An outflow boundary remained in place just south of Iowa from the previous nights convection.  The airmass over Iowa became very unstable with high temperatures reaching the low 90s on the 22nd, with dewpoint readings in the mid 70s to low 80s.  Precipitable water values increased to between 2 and 2.2 inches in a band extending from southwest into northeast Iowa as monsoonal moisture was drawn north.  CAPE values were in the 4000 to 5000 J/kg range, with the lifted index between -6 and -8 C on the warm side of the thunderstorm development.  The atmospheric shear was weak, around 20 kts.  CAPE in the -10 to -30 C layer of the atmosphere was around 600 J/kg, but hail production was limited by the 15,500 foot freezing level.  Thunderstorms developed over central into east central and northeast Iowa.  Upscale development took place into a small MCS.  This MCS produced severe weather, mainly in the form of high winds and some small hail.  Damage from the wind was limited to tree damage for the most part.  One storm produced very strong winds in Butler County.  Winds with an estimated speed of 80 MPH tore part of the roof off of a house north of Aplington and also destroyed 6 outbuildings.  Lightning struck an abandon church in Knoxville, setting it on fire.  The fire was brought under control quickly.  Heavy rain fell in the Aplington area of Butler County with 2.5 inches falling in a relatively short period of time.

Thunderstorm Wind in BUTLER, IOWA
From 22-JUL-11 17:37:00 to 22-JUL-11 17:37:00 (CST-6)
Location: APLINGTON
Magnitude: 75.00 EG
Property damage: 500.00K
Crop damage: 100.00K
Reported by: Emergency Manager

House roof was partially ripped off and 6 outbuildings were destroyed with significant tree damage.

Thunderstorm Wind in MARION, IOWA
From 22-JUL-11 19:16:00 to 22-JUL-11 19:16:00 (CST-6)
Location: FIFIELD
Magnitude: 55.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in MARION, IOWA
From 22-JUL-11 18:57:00 to 22-JUL-11 18:57:00 (CST-6)
Location: KNOXVILLE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Emergency Manager

A wind gust of 52 MPH was observed at the same time.

Thunderstorm Wind in HARDIN, IOWA
From 22-JUL-11 18:35:00 to 22-JUL-11 18:35:00 (CST-6)
Location: UNION
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Numerous trees were toppled in Union.

Thunderstorm Wind in BLACK HAWK, IOWA
From 22-JUL-11 18:35:00 to 22-JUL-11 18:35:00 (CST-6)
Location: WATERLOO
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A tree was down at 11th and Washington.

Heavy Rain in BUTLER, IOWA
From 22-JUL-11 18:15:00 to 22-JUL-11 18:15:00 (CST-6)
Location: APLINGTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured rainfall of 2.2 inches and still falling.

Thunderstorm Wind in POWESHIEK, IOWA
From 22-JUL-11 20:15:00 to 22-JUL-11 20:15:00 (CST-6)
Location: GRINNELL
Magnitude: 50.00 MG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: AWOS

Hail in JASPER, IOWA
From 22-JUL-11 20:00:00 to 22-JUL-11 20:00:00 (CST-6)
Location: TURNER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Also with 50 MPH winds.

Thunderstorm Wind in JASPER, IOWA
From 22-JUL-11 19:40:00 to 22-JUL-11 19:40:00 (CST-6)
Location: SULLY
Magnitude: 50.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Mesonet

Law enforcement also reported power lines down.

Thunderstorm Wind in MARION, IOWA
From 22-JUL-11 19:03:00 to 22-JUL-11 19:03:00 (CST-6)
Location: KNOXVILLE
Magnitude: 50.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several reports of power lines down in the city near the racetrack.

Thunderstorm Wind in BUTLER, IOWA
From 22-JUL-11 18:07:00 to 22-JUL-11 18:07:00 (CST-6)
Location: PARKERSBURG
Magnitude: 57.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several reports of trees down around town.  Largest was 14 inches in diameter blocking the highway north of town.

Heavy Rain in BUTLER, IOWA
From 22-JUL-11 19:02:00 to 22-JUL-11 19:02:00 (CST-6)
Location: APLINGTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured rainfall of 2.5 inches for the event.

Lightning in MARION, IOWA
From 22-JUL-11 19:50:00 to 22-JUL-11 19:50:00 (CST-6)
Location: KNOXVILLE
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager