A strong southerly flow of very moist air pushed into Iowa.  Dew point temperatures rose to the mid 60s to near 70 by late afternoon.  The airmass became relatively unstable, however the dynamics were somewhat limited.  The effective shear was in the 25 to 35 kt range.  The freezing level was between 12,000 and 13,000 feet, however the sounding was quite saturated which limited the hail somewhat.  The CAPE in the -10 to -30 C. layer was in the 200 to 300 J/kg range with the most unstable CAPE in the 1000 to 2000 J/lg range.  Lifted indices were in the -2 to -4 C. range.  A slow moving cold front entered western Iowa from the west during the late afternoon.  Thunderstorms formed along the front and lifted northeast.  Many of the storms produced large amounts of pea size hail, however very few produced any significant size hail.  Most of the hail was in the three quarter to one inch diameter range.    A bow echo segment formed along the east edge of the system and produced scattered reports of high winds.  A semi-tractortrailer was blown off the highway along Interstate 80 at the Stuart exit.  The truck overturned, blocking the highway and injuring the driver.  He was flown to hospital in Des Moines.  High winds snapped power poles southwest of Britt.  A severe thunderstorm in the Lake Mills area produced what appears to be a downburst wind gust that took the roof off of a grain bin and blew down 6 power poles.   A short time later, the same segment produced 61 MPH winds at the Waterloo Airport.

Hail in HANCOCK, IOWA
From 23-MAY-07 16:07:00 to 23-MAY-07 16:07:00 (CST-6)
Location: DUNCAN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Thunderstorm Wind in BUTLER, IOWA
From 23-MAY-07 18:15:00 to 23-MAY-07 18:15:00 (CST-6)
Location: PARKERSBURG
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in HANCOCK, IOWA
From 23-MAY-07 16:25:00 to 23-MAY-07 16:25:00 (CST-6)
Location: GARNER
Magnitude: 57.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in CASS, IOWA
From 23-MAY-07 14:28:00 to 23-MAY-07 14:28:00 (CST-6)
Location: FLETCHER CHAPEL
Magnitude: 1.25 
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in ADAIR, IOWA
From 23-MAY-07 15:58:00 to 23-MAY-07 15:58:00 (CST-6)
Location: HOWE
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Hail in CARROLL, IOWA
From 23-MAY-07 15:25:00 to 23-MAY-07 15:25:00 (CST-6)
Location: GLIDDEN
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Hail in DALLAS, IOWA
From 23-MAY-07 16:54:00 to 23-MAY-07 16:54:00 (CST-6)
Location: ADEL
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Hail in DALLAS, IOWA
From 23-MAY-07 16:19:00 to 23-MAY-07 16:19:00 (CST-6)
Location: KENNEDY
Magnitude: 0.88 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in ADAIR, IOWA
From 23-MAY-07 15:38:00 to 23-MAY-07 15:38:00 (CST-6)
Location: ROSSERDALE
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in ADAIR, IOWA
From 23-MAY-07 15:54:00 to 23-MAY-07 15:54:00 (CST-6)
Location: HOWE
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Thunderstorm Wind in DALLAS, IOWA
From 23-MAY-07 16:15:00 to 23-MAY-07 16:15:00 (CST-6)
Location: DAWSON
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in HANCOCK, IOWA
From 23-MAY-07 16:10:00 to 23-MAY-07 16:10:00 (CST-6)
Location: STILSON
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in HANCOCK, IOWA
From 23-MAY-07 16:15:00 to 23-MAY-07 16:30:00 (CST-6)
Location: GARNER
Magnitude: 70.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in BLACK HAWK, IOWA
From 23-MAY-07 18:54:00 to 23-MAY-07 18:54:00 (CST-6)
Location: (ALO)WATERLOO MUNI A
Magnitude: 53.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in FRANKLIN, IOWA
From 23-MAY-07 17:55:00 to 23-MAY-07 17:55:00 (CST-6)
Location: HAMPTON
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Thunderstorm Wind in WINNEBAGO, IOWA
From 23-MAY-07 17:30:00 to 23-MAY-07 17:30:00 (CST-6)
Location: LAKE MILLS
Magnitude: 70.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Newspaper