A very hot and unstable airmass was over Iowa during the afternoon of the 25th into the early morning of the 26th.  CAPE values were close to 4000 J/kg, though the airmass was quite capped with 700 mb temperatures around +12 C.  A cold front was weakening as it approached from the north.  The front itself did not make it into Iowa until the morning of the 26th, however thunderstorms that fired along the front the previous night formed an outflow boundary across Iowa by the morning of the 25th.  By the evening of the 25th, the boundary had lifted north into the central part of the state  Thunderstorms fired along the boundary and also formed into an area of relative weakening of the cap over southeast Iowa.  There were several reported microburst events during the night.  One of the most destructive was over Story County, in Story City, where several hundred trees were toppled by the high winds.  Damage was reported to 47 homes in and around the city as well.  Most of the damage was minor.  Three businesses were also affected.   Power was knocked out in some places for up to 36 hours.  Between 3:30-3:45 a.m. on August 26, 2003, a swath of downburst winds struck Story City, Iowa and nearby farms.  A National Weather Service damage survey indicated that the path of wind damage was about one mile wide, with the strongest winds probably occurring within Story City.  The path of continuous tree damage was about 10 miles long, starting about 5 miles west of Story City near the Story/Boone county line.  The damage path was mainly north of highway E18, and then east of Story City it followed highway E15 for about 3 miles.  There was one injury as a semi-tractortrailer truck was overturned.  The driver was pinned and ended up taken to the hospital.  Three poultry confinement buildings and a grain bin were destroyed in the Story City area.   Elsewhere, high winds overturned a semi-tractortrailer truck in Davis County.  There were numerous reports of trees and power lines down from northwest, into central, and southeast Iowa.  A few reports of hail were received, but the largest hail was only an inch and one quarter in diameter.  That fell northeast of St. Anthony in Marshall County.

Thunderstorm Wind in STORY, IOWA
From 26-AUG-03 02:45:00 to 26-AUG-03 02:45:00 (CST)
Location: STORY CITY
Magnitude: 50 EG
Property damage: 5K
Reported by: UNKNOWN

Thunderstorm Wind in STORY, IOWA
From 26-AUG-03 05:30:00 to 26-AUG-03 05:30:00 (CST)
Location: COLLINS
Magnitude: 52 EG
Property damage: 5K
Crop damage: 2K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in DAVIS, IOWA
From 25-AUG-03 20:00:00 to 25-AUG-03 20:00:00 (CST)
Location: BELKNAP
Magnitude: 52 EG
Property damage: 1K
Crop damage: 10K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in HARDIN, IOWA
From 26-AUG-03 03:07:00 to 26-AUG-03 03:07:00 (CST)
Location: HUBBARD
Magnitude: 52 EG
Property damage: 5K
Crop damage: 2K
Reported by: UNKNOWN

Thunderstorm Wind in STORY, IOWA
From 26-AUG-03 02:50:00 to 26-AUG-03 02:50:00 (CST)
Location: STORY CITY
Magnitude: 57 EG
Property damage: 25K
Crop damage: 5K
Reported by: UNKNOWN

Thunderstorm Wind in HARDIN, IOWA
From 26-AUG-03 03:20:00 to 26-AUG-03 03:20:00 (CST)
Location: NEW PROVIDENCE
Magnitude: 50 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in DAVIS, IOWA
From 25-AUG-03 19:30:00 to 25-AUG-03 19:30:00 (CST)
Location: BLOOMFIELD
Magnitude: 50 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DAVIS, IOWA
From 25-AUG-03 20:28:00 to 25-AUG-03 20:28:00 (CST)
Location: FLORIS
Magnitude: 54 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DAVIS, IOWA
From 25-AUG-03 20:30:00 to 25-AUG-03 20:30:00 (CST)
Location: BLOOMFIELD
Magnitude: 57 EG
Property damage: 15K
Crop damage: 10K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in STORY, IOWA
From 25-AUG-03 17:56:00 to 25-AUG-03 17:56:00 (CST)
Location: AMES ARPT
Magnitude: 51 MG
Property damage: 2K
Reported by: AWOS,ASOS,MESONET,ETC

Hail in POCAHONTAS, IOWA
From 25-AUG-03 18:30:00 to 25-AUG-03 18:30:00 (CST)
Location: PALMER
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MARSHALL, IOWA
From 25-AUG-03 18:35:00 to 25-AUG-03 18:35:00 (CST)
Location: CLEMONS
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WAPELLO, IOWA
From 25-AUG-03 18:35:00 to 25-AUG-03 18:35:00 (CST)
Location: AGENCY
Magnitude: 61 EG
Property damage: 5K
Crop damage: 20K
Reported by: TRAINED SPOTTER

Hail in MARSHALL, IOWA
From 25-AUG-03 18:45:00 to 25-AUG-03 18:45:00 (CST)
Location: CLEMONS
Magnitude: 1.50 
Property damage: 5K
Crop damage: 20K
Reported by: TRAINED SPOTTER

Hail in MARSHALL, IOWA
From 25-AUG-03 18:52:00 to 25-AUG-03 18:52:00 (CST)
Location: ST ANTHONY
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in MARSHALL, IOWA
From 25-AUG-03 18:54:00 to 25-AUG-03 18:54:00 (CST)
Location: ST ANTHONY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in MARSHALL, IOWA
From 25-AUG-03 18:57:00 to 25-AUG-03 18:57:00 (CST)
Location: ST ANTHONY
Magnitude: 1.25 
Property damage: 5K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in MARSHALL, IOWA
From 25-AUG-03 19:07:00 to 25-AUG-03 19:07:00 (CST)
Location: LISCOMB
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WAPELLO, IOWA
From 25-AUG-03 19:10:00 to 25-AUG-03 19:10:00 (CST)
Location: AGENCY
Magnitude: 50 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in STORY, IOWA
From 25-AUG-03 17:58:00 to 25-AUG-03 17:58:00 (CST)
Location: AMES ARPT
Magnitude: 57 MG
Property damage: 5K
Crop damage: 2K
Reported by: AWOS,ASOS,MESONET,ETC

Thunderstorm Wind in STORY, IOWA
From 25-AUG-03 18:00:00 to 25-AUG-03 18:00:00 (CST)
Location: KELLEY
Magnitude: 50 EG
Property damage: 2K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in WAPELLO, IOWA
From 25-AUG-03 18:00:00 to 25-AUG-03 18:00:00 (CST)
Location: OTTUMWA
Magnitude: 50 EG
Property damage: 10K
Reported by: UNKNOWN

Thunderstorm Wind in STORY, IOWA
From 25-AUG-03 18:12:00 to 25-AUG-03 18:12:00 (CST)
Location: KELLEY
Magnitude: 50 EG
Property damage: 3K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in STORY, IOWA
From 25-AUG-03 18:25:00 to 25-AUG-03 18:25:00 (CST)
Location: NEVADA
Magnitude: 52 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DALLAS, IOWA
From 25-AUG-03 18:29:00 to 25-AUG-03 18:29:00 (CST)
Location: WOODWARD
Magnitude: 50 EG
Property damage: 5K
Reported by: AMATEUR RADIO

Thunderstorm Wind in DAVIS, IOWA
From 25-AUG-03 21:03:00 to 25-AUG-03 21:03:00 (CST)
Location: BLOOMFIELD
Magnitude: 52 EG
Property damage: 10K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in HAMILTON, IOWA
From 26-AUG-03 00:59:00 to 26-AUG-03 00:59:00 (CST)
Location: WEBSTER CITY
Magnitude: 65 EG
Property damage: 25K
Crop damage: 10K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in STORY, IOWA
From 26-AUG-03 02:45:00 to 26-AUG-03 02:45:00 (CST)
Location: STORY CITY
Magnitude: 65 EG
Property damage: 150K
Crop damage: 25K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in HAMILTON, IOWA
From 26-AUG-03 03:00:00 to 26-AUG-03 03:00:00 (CST)
Location: RANDALL
Magnitude: 52 EG
Property damage: 5K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in STORY, IOWA
From 26-AUG-03 02:45:00 to 26-AUG-03 02:45:00 (CST)
Location: STORY CITY
Magnitude: 50 EG
Property damage: 37K
Crop damage: 10K
Reported by: BROADCAST MEDIA