A mesoscale convective system intensified over the Lower Ohio Valley as it interacted with a moist and increasingly unstable atmosphere. The combination of daytime heating and an unstable southerly wind flow contributed to the intensification of the system, which exhibited bowing structures at times. Westerly winds of 40 to 45 knots in the mid levels of the atmosphere supported the acceleration of the bow echo across the region. Isolated wind damage accompanied the system.

Thunderstorm Wind in VANDERBURGH, INDIANA
From 27-JUN-11 11:40:00 to 27-JUN-11 11:40:00 (CST-6)
Location: SMYTHE
Magnitude: 65.00 EG
Crop damage: 0.00K
Reported by: NWS Storm Survey

A microburst containing peak winds estimated near 75 mph nearly levelled a large building. The building was constructed of wooden beams and sheet metal, similar to many external home garages only larger. At least one other smaller building was destroyed. Several tree limbs were blown down. There was minor damage to a couple of homes, including the loss of a few shingles. The microburst occurred just northwest of exit 10 on Interstate 164. The average path width was one-quarter mile. The length of the damage path was about one-half mile.

Thunderstorm Wind in SPENCER, INDIANA
From 27-JUN-11 12:57:00 to 27-JUN-11 13:00:00 (CST-6)
Location: EUREKA
Magnitude: 78.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A heat burst occurred in the wake of a line of thunderstorms. About two miles east of Hatfield on Route 66, a large fertilizer auger leg was blown down off a fertilizer storage building. The building sustained minor structural damage to a section of the roof, as well as some limited loss of shingles. Five empty fertilizer wagons were blown up to 100 feet. Several tree limbs were blown down. Peak winds were estimated near 90 mph. The damage area was only about one-quarter mile long and one-quarter mile wide. A heat burst is defined as a localized, sudden increase in surface temperature associated with a thunderstorm, shower, or mesoscale convective system. This heat burst occurred approximately an hour or less following an intense area of thunderstorms that moved through the area. Two witnesses outside during the heat burst experienced temperatures which they believed to be around 100 degrees. The extreme temperatures were said to have only lasted seconds before quickly falling. Heat bursts almost invariably form on the trailing edge of thunderstorm systems. Heat bursts are extremely rare, and this one was especially rare because most heat bursts occur at night. About three miles southeast of Eureka, a trained spotter observed debris in the air above a bending tree line to the south. The wind was accompanied by a roaring sound. This was likely the same heat burst or closely associated with the one near Hatfield.

Thunderstorm Wind in WARRICK, INDIANA
From 27-JUN-11 12:45:00 to 27-JUN-11 12:45:00 (CST-6)
Location: YANKEETOWN
Magnitude: 78.00 EG
Property damage: 40.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A two-ton delivery truck was blown over into a small trailer. A lawn tractor was overturned. Several mainly small trees were uprooted, and several large limbs were broken. A two-story home suffered considerable shingle loss. The peak winds were estimated near 90 mph. The microburst damage area was about 300 yards wide and one-half mile long.