A very unstable airmass remained in place across Iowa on the evening of the 6th with an east-west boundary lying across the mid section of the state.  CAPE rose to around 4000 J/kg by late afternoon as afternoon highs reached the upper 80s to low 90s, and dew point temperatures were in the mid 70s to low 80s.  The freezing level was very high, between 16,000 and 16,500 feet, reducing the threat of hail even though the CAPE in the hail layer, -10 to -30 C. layer, was in the 500 to 700 J/kg range.  Downdraft cape was significant at around 1200 J/kg.  The lifted index fell to between -4 and -8 C. by late afternoon with an effective shear of 35 to 45 kts across the area.  LCL values were between 750 and 1000 meters.  There was copious amounts of moisture in the atmosphere with between 1.7 to over 2 inches of precipitable water.  Heavy rainfall was the most significant threat.  Heavy rainfall of around 3 inches occurred in Cass County.  The town of Griswold recorded 3.6 inches of rain.  This resulted in flash flooding in the Griswold area.  Reports of 4 feet of water running over the highways were received.  Two to three inches of rain fell in Audubon County, with water running over Highway 173 southeast of Kimballton.  Severe weather was spotty.  Thunderstorms winds downed trees in Cass County from Griswold to about 3 miles northeast of Griswold.  There was also a 60 MPH wind reported northwest of Griswold.  Later in the evening, the thunderstorms moved east into central Iowa.  One storm produced a microburst northwest of Van Meter in Dallas County.  The winds blew in a garage wall and tossed the roof down on a nearby car.  An uninstalled modular home was demolished along with several trees being downed.  As the storms developed east into the metro Des Moines area, lightning struck a house in Urbandale starting it on fire.  There were no injuries.  In addition, lightning struck a garage in Denison, setting it on fire.  The garage was destroyed along with numerous vehicles inside.  Later on, thunderstorms moved across southwest Iowa.  One of the storms struck a chicken barn in Taylor County.  The lightning bolt blew a whole in the electrical box and set the chicken barn on fire.  The barn was destroyed, but fortunately it was empty at the time.  The lightning also knocked out the power at a nearby hog building, killing 700 young pigs due to lack of ventilation when the fans went out.

Flash Flood in CASS, IOWA
From 06-AUG-07 19:45:00 to 07-AUG-07 01:00:00 (CST-6)
Location: GRISWOLD
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 25.00K
Reported by: Law Enforcement

Flash Flood in AUDUBON, IOWA
From 06-AUG-07 22:00:00 to 07-AUG-07 00:40:00 (CST-6)
Location: IMBALLTON
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Thunderstorm Wind in CASS, IOWA
From 06-AUG-07 19:50:00 to 06-AUG-07 19:50:00 (CST-6)
Location: GRISWOLD
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CASS, IOWA
From 06-AUG-07 19:57:00 to 06-AUG-07 19:57:00 (CST-6)
Location: LEWIS
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorm Wind in CASS, IOWA
From 06-AUG-07 19:45:00 to 06-AUG-07 19:45:00 (CST-6)
Location: GRISWOLD
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lightning in POLK, IOWA
From 07-AUG-07 00:30:00 to 07-AUG-07 00:30:00 (CST-6)
Location: URBANDALE
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm Wind in DALLAS, IOWA
From 06-AUG-07 22:57:00 to 06-AUG-07 22:57:00 (CST-6)
Location: VAN METER
Magnitude: 80.00 EG
Property damage: 75.00K
Crop damage: 5.00K
Reported by: Emergency Manager

Lightning in CRAWFORD, IOWA
From 07-AUG-07 01:04:00 to 07-AUG-07 01:04:00 (CST-6)
Location: DENISON
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Newspaper

Lightning in TAYLOR, IOWA
From 07-AUG-07 04:35:00 to 07-AUG-07 04:35:00 (CST-6)
Location: CLEARFIELD
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Newspaper