From 29-MAY-13 17:50:00 to 29-MAY-13 19:00:00 (CST-6)
Location: ANKENY
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Social Media

Water from the field was flowing across NW 30th St west of State Street in Ankeny.

Flash Flood in STORY, IOWA
From 29-MAY-13 18:24:00 to 29-MAY-13 20:30:00 (CST-6)
Location: ZEARING
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Minerva Creek in Zearing out of its banks and flooding parts of town.

Flood in GRUNDY, IOWA
From 29-MAY-13 20:51:00 to 30-MAY-13 01:45:00 (CST-6)
Location: MORRISON
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Still reporting major flooding throughout the county with many county roads and some city streets closed due to flooding.  Highway 14 south of Grundy Center is closed as is the Highway 20 exit at Wellsburg.

Hail in BLACK HAWK, IOWA
From 29-MAY-13 15:30:00 to 29-MAY-13 15:30:00 (CST-6)
Location: WATERLOO
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Social Media

Flood in BLACK HAWK, IOWA
From 30-MAY-13 07:37:00 to 30-MAY-13 17:45:00 (CST-6)
Location: HUDSON
Flood cause: Dam / Levee Break
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flooding of areas streams and creeks resulted in flooding in Hudson and Dunkerton with volunteer evacuations underway.  Some roads remain flooded.

Flash Flood in MARSHALL, IOWA
From 29-MAY-13 15:22:00 to 29-MAY-13 20:30:00 (CST-6)
Location: LURAY
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Lots of street flooding in town.  Many roads in Marshall County under water.

Flash Flood in STORY, IOWA
From 29-MAY-13 17:00:00 to 29-MAY-13 20:30:00 (CST-6)
Location: IOWA CENTER
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several roads were washed out by flash flooding.