The frontal boundary from the previous night lifted north as a warm front as low pressure over Kansas pushed northeast into Iowa.  The low eventually tracked from southwest Iowa in the afternoon to east central Iowa by early evening.  To the southeast of the front, temperatures warmed into the upper 70s to mid 80s, with dew point temperatures in the upper 50s to mid 60s.  The atmosphere became quite unstable with lifted indices falling to -5 to -8 Celsius and CAPE rising to 2000-3000 J/kg.  The situation was very dynamic with a synoptic scale upper level trough to the west and broad southwest flow over the central U.S.  The jet at 300 mb was around 100 kts with 500 mb winds southwest at 75+ kts.  This aided in producing deep layer shear of 75 to 100 kts over southeast Iowa by late afternoon.  Ample inflow was present with moisture transport at the 850 mb level produced by a 35 to 40 kt flow.  This increased precipitable water values to between 1 and 1.2 inches.  Thunderstorms fired along the frontal boundary during the mid to late afternoon as the front became a cold front.  With 300-400 J/kg of CAPE in the -10 to -30 layer of the atmosphere, and 700-1000 J/kg of downdraft CAPE available, the atmosphere was loaded for the production of wind and hail.  In addition, the freezing level was a relatively low 12,000 feet.  The line of thunderstorms that formed ahead of the advancing cold front became severe quickly, producing large hail.  Much of the hail was in the 1 to 1.5 inch diameter range, however there were several reports of golf ball to tennis ball size hail.  The largest hail was over northeast Iowa with golf ball size reported in Grundy County, and tennis ball size from the northwest edge of Waterloo toward Cedar Falls in Black Hawk County.  Also in Black Hawk County, a few stones were measured to 3.5 inches in diameter in Cedar Falls.  As the system unfolded, the storms began to produce high winds.  Wind gusts of 75 to 100 MPH occurred with the stronger storms.  Multiple homes had siding damage due to hail blown through the siding, and windows were knocked out in Marion County east of Monroe.  High winds snapped power poles in Jasper and Poweshiek Counties.  A camper was blown off of Interstate 80 at mile post 178, resulting in a multiple car accident.  In Poweshiek County, cars were blown off of the road and flipped, power poles snapped, and roofs were taken off of houses near Grinnell.  Power was knocked out to several thousand customers in the Grinnell area.  Six members of the Grinnell College track team were caught in the storm and sustained injuries from the hail.  They were bruised, taken to the hospital, treated and released.  Officials in the city of Grinnell estimated damage due to the high winds from this storm at $10,000,000.

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:09:00 to 06-APR-10 16:09:00 (CST-6)
Location: WATERLOO
Magnitude: 1.75 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in JASPER, IOWA
From 06-APR-10 16:55:00 to 06-APR-10 16:55:00 (CST-6)
Location: TURNER
Magnitude: 83.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Amateur Radio

There were several power poles snapped along T38.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 16:56:00 to 06-APR-10 16:56:00 (CST-6)
Location: GRINNELL
Magnitude: 78.00 EG
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Damage was caused to several homes in Grinnell.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 17:01:00 to 06-APR-10 17:01:00 (CST-6)
Location: GRINNELL
Magnitude: 78.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Two power poles were blown down and damage was reported to small buildings.

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:09:00 to 06-APR-10 16:09:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 3.50 
Property damage: 1.00M
Crop damage: 0.00K
Reported by: Broadcast Media

The ground was covered by 1 to 3.5 inch diameter hail.

Hail in JASPER, IOWA
From 06-APR-10 17:07:00 to 06-APR-10 17:07:00 (CST-6)
Location: MONROE
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in WARREN, IOWA
From 06-APR-10 17:22:00 to 06-APR-10 17:22:00 (CST-6)
Location: PALMYRA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in JASPER, IOWA
From 06-APR-10 17:44:00 to 06-APR-10 17:44:00 (CST-6)
Location: MONROE
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in JASPER, IOWA
From 06-APR-10 17:44:00 to 06-APR-10 17:44:00 (CST-6)
Location: MONROE
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in MARION, IOWA
From 06-APR-10 16:30:00 to 06-APR-10 16:30:00 (CST-6)
Location: OTLEY
Magnitude: 83.00 EG
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Multiple homes with hail damaged siding, windows knocked out, garage with two walls blown out, and a machine shed roof was blown off.  Two large trees were also twisted.

Thunderstorm Wind in JASPER, IOWA
From 06-APR-10 16:46:00 to 06-APR-10 16:46:00 (CST-6)
Location: SULLY
Magnitude: 58.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in JASPER, IOWA
From 06-APR-10 16:57:00 to 06-APR-10 16:57:00 (CST-6)
Location: TURNER
Magnitude: 70.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew a camper off the road at mile post 178, causing a multiple vehicle accident.

Thunderstorm Wind in JASPER, IOWA
From 06-APR-10 16:47:00 to 06-APR-10 16:47:00 (CST-6)
Location: SULLY
Magnitude: 83.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous power power outages were reported along with three power poles down near Highway F62.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 17:02:00 to 06-APR-10 17:02:00 (CST-6)
Location: GRINNELL
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Sheet metal was blown down and there was street sign damage.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 17:05:00 to 06-APR-10 17:05:00 (CST-6)
Location: BROOKLYN
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Tree damage was reported with winds estimated near 75 MPH.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 17:00:00 to 06-APR-10 17:00:00 (CST-6)
Location: GRINNELL
Magnitude: 70.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Two barns were blown down just west of Grinnell.

Thunderstorm Wind in POWESHIEK, IOWA
From 06-APR-10 16:56:00 to 06-APR-10 16:56:00 (CST-6)
Location: GRINNELL
Magnitude: 91.00 EG
Property damage: 3.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

On the north edge of Grinnell, cars were reported off the road and flipped.  Power lines were down and roofs were blown off homes.

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:01:00 to 06-APR-10 16:01:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:08:00 to 06-APR-10 16:08:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 2.50 
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:05:00 to 06-APR-10 16:05:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 2.00 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Funnel Cloud in POWESHIEK, IOWA
From 06-APR-10 17:06:00 to 06-APR-10 17:06:00 (CST-6)
Location: MALCOLM
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The funnel cloud was less then half way to the ground.

Hail in GRUNDY, IOWA
From 06-APR-10 15:50:00 to 06-APR-10 15:50:00 (CST-6)
Location: DIKE
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 15:58:00 to 06-APR-10 15:58:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 0.88 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 15:54:00 to 06-APR-10 15:54:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 15:59:00 to 06-APR-10 15:59:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 15:58:00 to 06-APR-10 15:58:00 (CST-6)
Location: WATERLOO
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:02:00 to 06-APR-10 16:02:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.50 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in GRUNDY, IOWA
From 06-APR-10 15:55:00 to 06-APR-10 15:55:00 (CST-6)
Location: DIKE
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:09:00 to 06-APR-10 16:09:00 (CST-6)
Location: WATERLOO
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:04:00 to 06-APR-10 16:04:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 2.00 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:05:00 to 06-APR-10 16:05:00 (CST-6)
Location: CEDAR CITY
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:08:00 to 06-APR-10 16:08:00 (CST-6)
Location: (ALO)WATERLOO MUNI A
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in BREMER, IOWA
From 06-APR-10 16:14:00 to 06-APR-10 16:14:00 (CST-6)
Location: DENVER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:10:00 to 06-APR-10 16:10:00 (CST-6)
Location: (ALO)WATERLOO MUNI A
Magnitude: 2.50 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Tennis ball size hail just south of the Waterloo Airport, reported by KWWL.

Hail in BREMER, IOWA
From 06-APR-10 16:22:00 to 06-APR-10 16:22:00 (CST-6)
Location: READLYN
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:05:00 to 06-APR-10 16:05:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MARION, IOWA
From 06-APR-10 16:24:00 to 06-APR-10 16:24:00 (CST-6)
Location: KNOXVILLE
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Hail was reported on the northwest edge of Knoxville.

Hail in BLACK HAWK, IOWA
From 06-APR-10 16:10:00 to 06-APR-10 16:10:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 1.75 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail was reported at the intersection of 6th and Main.

Hail in MARION, IOWA
From 06-APR-10 16:30:00 to 06-APR-10 16:30:00 (CST-6)
Location: FIFIELD
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MARION, IOWA
From 06-APR-10 16:42:00 to 06-APR-10 16:42:00 (CST-6)
Location: PELLA
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in POWESHIEK, IOWA
From 06-APR-10 16:59:00 to 06-APR-10 16:59:00 (CST-6)
Location: GRINNELL
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MARION, IOWA
From 06-APR-10 16:57:00 to 06-APR-10 16:57:00 (CST-6)
Location: PLEASANTVILLE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in POWESHIEK, IOWA
From 06-APR-10 17:02:00 to 06-APR-10 17:02:00 (CST-6)
Location: GRINNELL
Magnitude: 1.50 
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in TAMA, IOWA
From 06-APR-10 17:14:00 to 06-APR-10 17:14:00 (CST-6)
Location: TAMA ARPT
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in WARREN, IOWA
From 06-APR-10 17:20:00 to 06-APR-10 17:20:00 (CST-6)
Location: NEW VIRGINIA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in WARREN, IOWA
From 06-APR-10 17:22:00 to 06-APR-10 17:22:00 (CST-6)
Location: NEW VIRGINIA
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Public