During the afternoon and evening hours on June 21st a combination of old thunderstorm activity that moved in from upstream of Indiana, along with new development behind the previous activity occurred as a result of upper level atmospheric support and ample surface heating.  This led to a very to extremely unstable air mass...with MLCAPES exceeding 3500 j/kg.
By early evening discrete cells developed along a west to east oriented boundary that extended roughly from near the Missouri/Iowa border eastward through central Illinois and then to just north of Lafayette, Indiana.  Radar data showed several of these storm cells having supercellular structure/rotation as they encountered enhanced low level helicity (most simply put, helicity is the amount of spin to a parcel of air) along the boundary.  Upstream wind profile data at Davenport, Iowa showed favorable veering of wind with height for storm rotation. Upper air data from the 00z (7 PM EST) sounding from the Central Illinois National Weather Service office showed a low lifted condensation level of 3000 ft and steep low level lapse rates, which lent support to the storms. Storms forming upstream of Indiana moved into the state as the day progressed.

Thunderstorm Wind in HANCOCK, INDIANA
From 22-JUN-10 03:55:00 to 22-JUN-10 03:55:00 (EST-5)
Location: WOODBURY
Magnitude: 55.00 EG
Property damage: 1.50K
Reported by: Amateur Radio

Thunderstorm winds blew down a large tree and power lines in the vicinity of Carroll Road and 96th Street.  The tree had approximately a 4-foot diameter base.

Flood in HAMILTON, INDIANA
From 22-JUN-10 06:19:00 to 22-JUN-10 08:19:00 (EST-5)
Location: FISHERS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Heavy rainfall caused minor flooding of Interstate 69 near Exit 3.

Flash Flood in HAMILTON, INDIANA
From 22-JUN-10 06:30:00 to 22-JUN-10 08:30:00 (EST-5)
Location: FISHERS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rainfall caused significant ponding of water over the west bound lane of 116th Street east of Hague and Cumberland Roads.  An estimated 4 to 6 inches of water was present.

Flood in MORGAN, INDIANA
From 22-JUN-10 08:00:00 to 23-JUN-10 06:00:00 (EST-5)
Location: MOORESVILLE
Flood cause: Dam / Levee Break
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A dam break upstream, along with heavy rainfall, caused flooding along the East Fork White Lick Creek in the Mooresville, Indiana area. As of mid to late afternoon on June 22nd water was up to business properties and crossing Old State Road 67.  Property damage estimate is greatly estimated.

Lightning in HAMILTON, INDIANA
From 22-JUN-10 00:24:00 to 22-JUN-10 00:24:00 (EST-5)
Location: HOME PLACE
Property damage: 3.50M
Reported by: Newspaper

Newspaper and broadcast media reported a lightning strike was the suspected cause of a fire of a shopping strip in western Carmel, Indiana. Firefighters think lightning struck the El Rodeo restaurant, located in the 12-unit Weston Shoppes, and quickly spread across the shopping center. The strip mall owner said continuing lightning strikes prevented firefighters from hosing the flames from their ladder trucks, hampering their efforts to save the building. Damage estimates, not including each store's inventory, could be between 3 and 4 million dollars. Firefighters were still on the scene 8 1/2 hours later.

Flash Flood in HENDRICKS, INDIANA
From 22-JUN-10 07:22:00 to 22-JUN-10 09:22:00 (EST-5)
Location: PLAINFIELD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Plainfield Police evacuated 25 people on a voluntary basis from the Crystal Bay neighborhood due to flooding.  Several roads in the nearby area were flooded and closed to traffic:  Sugar Grove (700 E), Township Line Road between Dan Jones and Smith Road, 300 South between Vestal and Center Street, South Center Street between Hadley Road and I-70, 2600 East Main Street, and Vestal/800 East. Time of event is estimated.

Flash Flood in HENDRICKS, INDIANA
From 22-JUN-10 07:22:00 to 22-JUN-10 09:22:00 (EST-5)
Location: AVON
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 3.00K
Reported by: Law Enforcement

Heavy rainfall draining into White Lick Creek caused the creek to overflow. A mobile home park near 600 East and 100 North was in the process of evacuation due to concern of a possible dam break.  Damage estimate is greatly estimated.

Flash Flood in HENDRICKS, INDIANA
From 22-JUN-10 08:15:00 to 22-JUN-10 11:15:00 (EST-5)
Location: TILDEN
Flood cause: Dam / Levee Break
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Newspaper

A privately owned earthen dam was breached at Indianhead Lake as a result of very heavy rainfall runoff. About 40 homes and 16 mobile homes were evacuated, but by afternoon most of the residents were allowed to return. Officials decided to drain the 4-acre lake behind the Indianhead dam as a result of the damage and in case additional rainfall/runoff occurred that might produce further damage and downstream flooding. Damage estimates are greatly estimated. Floodwaters topped nearby Jeto Lake's dam but it held.

Flash Flood in HENDRICKS, INDIANA
From 22-JUN-10 07:22:00 to 22-JUN-10 09:22:00 (EST-5)
Location: SPEEDWAY ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Low-lying portions of Indiana 136 and Interstate 74 were briefly flooded. Time of event is estimated.

Flash Flood in CLINTON, INDIANA
From 22-JUN-10 07:00:00 to 22-JUN-10 12:00:00 (EST-5)
Location: EDNA MILLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

The entire town of Edna Mills was evacuated due to high water.  School buses were brought in at the east end of town for evacuees, to be taken east to Rossville, Indiana. Indiana Department of Natural Resources brought in boats to get to the homes that were surrounded by water at time of evacuation. The decision to evacuate was made at 9 AM on the 22nd.  Time of event is estimated.  No damages are known.

Flash Flood in MARION, INDIANA
From 22-JUN-10 00:40:00 to 22-JUN-10 02:40:00 (EST-5)
Location: HOMECROFT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Rainfall runoff was reported to be flowing over the road at U. S. 31 and Stop 12.

Hail in HENDRICKS, INDIANA
From 22-JUN-10 00:30:00 to 22-JUN-10 00:32:00 (EST-5)
Location: SPEEDWAY ARPT
Magnitude: 0.88 
Reported by: Amateur Radio

Thunderstorm Wind in TIPPECANOE, INDIANA
From 22-JUN-10 00:40:00 to 22-JUN-10 00:40:00 (EST-5)
Location: WEST LAFAYETTE
Magnitude: 53.00 MG
Reported by: Broadcast Media

Flood in MARION, INDIANA
From 22-JUN-10 00:44:00 to 22-JUN-10 02:44:00 (EST-5)
Location: INDIANAPOLIS SPEEDWA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A creek was reported to be badly overflowing into a backyard near the intersection of West 21st and North Raceway Road.

Hail in TIPPECANOE, INDIANA
From 22-JUN-10 00:50:00 to 22-JUN-10 00:52:00 (EST-5)
Location: WEST LAFAYETTE
Magnitude: 1.00 
Reported by: Trained Spotter

Thunderstorm Wind in HAMILTON, INDIANA
From 22-JUN-10 02:18:00 to 22-JUN-10 02:18:00 (EST-5)
Location: FISHERS
Magnitude: 52.00 EG
Reported by: Amateur Radio

Thunderstorm winds blew at an estimated 50 to 60 MPH at/near the intersection of 131st and Hazel Dell Parkway.  Torrential rainfall accompanied these winds.

Thunderstorm Wind in MARION, INDIANA
From 22-JUN-10 02:30:00 to 22-JUN-10 02:30:00 (EST-5)
Location: INDIANAPOLIS
Magnitude: 50.00 MG
Reported by: Emergency Manager

Thunderstorm Wind in HANCOCK, INDIANA
From 22-JUN-10 02:34:00 to 22-JUN-10 02:34:00 (EST-5)
Location: WOODBURY
Magnitude: 66.00 MG
Reported by: Trained Spotter

Thunderstorm winds were clocked at 46 MPH with gusts to 76 MPH at the intersection of 96th Street and Olio Road in McCordsville, IN....just northeast of Indianapolis.

Thunderstorm Wind in MARION, INDIANA
From 22-JUN-10 02:34:00 to 22-JUN-10 02:34:00 (EST-5)
Location: OAKLANDON
Magnitude: 52.00 EG
Reported by: Amateur Radio

Thunderstorm winds blew down a healthy tree/tree limb at its 10-inch diameter base.

Thunderstorm Wind in MARION, INDIANA
From 22-JUN-10 02:35:00 to 22-JUN-10 02:35:00 (EST-5)
Location: IND BROOKSIDE ARPT
Magnitude: 52.00 EG
Reported by: Amateur Radio

Thunderstorm winds blew down power lines at the intersection of 75th Street and State Road 67.