A very unstable situation unfolded during the afternoon of the 18th into the evening hours.  Very warm and fairly moist air was drawn north into Iowa as the warm front that had been to the south of the state the previous two days lifted north of Iowa during the day on the 18th.  Dew point temperatures were in the low to mid 60s over much of Iowa.  In spite of the relatively low dew points, the airmass became quite unstable.  CAPE values were in the 3000 to 4500 J/kg range by the early evening.  A cold front entered the state during the late afternoon hours.  Thunderstorms developed explosively along the cold frontal boundary by early evening.  A nearly solid like of thunderstorms began to move east across the state.  One tornado was reported in Carroll County south of the Glidden area.  The touchdown was brief and occurred in open country.  Much of the severe weather with this event was in the form of hail.  Numerous locations reported hail anywhere from three quarter inch in diameter up to golf ball size.  The largest hail report was received from Emmet County.  Baseball size hail fell south of the Armstrong area, causing considerable damage to roofs and crops in the area.  As the evening progressed, the storms produced more winds, in part due to the collapse of the line.  high winds caused scattered power outages around the state.  A wind gust in Worth County moved a livestock trailer, pushing the trailer sideways.  The line of thunderstorms weakened rapidly as the midnight hour approached.

Hail in WARREN, IOWA
From 18-JUN-01 22:05:00 to 18-JUN-01 22:05:00 (CST)
Location: MILO
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in STORY, IOWA
From 18-JUN-01 21:08:00 to 18-JUN-01 21:08:00 (CST)
Location: STORY CITY
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in WARREN, IOWA
From 18-JUN-01 21:50:00 to 18-JUN-01 21:50:00 (CST)
Location: INDIANOLA
Magnitude: 1.00 
Property damage: 4K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in WINNEBAGO, IOWA
From 18-JUN-01 20:58:00 to 18-JUN-01 20:58:00 (CST)
Location: FOREST CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 18-JUN-01 21:17:00 to 18-JUN-01 21:17:00 (CST)
Location: CLEAR LAKE
Magnitude: 1.75 
Property damage: 10K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in HANCOCK, IOWA
From 18-JUN-01 20:00:00 to 18-JUN-01 20:00:00 (CST)
Location: GARNER
Magnitude: 52 E
Property damage: 2K
Reported by: UNKNOWN

Hail in CRAWFORD, IOWA
From 18-JUN-01 19:25:00 to 18-JUN-01 19:25:00 (CST)
Location: DENISON
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in EMMET, IOWA
From 18-JUN-01 18:37:00 to 18-JUN-01 18:37:00 (CST)
Location: RINGSTED
Magnitude: 1.75 
Property damage: 20K
Crop damage: 10K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in WINNEBAGO, IOWA
From 18-JUN-01 19:43:00 to 18-JUN-01 19:43:00 (CST)
Location: THOMPSON
Magnitude: 61 E
Property damage: 10K
Reported by: EMERGENCY MANAGER

Hail in CRAWFORD, IOWA
From 18-JUN-01 19:22:00 to 18-JUN-01 19:22:00 (CST)
Location: DENISON
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in KOSSUTH, IOWA
From 18-JUN-01 19:45:00 to 18-JUN-01 19:45:00 (CST)
Location: ALGONA
Magnitude: 52 E
Property damage: 3K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in POCAHONTAS, IOWA
From 18-JUN-01 19:00:00 to 18-JUN-01 19:00:00 (CST)
Location: FONDA
Magnitude: 52 E
Property damage: 3K
Reported by: EMERGENCY MANAGER

Hail in STORY, IOWA
From 18-JUN-01 20:58:00 to 18-JUN-01 20:58:00 (CST)
Location: STORY CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: BROADCAST MEDIA

Hail in MARSHALL, IOWA
From 18-JUN-01 21:38:00 to 18-JUN-01 21:38:00 (CST)
Location: ALBION
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Tornado in CARROLL, IOWA
From 18-JUN-01 20:25:00 to 18-JUN-01 20:25:00 (CST)
Location: GLIDDEN
Tornado F-scale: F0
Crop damage: 1K
Reported by: FIRE DEPT/RESCUE SQUAD

Brief touchdown in open area south of town.

Thunderstorm Wind in MARION, IOWA
From 18-JUN-01 22:30:00 to 18-JUN-01 22:30:00 (CST)
Location: TRACY
Magnitude: 54 E
Property damage: 5K
Reported by: EMERGENCY MANAGER

Hail in EMMET, IOWA
From 18-JUN-01 18:46:00 to 18-JUN-01 18:46:00 (CST)
Location: ARMSTRONG
Magnitude: 2.75 
Property damage: 20K
Crop damage: 10K
Reported by: BROADCAST MEDIA

Hail in POLK, IOWA
From 18-JUN-01 21:40:00 to 18-JUN-01 21:40:00 (CST)
Location: ALTOONA
Magnitude: 0.88 
Property damage: 3K
Crop damage: 5K
Reported by: AMATEUR RADIO

Thunderstorm Wind in WORTH, IOWA
From 18-JUN-01 21:45:00 to 18-JUN-01 21:45:00 (CST)
Location: NORTHWOOD
Magnitude: 61 E
Property damage: 10K
Crop damage: 1K
Reported by: LAW ENFORCEMENT

Hail in WORTH, IOWA
From 18-JUN-01 21:35:00 to 18-JUN-01 21:35:00 (CST)
Location: KENSETT
Magnitude: 1.25 
Property damage: 4K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in RINGGOLD, IOWA
From 18-JUN-01 22:23:00 to 18-JUN-01 22:23:00 (CST)
Location: MT AYR
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WRIGHT, IOWA
From 18-JUN-01 20:15:00 to 18-JUN-01 20:15:00 (CST)
Location: CLARION
Magnitude: 50 M
Property damage: 2K
Reported by: BROADCAST MEDIA

Hail in WINNEBAGO, IOWA
From 18-JUN-01 19:43:00 to 18-JUN-01 19:43:00 (CST)
Location: THOMPSON
Magnitude: 1.75 
Property damage: 10K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in DECATUR, IOWA
From 18-JUN-01 22:25:00 to 18-JUN-01 22:25:00 (CST)
Location: LAMONI
Magnitude: 0.75 
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in KOSSUTH, IOWA
From 18-JUN-01 18:40:00 to 18-JUN-01 18:40:00 (CST)
Location: BANCROFT
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in WINNEBAGO, IOWA
From 18-JUN-01 19:45:00 to 18-JUN-01 19:45:00 (CST)
Location: THOMPSON
Magnitude: 1.75 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in HUMBOLDT, IOWA
From 18-JUN-01 20:05:00 to 18-JUN-01 20:05:00 (CST)
Location: HUMBOLDT
Magnitude: 56 E
Property damage: 5K
Reported by: EMERGENCY MANAGER

Hail in STORY, IOWA
From 18-JUN-01 21:10:00 to 18-JUN-01 21:10:00 (CST)
Location: STORY CITY
Magnitude: 1.75 
Property damage: 25K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WORTH, IOWA
From 18-JUN-01 20:00:00 to 18-JUN-01 20:00:00 (CST)
Location: KENSETT
Magnitude: 65 E
Property damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in HANCOCK, IOWA
From 18-JUN-01 20:45:00 to 18-JUN-01 20:45:00 (CST)
Location: WODEN
Magnitude: 52 E
Property damage: 3K
Reported by: UNKNOWN

Hail in WORTH, IOWA
From 18-JUN-01 21:35:00 to 18-JUN-01 21:35:00 (CST)
Location: MANLY
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER