Damaging winds were the primary type of severe weather as an extensive squall line crossed southern Illinois. Thunderstorms were organized into bowing line segments that  produced damaging winds as they moved rapidly east at 50 to 60 mph. The storms occurred along and ahead of a cold front that trailed south from a low pressure center near St. Louis. Isolated severe thunderstorm cells developed ahead of the quasi-linear convective system. Moderate instability existed ahead of the line of storms, with capes from 1500 to 2500 j/kg. Wind shear remained more than adequate for organization of the storms, with winds veering vertically in the lowest 3 km.

Hail in HARDIN, ILLINOIS
From 07-SEP-12 18:12:00 to 07-SEP-12 18:12:00 (CST-6)
Location: ELIZABETHTOWN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm Wind in SALINE, ILLINOIS
From 07-SEP-12 19:02:00 to 07-SEP-12 19:02:00 (CST-6)
Location: GALATIA
Magnitude: 52.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Three trees were down on Highway 34.

Thunderstorm Wind in JACKSON, ILLINOIS
From 07-SEP-12 18:23:00 to 07-SEP-12 18:23:00 (CST-6)
Location: MAKANDA
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several trees were blown down.

Thunderstorm Wind in PULASKI, ILLINOIS
From 07-SEP-12 19:42:00 to 07-SEP-12 19:42:00 (CST-6)
Location: MOUNDS
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Two trees were blown down.

Thunderstorm Wind in UNION, ILLINOIS
From 07-SEP-12 18:18:00 to 07-SEP-12 18:18:00 (CST-6)
Location: ANNA
Magnitude: 52.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Utility Company

A few trees were blown down, along with numerous tree limbs.

Thunderstorm Wind in JACKSON, ILLINOIS
From 07-SEP-12 18:22:00 to 07-SEP-12 18:22:00 (CST-6)
Location: MURPHYSBORO
Magnitude: 52.00 MG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: ASOS

Tree damage was reported in the cities of Carbondale and Murphysboro. A wind gust to 60 mph was measured at the automated observation site at the Carbondale airport. In Murphysboro, a downed tree took down a power line that landed on a house.

Thunderstorm Wind in SALINE, ILLINOIS
From 07-SEP-12 19:09:00 to 07-SEP-12 19:09:00 (CST-6)
Location: HARRISBURG
Magnitude: 56.00 EG
Property damage: 8.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several trees and power lines were blown down. Wind gusts were estimated near 65 mph.

Thunderstorm Wind in WHITE, ILLINOIS
From 07-SEP-12 19:35:00 to 07-SEP-12 19:35:00 (CST-6)
Location: CARMI MUNI ARPT
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

A wind gust to 61 mph was measured at the automated observation site at the Carmi airport.

Heavy Rain in PERRY, ILLINOIS
From 07-SEP-12 18:20:00 to 07-SEP-12 18:50:00 (CST-6)
Location: PINCKNEYVILLE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One inch of rain was measured in 30 minutes.

Thunderstorm Wind in WILLIAMSON, ILLINOIS
From 07-SEP-12 18:15:00 to 07-SEP-12 18:15:00 (CST-6)
Location: MARION
Magnitude: 61.00 EG
Property damage: 80.00K
Crop damage: 0.00K
Reported by: Trained Spotter

On the east edge of Marion near the fairgrounds, a roof was blown off a plumbing business. Metal roof debris was entangled in power lines. The plumbing business was in a large metal shed-type structure. Trees were blown down on a street on the south end of town. Numerous power outages were reported. Portable stop signs were placed at intersections where traffic lights were not functioning. A power pole fell on a car on Old Route 13. About 3,500 utility customers were without power at the peak of the storm.

Thunderstorm Wind in HAMILTON, ILLINOIS
From 07-SEP-12 19:15:00 to 07-SEP-12 19:15:00 (CST-6)
Location: MC LEANSBORO MUNI AR
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several trees were blown down, blocking Illinois Highway 142. State road crews were called out to clear the road.