A very unstable air mass was located over Iowa during the afternoon of the 18th.  Low pressure moved across the northern U.S. with a trailing cold front extending south from the low.  A warm front had lifted north into Iowa during the afternoon.    Temperatures warmed well into the 80s over the south half of Iowa, with surface dew point temperatures in the upper 60s to low 70s.  This produced lifted indices of -5 C. and below.  During the late afternoon thunderstorms erupted east of the approaching cold front.  A line of thunderstorms developed rapidly and produced numerous reports of hail ranging from three-quarters of an inch up to golf ball in size.  The line progressed east into central and eventually eastern Iowa before it  weakened.  The system began to become more of a wind system after sunset.  Wind gusts of 60 MPH were reported in south central into parts of central Iowa.  The most significant damage occurred in Marion County where high winds downed power pols west of Attica.

Hail in GUTHRIE, IOWA
From 18-SEP-02 18:30:00 to 18-SEP-02 18:30:00 (CST)
Location: GUTHRIE CENTER
Magnitude: 1.00 
Property damage: 5K
Crop damage: 3K
Reported by: OFFICIAL NWS OBS.

Hail in MARION, IOWA
From 18-SEP-02 20:47:00 to 18-SEP-02 20:47:00 (CST)
Location: KNOXVILLE
Magnitude: 0.88 
Property damage: 3K
Crop damage: 1K
Reported by: LAW ENFORCEMENT

Hail in GUTHRIE, IOWA
From 18-SEP-02 18:30:00 to 18-SEP-02 18:30:00 (CST)
Location: GUTHRIE CENTER
Magnitude: 1.75 
Property damage: 20K
Crop damage: 10K
Reported by: TRAINED SPOTTER

Hail in UNION, IOWA
From 18-SEP-02 18:50:00 to 18-SEP-02 18:50:00 (CST)
Location: AFTON
Magnitude: 1.00 
Property damage: 5K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MARION, IOWA
From 18-SEP-02 20:07:00 to 18-SEP-02 20:07:00 (CST)
Location: MELCHER
Magnitude: 52 E
Property damage: 5K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Hail in UNION, IOWA
From 18-SEP-02 18:25:00 to 18-SEP-02 18:25:00 (CST)
Location: KENT
Magnitude: 0.88 
Property damage: 2K
Reported by: LAW ENFORCEMENT

Hail in MARION, IOWA
From 18-SEP-02 20:09:00 to 18-SEP-02 20:09:00 (CST)
Location: MELCHER
Magnitude: 0.88 
Property damage: 3K
Crop damage: 1K
Reported by: LAW ENFORCEMENT

Hail in BOONE, IOWA
From 18-SEP-02 19:45:00 to 18-SEP-02 19:45:00 (CST)
Location: OGDEN
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Hail in ADAIR, IOWA
From 18-SEP-02 18:20:00 to 18-SEP-02 18:20:00 (CST)
Location: GREENFIELD
Magnitude: 1.75 
Property damage: 40K
Crop damage: 10K
Reported by: BROADCAST MEDIA

Hail in MARION, IOWA
From 18-SEP-02 20:05:00 to 18-SEP-02 20:05:00 (CST)
Location: DALLAS
Magnitude: 0.88 
Property damage: 3K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in LUCAS, IOWA
From 18-SEP-02 20:05:00 to 18-SEP-02 20:05:00 (CST)
Location: OAKLEY
Magnitude: 52 E
Property damage: 5K
Crop damage: 2K
Reported by: AMATEUR RADIO

Hail in MONROE, IOWA
From 18-SEP-02 19:41:00 to 18-SEP-02 19:41:00 (CST)
Location: ALBIA
Magnitude: 0.88 
Property damage: 3K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in CLARKE, IOWA
From 18-SEP-02 19:36:00 to 18-SEP-02 19:38:00 (CST)
Location: LIBERTY
Magnitude: 52 E
Property damage: 5K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Hail in ADAIR, IOWA
From 18-SEP-02 18:15:00 to 18-SEP-02 18:15:00 (CST)
Location: ORIENT
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Hail in ADAIR, IOWA
From 18-SEP-02 18:05:00 to 18-SEP-02 18:05:00 (CST)
Location: ADAIR
Magnitude: 1.75 
Property damage: 25K
Crop damage: 10K
Reported by: TRAINED SPOTTER

Hail in ADAIR, IOWA
From 18-SEP-02 18:15:00 to 18-SEP-02 18:15:00 (CST)
Location: GREENFIELD
Magnitude: 0.75 
Reported by: LAW ENFORCEMENT

Hail in TAYLOR, IOWA
From 18-SEP-02 18:00:00 to 18-SEP-02 18:00:00 (CST)
Location: LENOX
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in WARREN, IOWA
From 18-SEP-02 19:36:00 to 18-SEP-02 19:36:00 (CST)
Location: LIBERTY CENTER
Magnitude: 0.75 
Reported by: LAW ENFORCEMENT

Hail in CLARKE, IOWA
From 18-SEP-02 19:02:00 to 18-SEP-02 19:02:00 (CST)
Location: MURRAY
Magnitude: 0.88 
Property damage: 3K
Reported by: TRAINED SPOTTER

Hail in GUTHRIE, IOWA
From 18-SEP-02 18:58:00 to 18-SEP-02 18:58:00 (CST)
Location: ADAIR
Magnitude: 1.75 
Property damage: 20K
Crop damage: 10K
Reported by: TRAINED SPOTTER

Hail in DALLAS, IOWA
From 18-SEP-02 19:02:00 to 18-SEP-02 19:02:00 (CST)
Location: LINDEN
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MARION, IOWA
From 18-SEP-02 21:00:00 to 18-SEP-02 21:00:00 (CST)
Location: ATTICA
Magnitude: 52 E
Property damage: 5K
Crop damage: 2K
Reported by: EMERGENCY MANAGER

Hail in CLARKE, IOWA
From 18-SEP-02 19:27:00 to 18-SEP-02 19:27:00 (CST)
Location: MURRAY
Magnitude: 0.75 
Reported by: LAW ENFORCEMENT

Hail in WARREN, IOWA
From 18-SEP-02 19:34:00 to 18-SEP-02 19:34:00 (CST)
Location: NEW VIRGINIA
Magnitude: 1.75 
Property damage: 20K
Crop damage: 10K
Reported by: LAW ENFORCEMENT

Hail in ADAIR, IOWA
From 18-SEP-02 19:10:00 to 18-SEP-02 19:10:00 (CST)
Location: ORIENT
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in POLK, IOWA
From 18-SEP-02 21:40:00 to 18-SEP-02 21:40:00 (CST)
Location: ALLEMAN
Magnitude: 52 E
Property damage: 5K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Hail in POLK, IOWA
From 18-SEP-02 21:48:00 to 18-SEP-02 21:48:00 (CST)
Location: ELKHART
Magnitude: 0.88 
Property damage: 3K
Reported by: AMATEUR RADIO