A quasi-stationary front was located south of Iowa as an upper level shortwave advanced across the area in strong westerly flow aloft.  The atmosphere was somewhat unstable, albeit the instability was elevated in nature.  Available CAPE was in the 1000 to 2000 J/kg range with lifted indices of -3 to -5 C.  Moisture had pooled over the area with precipitable water values in the 1.3 to 1.7 inch range.  The freezing level was quite high for mid September at between 14,000 and 14,500 feet.  Significant shear was present in the atmosphere with 50 to 60 kts of effective shear present.  Other severe parameters were not all that strong.  Downdraft CAPE was less than 500 J/kg and the hail index showed 300 to 500 J/kg in the -10 to -30 C layer of the atmosphere.  The LCL was under 500 meters, however a strong inversion was present.  Thunderstorms developed in the evening and produced hail and heavy rain quite easily.  The cold surface temperatures, in the upper 40s to low 50s, helped maintain the hail size from these storms and overcame the high freezing level.  Storms in southwest Iowa produced the largest hail with golf ball size hail reported west of Bedford, and tennis ball size hail reported in the town of Bedford in Taylor County.  Hail up to three inches in diameter fell in Cass County south of Cumberland.  Storms farther east produced marginal hail with reports of nickel to quarter size hail received in central Iowa.  Several supercells moved across Taylor, Cass, Union, Adams, and Ringgold Counties through the night.  Reports of ping pong to golf ball size hail were numerous with these cells.  One of the storms intensified as it moved through the Mt Ayr area.  The storm dropped tennis ball size hail for about 10 minutes across the town, resulting in widespread damage to vehicles and buildings.  Insurance claims from the town were near $10 million.  The thunderstorms produced very heavy rainfall with rainfall rates in excess of 2 inches per hour at times.  The heaviest rainfall occurred across southern Cass into northern Adams Counties, and extended east into Union County.  The storms subsequently moved farther southeast with heavy rainfall pushing into Ringgold and parts of Decatur Counties.  The band was about 20 miles wide and produced general rainfall of 2 to 4 inches.  Flash flooding was reported with numerous roads closed by flowing water as 4 to 6 inches of rain fell in that area in under 2 hours.  Spotty reports of 4 to 8 inches of rainfall were received.  Flash flooding took place near Delphos in Ringgold County with 6 inches of flowing water over County Road J43.  Flash flooding was also reported in eastern Adams County along U.S. Highway 34.  Lightning caused a house fire in Ankeny as the leading edge of the morning storms moved into central Iowa.  Firefighters were dispatched to the house at 1530 CST Saturday afternoon. Neighbors had called 911 to report fire and smoke coming from the home's roof.  Flames were coming out the vents when firefighters arrived.

Flash Flood in UNION, IOWA
From 19-SEP-10 00:39:00 to 19-SEP-10 05:30:00 (CST-6)
Location: CROMWELL
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 25.00K
Reported by: Law Enforcement

Numerous roads flooded from Creston west to the county line.  Rainfall reported of 4 to 6 inches.

Hail in TAYLOR, IOWA
From 18-SEP-10 21:53:00 to 18-SEP-10 21:53:00 (CST-6)
Location: BEDFORD
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Law Enforcement

Reported on Highway 2.

Hail in POLK, IOWA
From 18-SEP-10 22:08:00 to 18-SEP-10 22:08:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 18-SEP-10 22:10:00 to 18-SEP-10 22:10:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CASS, IOWA
From 18-SEP-10 22:16:00 to 18-SEP-10 22:16:00 (CST-6)
Location: MASSENA SWAIN ARPT
Magnitude: 3.00 
Property damage: 25.00K
Crop damage: 50.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 18-SEP-10 22:16:00 to 18-SEP-10 22:16:00 (CST-6)
Location: DODGE FLD ARPT
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in TAYLOR, IOWA
From 18-SEP-10 22:17:00 to 18-SEP-10 22:17:00 (CST-6)
Location: BEDFORD
Magnitude: 2.50 
Property damage: 50.00K
Crop damage: 25.00K
Reported by: COOP Observer

Hail ranged from one half inch to two and one half inches in diameter.

Hail in RINGGOLD, IOWA
From 18-SEP-10 23:40:00 to 18-SEP-10 23:40:00 (CST-6)
Location: MT AYR
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 10.00K
Reported by: Law Enforcement

Flash Flood in RINGGOLD, IOWA
From 19-SEP-10 03:16:00 to 19-SEP-10 06:00:00 (CST-6)
Location: DELPHOS
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Up to 6 inches of water was flowing over County Road J43 near Delphos.

Hail in RINGGOLD, IOWA
From 18-SEP-10 23:36:00 to 18-SEP-10 23:36:00 (CST-6)
Location: MT AYR
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Nickel to golf ball size hail reported in town.

Hail in RINGGOLD, IOWA
From 18-SEP-10 23:45:00 to 18-SEP-10 23:45:00 (CST-6)
Location: MT AYR
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Spotter also reports 6.97 inches of rainfall along with the hail.

Hail in TAYLOR, IOWA
From 18-SEP-10 21:10:00 to 18-SEP-10 21:10:00 (CST-6)
Location: NEW MARKET
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Hail in TAYLOR, IOWA
From 18-SEP-10 21:10:00 to 18-SEP-10 21:10:00 (CST-6)
Location: NEW MARKET
Magnitude: 1.25 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in JASPER, IOWA
From 18-SEP-10 22:50:00 to 18-SEP-10 22:50:00 (CST-6)
Location: METZ
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 25.00K
Reported by: Public

Hail in ADAMS, IOWA
From 18-SEP-10 23:03:00 to 18-SEP-10 23:03:00 (CST-6)
Location: MT ETNA
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Penny to quarter size hail reported.

Hail in RINGGOLD, IOWA
From 18-SEP-10 23:21:00 to 18-SEP-10 23:21:00 (CST-6)
Location: DELPHOS
Magnitude: 1.75 
Property damage: 20.00K
Crop damage: 25.00K
Reported by: Public

Golf ball size hail with damage to vehicle and siding on the east side of a home.

Hail in ADAMS, IOWA
From 18-SEP-10 23:30:00 to 18-SEP-10 23:30:00 (CST-6)
Location: PRESCOTT
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 25.00K
Reported by: Public

Mostly pea size hail with largest up to the size of quarters.  Rainfall was 5.8 inches for the storm.

Hail in CASS, IOWA
From 19-SEP-10 00:36:00 to 19-SEP-10 00:36:00 (CST-6)
Location: GRISWOLD
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Quarter to ping pong ball size hail reported by a trained spotter.

Hail in ADAMS, IOWA
From 19-SEP-10 01:40:00 to 19-SEP-10 01:40:00 (CST-6)
Location: CARBON
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 25.00K
Reported by: Public

Hail in TAYLOR, IOWA
From 19-SEP-10 02:49:00 to 19-SEP-10 02:49:00 (CST-6)
Location: CONWAY
Magnitude: 1.75 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lightning in POLK, IOWA
From 18-SEP-10 15:30:00 to 18-SEP-10 15:30:00 (CST-6)
Location: ORALABOR
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash Flood in ADAMS, IOWA
From 19-SEP-10 02:29:00 to 19-SEP-10 05:00:00 (CST-6)
Location: PRESCOTT
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Newspaper

Hail in RINGGOLD, IOWA
From 18-SEP-10 23:35:00 to 18-SEP-10 23:45:00 (CST-6)
Location: MT AYR
Magnitude: 2.00 
Property damage: 10.00M
Crop damage: 0.00K
Reported by: Newspaper

Widespread property damage in Mt Ayr to both vehicles and buildings was reported.