As a warm front lifted north through the forecast area, thunderstorms developed. Some of the storms became severe with numerous reports of large hail, some damaging winds and an EF2 tornado that occurred near Bourbon and Sullivan Missouri during the evening. The most costly damage occurred from a pair of supercells that dropped baseball to softball size hail across St. Charles County Missouri and produced severe wind gusts in St. Louis County and the City of St. Louis around the lunch hour.  There were also a few reports of flash flooding with these storms.

Flash Flood in MONROE, ILLINOIS
From 11-MAY-16 16:30:00 to 11-MAY-16 18:00:00 (CST-6)
Location: HARRISONVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to two inches of rain fell in a short amount of time causing flash flooding. Maeystown Creek was out of it's banks and flooding some roads in town.

Thunderstorm Wind in ST. CLAIR, ILLINOIS
From 11-MAY-16 13:35:00 to 11-MAY-16 13:35:00 (CST-6)
Location: SUMMERFIELD
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm winds blew down a large tree in Summerfield.

Hail in RANDOLPH, ILLINOIS
From 11-MAY-16 14:30:00 to 11-MAY-16 14:38:00 (CST-6)
Location: RED BUD
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in RANDOLPH, ILLINOIS
From 11-MAY-16 15:35:00 to 11-MAY-16 15:45:00 (CST-6)
Location: MODOC
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in RANDOLPH, ILLINOIS
From 11-MAY-16 16:00:00 to 11-MAY-16 16:00:00 (CST-6)
Location: EVANSVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in ADAMS, ILLINOIS
From 11-MAY-16 18:17:00 to 11-MAY-16 19:00:00 (CST-6)
Location: PAYSON
Magnitude: 4.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wide swath of large hail fell across the southern half of Adams County. The largest hailstone was 4.5 inches in Payson. Two inch hail was reported in Kellerville.

Hail in RANDOLPH, ILLINOIS
From 11-MAY-16 20:46:00 to 11-MAY-16 20:46:00 (CST-6)
Location: EVANSVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Thunderstorm Wind in MARION, ILLINOIS
From 11-MAY-16 14:15:00 to 11-MAY-16 14:50:00 (CST-6)
Location: SANDOVAL
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds blew down several large trees and numerous tree limbs between Sandoval and Salem.

Hail in MONROE, ILLINOIS
From 11-MAY-16 12:50:00 to 11-MAY-16 12:58:00 (CST-6)
Location: NEW HANOVER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MONROE, ILLINOIS
From 11-MAY-16 13:24:00 to 11-MAY-16 13:24:00 (CST-6)
Location: WATERLOO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MONROE, ILLINOIS
From 11-MAY-16 13:39:00 to 11-MAY-16 13:50:00 (CST-6)
Location: CHALFIN BRIDGE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in MADISON, ILLINOIS
From 11-MAY-16 13:00:00 to 11-MAY-16 13:07:00 (CST-6)
Location: SOUTH ROXANA
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Thunderstorm winds blew down several trees and large tree limbs between Wood River and South Roxana.  Also, in Wood River, some shingles were blown off of a house.

Hail in ST. CLAIR, ILLINOIS
From 11-MAY-16 13:10:00 to 11-MAY-16 13:10:00 (CST-6)
Location: NEW ATHENS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ST. CLAIR, ILLINOIS
From 11-MAY-16 13:14:00 to 11-MAY-16 13:30:00 (CST-6)
Location: MILLSTADT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CLINTON, ILLINOIS
From 11-MAY-16 14:00:00 to 11-MAY-16 14:00:00 (CST-6)
Location: BREESE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ST. CLAIR, ILLINOIS
From 11-MAY-16 13:35:00 to 11-MAY-16 13:35:00 (CST-6)
Location: ST LIBORY
Magnitude: 65.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorm winds blew down several large trees around town.  One tree fell onto Illinois Route 15, blocking it.

Thunderstorm Wind in CLINTON, ILLINOIS
From 11-MAY-16 13:35:00 to 11-MAY-16 14:00:00 (CST-6)
Location: NEW BADEN
Magnitude: 66.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm winds caused a wide swath of damage extending from New Baden area northeastward through Aviston, Breese and Carlyle. Numerous large trees, tree limbs and power lines were blown down.  In Breese, the top part of a grain silo was blown off.

Thunderstorm Wind in WASHINGTON, ILLINOIS
From 11-MAY-16 14:00:00 to 11-MAY-16 14:17:00 (CST-6)
Location: NEW MINDEN
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew down several large trees, numerous tree limbs and power lines between Okawville and New Minden.

Thunderstorm Wind in WASHINGTON, ILLINOIS
From 11-MAY-16 14:45:00 to 11-MAY-16 14:45:00 (CST-6)
Location: NASHVILLE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew down several large trees around town.