A vigorous upper-level disturbance interacting with an approaching cold front triggered severe thunderstorms across central and southeast Illinois during the afternoon and evening of April 15th.  The airmass ahead of the front was moderately unstable and highly sheared.  As a result, several supercell thunderstorms developed along and west of the I-55 corridor.  The storms produced numerous funnel clouds and three confirmed tornadoes.  Hail up to 2 inches in diameter was observed as well.  The storms eventually congealed into a linear structure and weakened as they pushed into east-central and southeast Illinois during the mid to late evening.

Hail in CASS, ILLINOIS
From 15-APR-11 17:30:00 to 15-APR-11 17:31:00 (CST-6)
Location: NEWMANSVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in TAZEWELL, ILLINOIS
From 15-APR-11 18:42:00 to 15-APR-11 18:43:00 (CST-6)
Location: DELAVAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in LAWRENCE, ILLINOIS
From 15-APR-11 19:13:00 to 15-APR-11 19:14:00 (CST-6)
Location: BIRDS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in SCHUYLER, ILLINOIS
From 15-APR-11 15:37:00 to 15-APR-11 15:38:00 (CST-6)
Location: HUNTSVILLE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MORGAN, ILLINOIS
From 15-APR-11 16:40:00 to 15-APR-11 16:41:00 (CST-6)
Location: WAVERLY
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in SANGAMON, ILLINOIS
From 15-APR-11 16:45:00 to 15-APR-11 16:46:00 (CST-6)
Location: TORONTO
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in SANGAMON, ILLINOIS
From 15-APR-11 16:55:00 to 15-APR-11 16:56:00 (CST-6)
Location: SPRINGFIELD
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SANGAMON, ILLINOIS
From 15-APR-11 16:59:00 to 15-APR-11 17:00:00 (CST-6)
Location: PAWNEE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in FULTON, ILLINOIS
From 15-APR-11 17:05:00 to 15-APR-11 17:06:00 (CST-6)
Location: ST DAVID
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in SANGAMON, ILLINOIS
From 15-APR-11 17:06:00 to 15-APR-11 17:07:00 (CST-6)
Location: CHATHAM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in SANGAMON, ILLINOIS
From 15-APR-11 17:12:00 to 15-APR-11 17:13:00 (CST-6)
Location: SOUTHLAWN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Golfball-sized hail was reported on the east side of Lake Springfield.

Hail in SANGAMON, ILLINOIS
From 15-APR-11 17:22:00 to 15-APR-11 17:23:00 (CST-6)
Location: (SPI)SPRINGFIELD ARP
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Golfball-sized hail was reported at the Springfield Airport.

Tornado in MENARD, ILLINOIS
From 15-APR-11 17:22:00 to 15-APR-11 17:25:00 (CST-6)
Location: ATHENS
Tornado F-scale: EF0
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down in a field 1 mile northeast of Athens at 622 PM CDT.  It moved north-northwest...damaging a window, siding, and gutters on a house before dissipating 2 miles north-northeast of Athens at 624 PM CDT.

Tornado in MENARD, ILLINOIS
From 15-APR-11 17:25:00 to 15-APR-11 17:31:00 (CST-6)
Location: CULVER
Tornado F-scale: EF1
Property damage: 450.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down in a field 3 miles northeast of Athens at 625 PM CDT.  It tracked northward...damaging the roof of a house, destroying a small garage, and damaging several automobiles.  Further north, the tornado knocked two trees down onto a house, doing severe damage to its roof and interior walls.  It then tipped over a semi-trailer and damaged several trees before dissipating 4.8 miles north-northeast of Athens at 631 PM CDT.

Thunderstorm Wind in MENARD, ILLINOIS
From 15-APR-11 17:33:00 to 15-APR-11 17:38:00 (CST-6)
Location: SWEET WATER
Magnitude: 70.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Downburst winds did minor damage to a lean-to-shed and the roof of a house and knocked down several trees at the Sugar Grove Cemetary.

Thunderstorm Wind in LOGAN, ILLINOIS
From 15-APR-11 17:46:00 to 15-APR-11 17:51:00 (CST-6)
Location: MIDDLETOWN
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A tree was blown down onto the Greenview Blacktop just southwest of Middletown.

Thunderstorm Wind in CLAY, ILLINOIS
From 15-APR-11 17:50:00 to 15-APR-11 17:55:00 (CST-6)
Location: FLORA
Magnitude: 52.00 EG
Property damage: 12.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A tree was blown down onto a house in Flora.

Flash Flood in MASON, ILLINOIS
From 15-APR-11 18:30:00 to 15-APR-11 23:30:00 (CST-6)
Location: CHAUTAUQUA PARK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several rounds of heavy rainfall, ranging from 3.00 to 4.00 inches in four hours, resulted in flash flooding of rural roads and creeks in central and southern Mason County.

Tornado in MASON, ILLINOIS
From 15-APR-11 16:30:00 to 15-APR-11 16:38:00 (CST-6)
Location: POPLAR CITY
Tornado F-scale: EF1
Property damage: 300.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down in a field about 6.5 miles west-southwest of Easton at 530 PM CDT.  It knocked over an irrigation unit and damaged an outbuilding before traveling north and damaging several sheds, breaking windows, tearing roofing and siding off a house, and pushing a house a few inches off its foundation.  One person was injured by flying glass.  The tornado then damaged another outbuilding and several trees before dissipating 7 miles west-northwest of Easton at 538 PM CDT.

Hail in SANGAMON, ILLINOIS
From 15-APR-11 18:00:00 to 15-APR-11 18:01:00 (CST-6)
Location: BUFFALO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer