Two distinct boundaries were in place across Iowa.  A cold front had slipped into the northwest part of the state and nearly bisected the state by the early evening hours.  Meanwhile, an east-northeast to west-southwest boundary was in place across the central part of the state.  The second boundary was left in place by the convection that occurred earlier in the day.  The airmass remained quite unstable during the evening with dew point temperatures in the mid 60s to around 70.  Colder air continued to slip into the state aloft with the freezing level falling just below 12,000 feet by the early evening.  Another round of thunderstorms fired to the southwest of Iowa and moved into the state during the evening.  Strong winds of 40 kts or more at the 850 mb level pushed over the top of the two boundaries over the state.  Thunderstorms developed rapidly.  This round of thunderstorms produced high winds and some hail.  Though hail was not the predominant form of severe weather with this round, most of the storms did produce at least pea to marble size hail.  Hail of nickle to near one inch in diameter was reported in Adair and Decatur Counties.  The main severe activity this time around was high winds as the storms developed into a series of small bow echoes.  High winds developed in southwest and central Iowa during the early evening.   In Adams County, high winds two 40,000 bushel grain bins were destroyed and blown across the field two miles by downburst winds east of Corning.  North of Corning high winds destroyed a grain elevator, a barn, and damaged several grain bins.  Losses were placed at $250.000.  The storms raced northeast and so did the high winds.  Most of the storms produced winds of 60 MPH or higher.    Winds of 70 MPH ripped through Warren County as one bow element moved east rapidly to the south of the Des Moines Metropolitan area.  The winds flipped over a semi tractor-trailer truck on Interstate 35 just south of Des Moines, west of Cumming.    As the bow echo advanced east, high winds damaged a trailer home in Carlisle, while the roof was blown off of an apartment building.  This was not the only strong bow echo.  Another bow segment moved into Marshall and Jasper Counties.  Winds of 65 to 75 MPH were common in these storms.  Windows were blown out of a house in Jasper County at Newton.  Winds of 70 MPH advanced east into Poweshiek County as well.  A very strong storm moved into Appanoose County during the late evening hours and tore through the county causing considerable damage.  Several mobile homes were destroyed in the town of Centerville by winds near 85 MPH.  One person was injured and was trapped in the debris.  Fortunately, the injury was minor.  A semi tractor-trailer was overturned on the north side of Centerville by the high winds.  A short time before, the storms moved through the Numa area with the high winds completely destroying a farm house there.  It appears the winds from this event were likely a combination of microburst as well as the bow echo itself.  Farther northeast, the main area of thunderstorms that moved through central Iowa passed through the Waterloo area.  Considerable damage was reported in the Waterloo and Cedar Falls areas.

Thunderstorm Wind in ADAIR, IOWA
From 07-SEP-01 19:10:00 to 07-SEP-01 19:10:00 (CST)
Location: ORIENT
Magnitude: 52 E
Property damage: 3K
Reported by: UNKNOWN

Thunderstorm Wind in ADAIR, IOWA
From 07-SEP-01 19:15:00 to 07-SEP-01 19:15:00 (CST)
Location: ORIENT
Magnitude: 57 E
Property damage: 10K
Crop damage: 1K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 19:57:00 to 07-SEP-01 19:57:00 (CST)
Location: MARTENSDALE
Magnitude: 61 E
Property damage: 15K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 19:57:00 to 07-SEP-01 19:57:00 (CST)
Location: ST MARYS
Magnitude: 52 E
Property damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in ADAIR, IOWA
From 07-SEP-01 19:31:00 to 07-SEP-01 19:31:00 (CST)
Location: GREENFIELD
Magnitude: 52 E
Property damage: 3K
Reported by: AMATEUR RADIO

Hail in DECATUR, IOWA
From 07-SEP-01 19:32:00 to 07-SEP-01 19:32:00 (CST)
Location: GRAND RIVER
Magnitude: 1.00 
Property damage: 4K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DECATUR, IOWA
From 07-SEP-01 19:32:00 to 07-SEP-01 19:32:00 (CST)
Location: GRAND RIVER
Magnitude: 52 E
Property damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MADISON, IOWA
From 07-SEP-01 19:41:00 to 07-SEP-01 19:41:00 (CST)
Location: WINTERSET
Magnitude: 52 E
Property damage: 3K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in MADISON, IOWA
From 07-SEP-01 19:45:00 to 07-SEP-01 19:45:00 (CST)
Location: WINTERSET
Magnitude: 52 E
Property damage: 3K
Reported by: AMATEUR RADIO

Thunderstorm Wind in MADISON, IOWA
From 07-SEP-01 19:47:00 to 07-SEP-01 19:47:00 (CST)
Location: WINTERSET
Magnitude: 52 E
Property damage: 10K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in DALLAS, IOWA
From 07-SEP-01 19:51:00 to 07-SEP-01 19:51:00 (CST)
Location: ADEL
Magnitude: 52 E
Property damage: 5K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in WAYNE, IOWA
From 07-SEP-01 21:30:00 to 07-SEP-01 21:30:00 (CST)
Location: SEYMOUR
Magnitude: 61 E
Property damage: 25K
Crop damage: 5K
Reported by: NEWSPAPER

Hail in ADAIR, IOWA
From 07-SEP-01 19:17:00 to 07-SEP-01 19:17:00 (CST)
Location: ORIENT
Magnitude: 0.88 
Property damage: 1K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 20:22:00 to 07-SEP-01 20:22:00 (CST)
Location: CARLISLE
Magnitude: 75 E
Property damage: 50K
Crop damage: 10K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in JASPER, IOWA
From 07-SEP-01 20:28:00 to 07-SEP-01 20:28:00 (CST)
Location: PRAIRIE CITY
Magnitude: 52 E
Property damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in MARSHALL, IOWA
From 07-SEP-01 20:33:00 to 07-SEP-01 20:33:00 (CST)
Location: STATE CENTER
Magnitude: 57 E
Property damage: 10K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in JASPER, IOWA
From 07-SEP-01 20:40:00 to 07-SEP-01 20:40:00 (CST)
Location: PRAIRIE CITY
Magnitude: 52 E
Property damage: 3K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in JASPER, IOWA
From 07-SEP-01 20:46:00 to 07-SEP-01 20:46:00 (CST)
Location: NEWTON
Magnitude: 61 E
Property damage: 15K
Crop damage: 4K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in POWESHIEK, IOWA
From 07-SEP-01 21:39:00 to 07-SEP-01 21:39:00 (CST)
Location: BROOKLYN
Magnitude: 61 E
Property damage: 15K
Crop damage: 4K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in APPANOOSE, IOWA
From 07-SEP-01 21:40:00 to 07-SEP-01 21:40:00 (CST)
Location: NUMA
Magnitude: 78 E
Property damage: 100K
Crop damage: 20K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in TAYLOR, IOWA
From 07-SEP-01 18:45:00 to 07-SEP-01 18:45:00 (CST)
Location: LENOX
Magnitude: 57 E
Property damage: 15K
Crop damage: 2K
Reported by: NEWSPAPER

Thunderstorm Wind in APPANOOSE, IOWA
From 07-SEP-01 21:45:00 to 07-SEP-01 21:45:00 (CST)
Location: CENTERVILLE
Magnitude: 75 E
Property damage: 100K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in BLACK HAWK, IOWA
From 07-SEP-01 21:50:00 to 07-SEP-01 21:50:00 (CST)
Location: CEDAR FALLS
Magnitude: 65 E
Property damage: 25K
Crop damage: 5K
Reported by: AMATEUR RADIO

Thunderstorm Wind in BLACK HAWK, IOWA
From 07-SEP-01 21:54:00 to 07-SEP-01 21:54:00 (CST)
Location: WATERLOO
Magnitude: 52 E
Property damage: 10K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in BLACK HAWK, IOWA
From 07-SEP-01 21:55:00 to 07-SEP-01 21:55:00 (CST)
Location: WATERLOO
Magnitude: 57 E
Property damage: 50K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in ADAMS, IOWA
From 07-SEP-01 18:35:00 to 07-SEP-01 18:35:00 (CST)
Location: CORNING
Magnitude: 70 E
Property damage: 150K
Crop damage: 20K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in ADAMS, IOWA
From 07-SEP-01 18:52:00 to 07-SEP-01 18:52:00 (CST)
Location: CORNING
Magnitude: 65 E
Property damage: 250K
Crop damage: 25K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in POLK, IOWA
From 07-SEP-01 20:10:00 to 07-SEP-01 20:10:00 (CST)
Location: DES MOINES ARPT
Magnitude: 52 M
Property damage: 3K
Reported by: AWOS,ASOS,MESONET,ETC

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 20:10:00 to 07-SEP-01 20:10:00 (CST)
Location: INDIANOLA
Magnitude: 57 E
Property damage: 10K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in POLK, IOWA
From 07-SEP-01 20:20:00 to 07-SEP-01 20:20:00 (CST)
Location: DES MOINES
Magnitude: 54 E
Property damage: 10K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 20:20:00 to 07-SEP-01 20:20:00 (CST)
Location: CARLISLE
Magnitude: 57 E
Property damage: 15K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in WARREN, IOWA
From 07-SEP-01 19:57:00 to 07-SEP-01 19:57:00 (CST)
Location: CUMMING
Magnitude: 61 E
Property damage: 25K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in CLARKE, IOWA
From 07-SEP-01 20:00:00 to 07-SEP-01 20:00:00 (CST)
Location: OSCEOLA
Magnitude: 52 E
Property damage: 3K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in CLARKE, IOWA
From 07-SEP-01 20:10:00 to 07-SEP-01 20:10:00 (CST)
Location: OSCEOLA
Magnitude: 61 E
Property damage: 25K
Crop damage: 3K
Reported by: BROADCAST MEDIA