A squall line with embedded sustained supercells crossed southern Illinois. The embedded supercells raced east-northeast at 60 to 70 mph, while the line moved southeast at a slower rate. The storms strengthened as they encountered richer low-level moisture, with surface dew points around 60 degrees spreading rapidly north-northeastward up the Mississippi Valley. Intense low to mid-level wind fields maintained the intensity of tornadic storms despite weak instability due to lack of solar heating. A south-southwesterly low level jet from 60 to 70 knots veered to west-southwest around 75 knots at 500 mb.

Tornado in SALINE, ILLINOIS
From 29-FEB-12 04:51:00 to 29-FEB-12 05:04:00 (CST-6)
Location: CARRIERS MILLS
Tornado F-scale: EF4
Property damage: 2.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado touched down about a mile north of Carrier Mills, then moved east-northeast through Harrisburg. The violent tornado produced a swath of devastation in south and southeast parts of Harrisburg. In Harrisburg, over 200 homes and about 25 businesses were heavily damaged or destroyed. The damage was in residential neighborhoods in the far south and southeast sections of Harrisburg. The commercial strip along U.S. Highway 45 in the south part of the city was directly impacted. A strip mall on the east side of U.S. Route 45 was destroyed. The tornado struck the Harrisburg medical center and surrounding residences on the southeast side of town. At least ten homes or other buildings were levelled, with several home structures displaced from their foundations. The neighborhood with the levelled homes and fatalities was adjacent to the destroyed strip mall. The tornado proceeded across Illinois Route 13 a few miles east of Harrisburg, destroying a farm house and a business. Hundreds of large trees were snapped or uprooted, along with many downed power lines. Peak winds were estimated near 180 mph based on numerous levelled and displaced homes. The average path width was 275 yards. The tornado continued into Gallatin County shortly after crossing Highway 142.

Tornado in MASSAC, ILLINOIS
From 29-FEB-12 05:35:00 to 29-FEB-12 05:39:00 (CST-6)
Location: METROPOLIS MUNI ARPT
Tornado F-scale: EF2
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado crossed the Ohio River from McCracken County, Kentucky. The tornado crossed U.S. Highway 45 before it lifted near the airport. Trees were uprooted and snapped. Barns and sheds were damaged or destroyed. The average path width was 125 yards. Peak winds were estimated near 120 mph.

Hail in JACKSON, ILLINOIS
From 29-FEB-12 04:22:00 to 29-FEB-12 04:22:00 (CST-6)
Location: BOSKYDELL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in WILLIAMSON, ILLINOIS
From 29-FEB-12 04:40:00 to 29-FEB-12 04:40:00 (CST-6)
Location: HUDGENS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in WILLIAMSON, ILLINOIS
From 29-FEB-12 04:20:00 to 29-FEB-12 04:20:00 (CST-6)
Location: WOLF CREEK
Magnitude: 87.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A downburst averaging 1/2 mile wide resulted in thousands of trees being snapped or uprooted in the Devil's Kitchen Lake area, around and east of the Giant City State Park area. Peak winds were estimated near 100 mph.

Tornado in JACKSON, ILLINOIS
From 29-FEB-12 04:18:00 to 29-FEB-12 04:20:00 (CST-6)
Location: MAKANDA
Tornado F-scale: EF2
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado passed into southeast Jackson County from Union County. The tornado was only on the ground for a short time in Jackson County before it lifted. The damage path ended in Giant City State Park. Thousands of trees were snapped or uprooted. Barns and grain bins were destroyed, along with downed power lines. Peak winds were estimated near 115 mph. The average path width was 250 yards.

Thunderstorm Wind in JACKSON, ILLINOIS
From 29-FEB-12 04:16:00 to 29-FEB-12 04:18:00 (CST-6)
Location: MAKANDA
Magnitude: 96.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A downburst averaging 1/2 mile wide resulted in thousands of trees being snapped or uprooted in the Devil's Kitchen Lake area, around and east of the Giant City State Park area. Peak winds were estimated near 110 mph.

Tornado in UNION, ILLINOIS
From 29-FEB-12 04:00:00 to 29-FEB-12 04:18:00 (CST-6)
Location: ALDRIDGE
Tornado F-scale: EF2
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado crossed the Mississippi River from Cape Girardeau County into northwestern Union County. After exiting cropland in the Mississippi River floodplain, the tornado tracked through the Shawnee National Forest. The damage path extended just north of Bald Knob, then directly across Alto Pass. Thousands of trees were snapped or uprooted, and several houses were damaged. The houses that were damaged suffered primarily partial roof loss. The houses were located in Alto Pass, where EF-2 damage occurred. Numerous barns and grain bins were destroyed. Many power lines were blown down. Peak winds were estimated near 115 mph. The average path width was 250 yards. The tornado path crossed into Giant City State Park and into the southeast corner of Jackson County.

Tornado in WILLIAMSON, ILLINOIS
From 29-FEB-12 04:26:00 to 29-FEB-12 04:40:00 (CST-6)
Location: WOLF CREEK
Tornado F-scale: EF2
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado was spawned by the same supercell that produced an EF-2 tornado in Union and extreme southeast Jackson Counties. The tornado touched down in the Crab Orchard National Wildlife Refuge, just southeast of Little Grassy Lake. The tornado moved east-northeast across Interstate 57, passing south of Marion. A large metal warehouse building was heavily damaged. Numerous homes sustained mainly minor roof damage. Hundreds of trees were snapped or uprooted, and many power lines were blown down. Several barns and outbuildings were destroyed or heavily damaged. The peak EF-2 intensity estimate was based on damage southeast of Marion, near the location where the tornado crossed Highway 166. Peak winds were estimated near 120 mph. The average path width was 250 yards.

Tornado in PULASKI, ILLINOIS
From 29-FEB-12 05:00:00 to 29-FEB-12 05:07:00 (CST-6)
Location: MOUNDS
Tornado F-scale: EF2
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The EF2 tornado touched down just southwest of Mounds, moved east-northeast through Mounds, and crossed Interstate 57 near exit 8. A cross arm was ripped off a railroad sign and driven into a vehicle. The tornado crossed the Ohio River near the town of America, where it proceeded to cause damage in Ballard County, Kentucky.

Tornado in GALLATIN, ILLINOIS
From 29-FEB-12 05:04:00 to 29-FEB-12 05:13:00 (CST-6)
Location: EQUALITY
Tornado F-scale: EF4
Property damage: 1.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado crossed into Gallatin County from Saline County in the vicinity of Illinois Highway 142. The tornado moved east-northeast through very sparsely populated farm country before striking Ridgway directly. In Ridgway, the tornado damaged about 140 homes and businesses, causing one critical injury and about a dozen relatively minor injuries. Numerous cars were tossed around, mainly on the east side of Ridgway. A large historic church was completely destroyed. Hundreds of large trees were snapped or uprooted, along with many power lines down. A half dozen grain bins were destroyed. The tornado lifted about 4 miles east-northeast of Ridgway. The average path width was 275 yards. Peak winds were estimated near 180 mph.

Thunderstorm Wind in MASSAC, ILLINOIS
From 29-FEB-12 05:23:00 to 29-FEB-12 05:28:00 (CST-6)
Location: ROUND KNOB
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A wind gust was measured to 60 mph.