A cold front advanced across the plains and moved into Iowa during the night of the 6th.  The weather situation was quite dynamic for early September.  A low level jet of 50 kts developed ahead of the cold front.  Warm air moved in at 500 mb during the day, which reduced the lapse rate significantly.  There was a lot of CAPE, shear, and helicity in the lowest one to two kilometers of the surface, but parameters were weak above that.  This lead to a mini supercell event.  CAPE values were around 1500 J/kg and lifted indices in the -4 to -5 C. range.  The freezing level was quite high and was in the 15,000 to 15,500 foot range.  A line of thunderstorms that had persisted through the day ahead of the cold front strengthened during the mid and late afternoon hours before pushing east across Iowa.  There was very little in the way of wind with this event with only an isolated event reported in Story County, and no hail reported.  High winds caused tree damage in the Lacona area of Warren County.  The winds were along the track of a tornado that touched down in Lucas County, however there was no evidence that the tornado was on the ground in Warren County.  Several small tornadoes occurred over northwest into central Iowa.  Most of them were brief touchdowns in open area, resulting in little damage.  One of the tornadoes was on the ground for about 2 miles in Greene County.  The tornado damages garages, porches, and trees for the most part.  Several power lines were taken down as well.  A second tornado in Greene County caused minor house damage west of Jefferson.  Another stronger tornado touched down southeast of Collins in Story County.  Four out buildings were damages or destroyed and numerous trees were taken down. This tornado was on the ground for nearly 3 miles as it headed northeast of Collins.  The tornado lifted and another tornado formed in Marshall County shortly after the cell crossed the border.   A tornado touched down in northwest Lucas County and tracked for 2 miles northeast.  One farmstead had extensive damage with one machine shed destroyed and others damaged.  Three other tornadoes occurred,  One in Polk County east of Elkhart did minor damage.  Another tornado touched down northwest of State Center and caused F1 damage along its 3 mike long track.

Tornado in MARSHALL, IOWA
From 05-SEP-04 20:17:00 to 05-SEP-04 20:24:00 (CST)
Location: STATE CENTER
Tornado F-scale: F1
Property damage: 10K
Crop damage: 2K
Reported by: NWS EMPLOYEE(OFF DUTY)

Tornado tracked through rural areas of Marshall County west of State Center.

Tornado in POLK, IOWA
From 05-SEP-04 19:51:00 to 05-SEP-04 19:52:00 (CST)
Location: ELKHART
Tornado F-scale: F0
Property damage: 5K
Crop damage: 1K
Reported by: NWS STORM SURVEY

Tornado made a brief touchtown in open country.

Tornado in MARSHALL, IOWA
From 05-SEP-04 20:17:00 to 05-SEP-04 20:17:00 (CST)
Location: STATE CENTER
Tornado F-scale: F0
Property damage: 20K
Crop damage: 5K
Reported by: NWS STORM SURVEY

Tornado tracked across open country but did damage trees, sheds, and a grain bin.

Thunderstorm Wind in STORY, IOWA
From 05-SEP-04 20:14:00 to 05-SEP-04 20:14:00 (CST)
Location: COLO
Magnitude: 52 EG
Property damage: 2K
Reported by: AMATEUR RADIO

Tornado in STORY, IOWA
From 05-SEP-04 20:06:00 to 05-SEP-04 20:11:00 (CST)
Location: COLLINS
Tornado F-scale: F1
Property damage: 30K
Crop damage: 2K
Reported by: EMERGENCY MANAGER

Tornado damaged 4 outbuildings and downed trees.  Tornado tracked northeast and terminated 3 miles northeast of Collins.

Tornado in LUCAS, IOWA
From 05-SEP-04 19:48:00 to 05-SEP-04 19:51:00 (CST)
Location: LUCAS
Tornado F-scale: F0
Property damage: 75K
Crop damage: 5K
Reported by: NWS STORM SURVEY

Tornado touched down in northwest Lucas County and tracked northeast for about two miles.  Extensive damage was reported on one farm.

Tornado in GREENE, IOWA
From 05-SEP-04 17:04:00 to 05-SEP-04 17:10:00 (CST)
Location: JEFFERSON
Tornado F-scale: F1
Property damage: 50K
Crop damage: 10K
Reported by: LAW ENFORCEMENT

Small tornado caused garage, porch, and tree damage from about 310th Street and O Avenue to 290th Street and P avenue showing the most damage.  Damage in Rural areas was to trees and power poles.

Tornado in GREENE, IOWA
From 05-SEP-04 17:15:00 to 05-SEP-04 17:15:00 (CST)
Location: JEFFERSON
Tornado F-scale: F0
Crop damage: 1K
Reported by: EMERGENCY MANAGER

Brief touchdown in open country.

Tornado in HAMILTON, IOWA
From 05-SEP-04 18:15:00 to 05-SEP-04 18:15:00 (CST)
Location: WEBSTER CITY
Tornado F-scale: F0
Crop damage: 1K
Reported by: TRAINED SPOTTER

Brief touchdown in open country.

Tornado in WARREN, IOWA
From 05-SEP-04 18:52:00 to 05-SEP-04 18:52:00 (CST)
Location: NORWALK
Tornado F-scale: F0
Crop damage: 1K
Reported by: BROADCAST MEDIA

Brief touchdown in open country.

Thunderstorm Wind in WARREN, IOWA
From 05-SEP-04 20:00:00 to 05-SEP-04 20:02:00 (CST)
Location: LACONA
Magnitude: 52 EG
Property damage: 5K
Crop damage: 2K
Reported by: NWS STORM SURVEY