A semi-stationary frontal boundary remained in place across southern Iowa while a secondary boundary was stretched from eastern South Dakota into northeast Iowa.  The airmass became very unstable with lifted indices falling to -10 to -15 C and most unstable CAPE rising to 5000 to 6000 J/kg.  Zero to 3 km CAPE rose to over 200 J/kg in northern Iowa by the late afternoon.  Surface temperatures rose to the 80s to low 90s, as dew point values reached the upper 60s to mid 70s.  Wind fields were somewhat weak, however effective shear was in the 35 to 50 kt range by late afternoon.  The amount of CAPE in the -10 to -30 layer of the atmosphere rose to over 400 J/kg by late afternoon.  Thunderstorms erupted in two places initially.  The first was along the northern boundary.  However the severe storms with this round remained to the north of Iowa.  A second round formed north of the southern boundary along the edge of the mid level cap.  The storms became severe and produced high winds and hail.  Thunderstorms from farther west moved into Iowa later in the evening and became severe.  The storms produced a weak Derecho.  Widespread winds of 60 to 70 MPH occurred with these storms, along with numerous reports of hail of 1 to 2 inches in diameter.  The initial round of storms produced large hail and gusty winds from southwest into central Iowa.  The second round resulted in winds of 60 to 70 MPH and large hail from central into southeast Iowa.  The highest wind gust was 74 MPH, measured at an RWIS site near Ankeny in Polk County.  The wind damage was largely to trees and power lines, with spotty reports of small shed and minor building damage.  A semi-tractor trailer was blown off of Interstate 35 near Highway 210 in Story County.  The high winds ripped siding off of a house in Ankeny in Polk county, and windows were blown out of a house in Colfax in Jasper County.  Thunderstorms rekindled on the back side of the main thunderstorm area after sunrise.  A few storms became severe and produced 60 MPH winds and golf ball size hail as they moved from The Fort Dodge area into Story County.

Hail in CASS, IOWA
From 17-JUN-09 20:33:00 to 17-JUN-09 20:38:00 (CST-6)
Location: ANITA MUNI ARPT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in AUDUBON, IOWA
From 17-JUN-09 21:06:00 to 17-JUN-09 21:06:00 (CST-6)
Location: KENFIELD
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Hail in ADAIR, IOWA
From 17-JUN-09 21:31:00 to 17-JUN-09 21:31:00 (CST-6)
Location: ADAIR
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Broadcast Media

Hail in ADAIR, IOWA
From 17-JUN-09 21:28:00 to 17-JUN-09 21:35:00 (CST-6)
Location: ADAIR
Magnitude: 1.25 
Property damage: 10.00K
Crop damage: 25.00K
Reported by: Fire Department/Rescue

The Adair Fire Department reported the hail lasted several minutes.

Hail in POLK, IOWA
From 17-JUN-09 21:43:00 to 17-JUN-09 21:43:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 3.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 17-JUN-09 21:45:00 to 17-JUN-09 21:45:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 3.00K
Reported by: Trained Spotter

Hail in GUTHRIE, IOWA
From 17-JUN-09 21:53:00 to 17-JUN-09 21:53:00 (CST-6)
Location: CASEY
Magnitude: 2.00 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Hail in ADAIR, IOWA
From 17-JUN-09 21:37:00 to 17-JUN-09 21:37:00 (CST-6)
Location: ADAIR
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Amateur Radio

Hail in POLK, IOWA
From 17-JUN-09 21:50:00 to 17-JUN-09 21:50:00 (CST-6)
Location: CARNEY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:14:00 to 18-JUN-09 01:14:00 (CST-6)
Location: (DSM)DES MOINES INTL
Magnitude: 50.00 MG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:14:00 to 18-JUN-09 01:14:00 (CST-6)
Location: ANKENY
Magnitude: 64.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in WAPELLO, IOWA
From 18-JUN-09 01:22:00 to 18-JUN-09 01:22:00 (CST-6)
Location: OTTUMWA
Magnitude: 57.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Road signs were blown over.

Thunderstorm Wind in JASPER, IOWA
From 18-JUN-09 01:25:00 to 18-JUN-09 01:25:00 (CST-6)
Location: PRAIRIE CITY
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in JASPER, IOWA
From 18-JUN-09 01:23:00 to 18-JUN-09 01:23:00 (CST-6)
Location: COLFAX
Magnitude: 51.00 MG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in WAPELLO, IOWA
From 18-JUN-09 01:35:00 to 18-JUN-09 01:35:00 (CST-6)
Location: ELDON
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:02:00 to 18-JUN-09 01:02:00 (CST-6)
Location: ANKENY
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: ANKENY
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: NWS Employee

Roof damage occurred throughout the neighborhood.  Siding was ripped off of some houses.

Thunderstorm Wind in WEBSTER, IOWA
From 18-JUN-09 07:05:00 to 18-JUN-09 07:05:00 (CST-6)
Location: FT DODGE
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in JASPER, IOWA
From 18-JUN-09 01:25:00 to 18-JUN-09 01:25:00 (CST-6)
Location: GODDARD
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in MARION, IOWA
From 18-JUN-09 01:30:00 to 18-JUN-09 01:30:00 (CST-6)
Location: RED ROCK
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A power pole was snapped off.

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 08:05:00 to 18-JUN-09 08:05:00 (CST-6)
Location: MC CALLSBURG
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STORY, IOWA
From 18-JUN-09 08:11:00 to 18-JUN-09 08:11:00 (CST-6)
Location: MC CALLSBURG
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Thunderstorm Wind in MARSHALL, IOWA
From 17-JUN-09 23:45:00 to 17-JUN-09 23:45:00 (CST-6)
Location: LISCOMB
Magnitude: 57.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Newspaper

Tree and power line damage occurred near Liscomb.

Thunderstorm Wind in AUDUBON, IOWA
From 17-JUN-09 21:00:00 to 17-JUN-09 21:00:00 (CST-6)
Location: GRAY
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Newspaper

High winds in the town of Gray blew over trees and some traffic signs.

Hail in ADAIR, IOWA
From 17-JUN-09 22:12:00 to 17-JUN-09 22:12:00 (CST-6)
Location: HOWE
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: Broadcast Media

Hail in POLK, IOWA
From 17-JUN-09 22:05:00 to 17-JUN-09 22:05:00 (CST-6)
Location: BONDURANT
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Amateur Radio

Amateur Radio operator reported one inch diameter hail at the intersection of northeast 78th and Highway 65 in Bondurant.

Hail in MADISON, IOWA
From 17-JUN-09 23:10:00 to 17-JUN-09 23:10:00 (CST-6)
Location: EAST PERU
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Hail in MADISON, IOWA
From 17-JUN-09 23:25:00 to 17-JUN-09 23:25:00 (CST-6)
Location: TRURO
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Amateur Radio

Hail in MADISON, IOWA
From 17-JUN-09 22:00:00 to 17-JUN-09 22:00:00 (CST-6)
Location: WINTERSET ARPT
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 10.00K
Reported by: COOP Observer

Hail in ADAIR, IOWA
From 17-JUN-09 21:30:00 to 17-JUN-09 21:30:00 (CST-6)
Location: ADAIR
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Hail in POLK, IOWA
From 17-JUN-09 21:45:00 to 17-JUN-09 21:45:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in CLARKE, IOWA
From 17-JUN-09 23:45:00 to 17-JUN-09 23:45:00 (CST-6)
Location: JAMISON
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Thunderstorm Wind in MADISON, IOWA
From 17-JUN-09 23:10:00 to 17-JUN-09 23:10:00 (CST-6)
Location: PERU
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Madison County law enforcement reports trees blown down over the road at 3010 Rustic Ave.

Hail in CARROLL, IOWA
From 17-JUN-09 23:58:00 to 17-JUN-09 23:58:00 (CST-6)
Location: LIDDERDALE
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Thunderstorm Wind in MADISON, IOWA
From 17-JUN-09 23:05:00 to 17-JUN-09 23:05:00 (CST-6)
Location: PERU
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Several tree branches were down at the intersection of G68 and R21.

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:08:00 to 18-JUN-09 01:08:00 (CST-6)
Location: ANKENY
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous tree branches up to 6 inches in diameter down.  Power was out in many areas and some street flooding occurred.

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A metal outbuilding was blown over at a trailer park.

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: ALLEMAN
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Department of Highways

U.S. Highway 69 was closed due to power lines over the highway between Highway 210 and Highway 87.

Hail in MARION, IOWA
From 18-JUN-09 01:48:00 to 18-JUN-09 01:48:00 (CST-6)
Location: KNOXVILLE ARPT
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Public

Hail in LUCAS, IOWA
From 18-JUN-09 00:01:00 to 18-JUN-09 00:01:00 (CST-6)
Location: CHARITON
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Thunderstorm Wind in MARION, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: RED ROCK
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A power pole was snapped.

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: CARNEY
Magnitude: 52.00 MG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured by anemometer.

Thunderstorm Wind in MADISON, IOWA
From 17-JUN-09 23:10:00 to 17-JUN-09 23:10:00 (CST-6)
Location: EAST PERU
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in MAHASKA, IOWA
From 18-JUN-09 00:38:00 to 18-JUN-09 00:38:00 (CST-6)
Location: OSKALOOSA
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 00:53:00 to 18-JUN-09 00:53:00 (CST-6)
Location: POLK CITY
Magnitude: 50.00 MG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: POLK CITY
Magnitude: 52.00 MG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in BOONE, IOWA
From 18-JUN-09 00:42:00 to 18-JUN-09 00:42:00 (CST-6)
Location: BOONE MUNI ARPT
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in BOONE, IOWA
From 18-JUN-09 00:53:00 to 18-JUN-09 00:53:00 (CST-6)
Location: MADRID
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:08:00 to 18-JUN-09 01:08:00 (CST-6)
Location: ANKENY
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:02:00 to 18-JUN-09 01:02:00 (CST-6)
Location: CLIVE
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:06:00 to 18-JUN-09 01:06:00 (CST-6)
Location: ANKENY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in POLK, IOWA
From 18-JUN-09 01:10:00 to 18-JUN-09 01:10:00 (CST-6)
Location: URBANDALE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 1.00K
Reported by: COOP Observer

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 01:05:00 to 18-JUN-09 01:05:00 (CST-6)
Location: HUXLEY
Magnitude: 56.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The power was out in Huxley. Pea size hail was observed.

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:10:00 to 18-JUN-09 01:10:00 (CST-6)
Location: BONDURANT
Magnitude: 61.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Reports of a roof blown off of a house and barn at 2nd St. and NE 80th east of Bondurant were received.

Thunderstorm Wind in JASPER, IOWA
From 18-JUN-09 01:17:00 to 18-JUN-09 01:17:00 (CST-6)
Location: VALERIA
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several shingles were blown off the roofs of many homes.  Windows were blown out of one house.

Thunderstorm Wind in ADAIR, IOWA
From 17-JUN-09 21:10:00 to 17-JUN-09 21:10:00 (CST-6)
Location: ARBOR HILL
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A two and one half foot diameter tree was downed.

Thunderstorm Wind in SAC, IOWA
From 17-JUN-09 23:15:00 to 17-JUN-09 23:15:00 (CST-6)
Location: LAKE VIEW
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A medium sized tree was down.

Thunderstorm Wind in BOONE, IOWA
From 18-JUN-09 00:55:00 to 18-JUN-09 00:55:00 (CST-6)
Location: MADRID
Magnitude: 51.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 4 to 6 inch tree branches were down and blown through the neighborhood.

Thunderstorm Wind in BOONE, IOWA
From 18-JUN-09 00:58:00 to 18-JUN-09 00:58:00 (CST-6)
Location: MADRID
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Boone County law enforcement reported 12 inch tree limbs down in Madrid.

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 00:55:00 to 18-JUN-09 00:55:00 (CST-6)
Location: HUXLEY
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread wind damage was reported around Huxley with up to 20 inch limbs down. A shed was blown through a parking lot.

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: HUXLEY
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Large branches and power lines were reported down.

Thunderstorm Wind in STORY, IOWA
From 18-JUN-09 01:00:00 to 18-JUN-09 01:00:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Semi-tractor trailer was blown off Interstate 35 near Highway 210.

Funnel Cloud in MADISON, IOWA
From 17-JUN-09 23:16:00 to 17-JUN-09 23:16:00 (CST-6)
Location: BARNEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Madison County law reported a funnel cloudy near the intersection of Millstream Ave and 305th St.

Thunderstorm Wind in POLK, IOWA
From 18-JUN-09 01:13:00 to 18-JUN-09 01:13:00 (CST-6)
Location: DES MOINES
Magnitude: 51.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter