Warm and very humid air moved north into Iowa during the day on the 17th.  Surface temperatures warmed into the mid 80s to low 90s, with dew point temperatures in the mid 70s to around 80 by mid afternoon.  A weak cold front was approaching the state at the same time that a negatively tilted shortwave lifted northeast across the upper Midwest.  The atmosphere became very unstable with lifted indices falling to around -9 C.  CAPE rose to between 3000 and 4500 J/kg by late afternoon.  Downdraft CAPE was around 1500 J/kg with available CAPE in the -10 to -30 C layer of the atmosphere between 800 and 1100 J/kg.  With the humid airmass, precipitable water values were between 1.8 and 2 inches, resulting in a relatively low LCL level of 750 to 1000 meters.  The freezing level was relatively high, around 14,500 feet.  The shear was not all that strong, ranging from around 35 kts over northern Iowa to 20 over the southwest.  Thunderstorms fired up initially during the mid to late afternoon hours.  The storms consolidated into a solid line during the evening and advanced east-southeast across the state.  During the early stages of the development, the thunderstorms produced several tornadoes.  One touched down briefly near Lakota in Kossuth County along U.S. Highway 169.  A second tornado tracked from southwest of Lakota to north of the city.  A third tornado was on the ground briefly east of Rake in Winnebago County.  The storms then transitioned into more of a wind and hail event.  Due to the warm conditions aloft, most of the hail was only around in inch or so in diameter.  Golf ball size hail fell in the Buffalo Center area of Winnebago County.  The largest hail was a report of baseball size hail west of Ledyard in Kossuth County.  Winds increased as the evening went on and the system accelerated.  Tree damage was reported in several locations with winds gusting in the 60 to 70 MPH range.

Thunderstorm Wind in HANCOCK, IOWA
From 17-JUN-10 20:02:00 to 17-JUN-10 20:02:00 (CST-6)
Location: KANAWHA
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds were reported near 60 MPH with hail falling.

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 16:37:00 to 17-JUN-10 16:37:00 (CST-6)
Location: STEVENS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Dime to nickel size hail was also reported at this time.

Hail in EMMET, IOWA
From 17-JUN-10 15:13:00 to 17-JUN-10 15:13:00 (CST-6)
Location: RINGSTED
Magnitude: 0.88 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 16:10:00 to 17-JUN-10 16:10:00 (CST-6)
Location: GERLED
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 16:32:00 to 17-JUN-10 16:32:00 (CST-6)
Location: LEDYARD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Reports of a violently rotating wall cloud with multiple brief funnels.

Thunderstorm Wind in KOSSUTH, IOWA
From 17-JUN-10 19:25:00 to 17-JUN-10 19:25:00 (CST-6)
Location: ALGONA
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several large trees were blown down in Algona.

Hail in HANCOCK, IOWA
From 17-JUN-10 20:02:00 to 17-JUN-10 20:02:00 (CST-6)
Location: KANAWHA
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in AUDUBON, IOWA
From 17-JUN-10 22:30:00 to 17-JUN-10 22:30:00 (CST-6)
Location: EXIRA
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Public

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 16:10:00 to 17-JUN-10 16:10:00 (CST-6)
Location: GERLED
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

The funnel cloud was lowering at the time of this report.

Tornado in WINNEBAGO, IOWA
From 17-JUN-10 17:05:00 to 17-JUN-10 17:06:00 (CST-6)
Location: RAKE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A cone tornado was on the ground briefly east of Rake.

Thunderstorm Wind in CERRO GORDO, IOWA
From 17-JUN-10 20:10:00 to 17-JUN-10 20:10:00 (CST-6)
Location: CLEAR LAKE
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees were blown down in the city.

Thunderstorm Wind in CERRO GORDO, IOWA
From 17-JUN-10 20:17:00 to 17-JUN-10 20:17:00 (CST-6)
Location: PLYMOUTH
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees were blown down.

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:37:00 to 17-JUN-10 15:37:00 (CST-6)
Location: SENECA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

The funnel cloud was reportedly under a well defined wall cloud.

Tornado in KOSSUTH, IOWA
From 17-JUN-10 16:24:00 to 17-JUN-10 16:25:00 (CST-6)
Location: STEVENS
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Tornado was spotted briefly.

Hail in SAC, IOWA
From 17-JUN-10 18:50:00 to 17-JUN-10 18:50:00 (CST-6)
Location: NEMAHA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in POCAHONTAS, IOWA
From 17-JUN-10 19:20:00 to 17-JUN-10 19:20:00 (CST-6)
Location: ROLFE
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several large tree limbs were blown down in town along with one power line.

Hail in WINNEBAGO, IOWA
From 17-JUN-10 16:40:00 to 17-JUN-10 16:40:00 (CST-6)
Location: BUFFALO CENTER
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Public

Thunderstorm Wind in WRIGHT, IOWA
From 17-JUN-10 21:10:00 to 17-JUN-10 21:10:00 (CST-6)
Location: DOWS
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Tornado in KOSSUTH, IOWA
From 17-JUN-10 16:11:00 to 17-JUN-10 16:12:00 (CST-6)
Location: GERLED
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Tornado touched down briefly west of Lakota, then lifted.

Thunderstorm Wind in CERRO GORDO, IOWA
From 17-JUN-10 20:15:00 to 17-JUN-10 20:15:00 (CST-6)
Location: MASON CITY
Magnitude: 51.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Five inch diameter branch down on 9th St.  Several branches down around the city.

Thunderstorm Wind in CERRO GORDO, IOWA
From 17-JUN-10 20:05:00 to 17-JUN-10 20:05:00 (CST-6)
Location: (MCW)MASON CITY MUNI
Magnitude: 50.00 MG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: ASOS

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:40:00 to 17-JUN-10 15:40:00 (CST-6)
Location: SWEA CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in PALO ALTO, IOWA
From 17-JUN-10 18:09:00 to 17-JUN-10 18:09:00 (CST-6)
Location: CURLEW
Magnitude: 0.88 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Broadcast Media

Nickel size hail and heavy rain.

Thunderstorm Wind in WINNEBAGO, IOWA
From 17-JUN-10 19:30:00 to 17-JUN-10 19:30:00 (CST-6)
Location: FOREST CITY
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Newspaper

High winds cause tree damage and damage to houses.

Hail in KOSSUTH, IOWA
From 17-JUN-10 16:12:00 to 17-JUN-10 16:12:00 (CST-6)
Location: LEDYARD
Magnitude: 3.00 
Property damage: 15.00K
Crop damage: 50.00K
Reported by: Newspaper

Hail in KOSSUTH, IOWA
From 17-JUN-10 16:14:00 to 17-JUN-10 16:14:00 (CST-6)
Location: LEDYARD
Magnitude: 2.75 
Property damage: 20.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:58:00 to 17-JUN-10 15:58:00 (CST-6)
Location: STEVENS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:55:00 to 17-JUN-10 15:55:00 (CST-6)
Location: SENECA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in KOSSUTH, IOWA
From 17-JUN-10 19:37:00 to 17-JUN-10 19:37:00 (CST-6)
Location: HANNA
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in PALO ALTO, IOWA
From 17-JUN-10 18:40:00 to 17-JUN-10 18:40:00 (CST-6)
Location: CYLINDER
Magnitude: 0.88 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Broadcast Media

Hail in KOSSUTH, IOWA
From 17-JUN-10 15:35:00 to 17-JUN-10 15:35:00 (CST-6)
Location: SWEA CITY
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Hail in WINNEBAGO, IOWA
From 17-JUN-10 16:25:00 to 17-JUN-10 16:25:00 (CST-6)
Location: RAKE
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Fire Department/Rescue

Thunderstorm Wind in WRIGHT, IOWA
From 17-JUN-10 20:57:00 to 17-JUN-10 20:57:00 (CST-6)
Location: CLARION
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Large trees were downed, blocking two lanes of traffic.

Thunderstorm Wind in CARROLL, IOWA
From 17-JUN-10 20:53:00 to 17-JUN-10 20:53:00 (CST-6)
Location: CARROLL NEU ARPT
Magnitude: 54.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: AWOS

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:58:00 to 17-JUN-10 15:58:00 (CST-6)
Location: LONE ROCK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 17-JUN-10 15:30:00 to 17-JUN-10 15:30:00 (CST-6)
Location: SWEA CITY
Magnitude: 0.88 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 17-JUN-10 15:45:00 to 17-JUN-10 15:45:00 (CST-6)
Location: SENECA
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 17-JUN-10 16:18:00 to 17-JUN-10 16:18:00 (CST-6)
Location: STEVENS
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Storm Chaser

Walnut size hail was reported.

Thunderstorm Wind in CERRO GORDO, IOWA
From 17-JUN-10 20:14:00 to 17-JUN-10 20:14:00 (CST-6)
Location: MASON CITY
Magnitude: 57.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees were blown down in several areas of the city.

Thunderstorm Wind in KOSSUTH, IOWA
From 17-JUN-10 19:15:00 to 17-JUN-10 19:15:00 (CST-6)
Location: WESLEY
Magnitude: 65.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Winds were estimated at 70 to 80 MPH.

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:47:00 to 17-JUN-10 15:47:00 (CST-6)
Location: SWEA CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The funnel cloud was reported to be rotating and lowering.

Thunderstorm Wind in HARDIN, IOWA
From 17-JUN-10 21:42:00 to 17-JUN-10 21:42:00 (CST-6)
Location: OWASA
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement estimated winds near 60 MPH.

Hail in KOSSUTH, IOWA
From 17-JUN-10 16:08:00 to 17-JUN-10 16:08:00 (CST-6)
Location: LAKOTA
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:58:00 to 17-JUN-10 15:58:00 (CST-6)
Location: BANCROFT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

The funnel cloud was about half way to the ground.

Thunderstorm Wind in HUMBOLDT, IOWA
From 17-JUN-10 20:04:00 to 17-JUN-10 20:04:00 (CST-6)
Location: RUTLAND
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Trees up to 12 inches in diameter were blown down.

Funnel Cloud in KOSSUTH, IOWA
From 17-JUN-10 15:35:00 to 17-JUN-10 15:35:00 (CST-6)
Location: WHITTEMORE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Reports of rotating rain curtains and a brief funnel.