A cold front moved into the state from the northwest during the day on the 31st.  The airmass became unstable in front of it with a considerable push of deep moisture.  Precipitable water values increased to 2 to 2.4 inches by afternoon.  CAPE increased to 2500 to 4000 J/kg as afternoon temperatures climbed into the mid to upper 80s, with dewpoint readings in the low to middle 70s.  The lifted index fell to -5 to -7 C.  The atmosphere was not strongly sheared with 25 to 35 kts of effective shear available.  CAPE in the -10 to -30 C layer of the atmosphere was between 600 and 800 J/kg.  Downdraft CAPE was in the 1000-1400 J/kg range.  A squall line developed ahead of the cold front and became marginally severe.  Many of the storms produced small hail and gusty winds.  A few locations reported winds in excess of 60 MPH, with the the highest winds reported of 64 MPH in Carroll County in Templeton.  High winds from thunderstorms moving into Winnebago County downed trees in a city park in Buffalo Center.  Winds estimated near 80 MPH snapped the top off of a power pole in Buffalo Center and also caused considerable tree damage and out building damage in the area.  Heavy rainfall was an issue with the storms given the high precipitable water values.  Three inches of rain fell in 50 minutes southeast of Madrid in Boone County, with reports of around 4 inches for storm total in the Ames area.  In Emmet County, 2.65 inches of rain fell in a little over an hour in Ringsted.  Fortunately, it has been quite dry for the previous 10 days.  The rains did not cause flash flooding, but did result in some urban flooding.  A 15 year old girl was struck by lightning in Leon as the thunderstorms passed.  She was walking across a parking lot and lightning struck just as she reached for the door handle of her car.  She was taken to hospital and remained overnight, however there were no detectable injuries beyond memory loss of the event.

Thunderstorm Wind in CARROLL, IOWA
From 31-AUG-10 18:18:00 to 31-AUG-10 18:18:00 (CST-6)
Location: TEMPLETON
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

No damage was reported.

Heavy Rain in EMMET, IOWA
From 31-AUG-10 14:00:00 to 31-AUG-10 15:21:00 (CST-6)
Location: RINGSTED
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Rainfall of 2.65 inches since 1400 CST.

Heavy Rain in BOONE, IOWA
From 31-AUG-10 19:19:00 to 31-AUG-10 20:09:00 (CST-6)
Location: MADRID
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Three inches of rain fell in the past 50 minutes.

Lightning in DECATUR, IOWA
From 31-AUG-10 20:20:00 to 31-AUG-10 20:20:00 (CST-6)
Location: LEON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A 15 year old girl was struck by lightning.

Thunderstorm Wind in WINNEBAGO, IOWA
From 31-AUG-10 15:32:00 to 31-AUG-10 15:32:00 (CST-6)
Location: BUFFALO CENTER
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Thunderstorms produced wind gusts of around 60 MPH, toppling several trees in the city park.

Thunderstorm Wind in BOONE, IOWA
From 31-AUG-10 19:22:00 to 31-AUG-10 19:22:00 (CST-6)
Location: BOXHOLM
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power line reported down in Boxholm.

Thunderstorm Wind in GREENE, IOWA
From 31-AUG-10 18:52:00 to 31-AUG-10 18:52:00 (CST-6)
Location: FARLIN
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 10.00K
Reported by: Fire Department/Rescue

Winds approaching 60 MPH were estimated.  Limbs of up to 6 inch in diameter were broken with pea to nickle size hail.

Hail in GREENE, IOWA
From 31-AUG-10 18:52:00 to 31-AUG-10 18:52:00 (CST-6)
Location: FARLIN
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Pea to nickel size hail.

Thunderstorm Wind in WINNEBAGO, IOWA
From 31-AUG-10 15:40:00 to 31-AUG-10 15:40:00 (CST-6)
Location: BUFFALO CENTER
Magnitude: 70.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Newspaper

High winds snapped the top off of a power pole.

Heavy Rain in STORY, IOWA
From 31-AUG-10 20:49:00 to 31-AUG-10 20:49:00 (CST-6)
Location: SLATER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Rainfall storm total so far was 3.85 inches.

Thunderstorm Wind in TAMA, IOWA
From 31-AUG-10 20:45:00 to 31-AUG-10 20:45:00 (CST-6)
Location: TAMA
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees and power lines were down in Tama and Toledo.