A warm front across the region was the focus of thunderstorm development.  A mesoscale convective system developed during the evening of June 25th and moved east across the region.  There were numerous reports of large hail, damaging winds and flash flooding.

Hail in JERSEY, ILLINOIS
From 25-JUN-11 18:40:00 to 25-JUN-11 18:45:00 (CST-6)
Location: GRAFTON
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Most of the hail was an inch or less in size.

Hail in MADISON, ILLINOIS
From 25-JUN-11 22:05:00 to 25-JUN-11 22:06:00 (CST-6)
Location: ALTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CLINTON, ILLINOIS
From 25-JUN-11 22:45:00 to 25-JUN-11 22:45:00 (CST-6)
Location: KEYESPORT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew down several large trees and tree limbs.  A few of the limbs landed on power lines, knocking them down.

Thunderstorm Wind in CLINTON, ILLINOIS
From 25-JUN-11 22:56:00 to 25-JUN-11 22:56:00 (CST-6)
Location: AVISTON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew down several large tree limbs and a couple of power lines.

Flash Flood in ADAMS, ILLINOIS
From 25-JUN-11 20:00:00 to 26-JUN-11 01:00:00 (CST-6)
Location: MEYER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Up to three inches of rain fell onto already saturated soils in a short amount of time causing flash flooding.  Numerous roads were flooded, especially in the northern half of Adams county near Camp Point, Golden and Loraine.  Water was over a foot deep in some locations.

Flash Flood in BOND, ILLINOIS
From 26-JUN-11 00:00:00 to 26-JUN-11 05:00:00 (CST-6)
Location: MULBERRY GROVE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Up to three inches of rain fell in a short amount of time onto already saturated soils causing flash flooding.  Several roads were flooded including Illinois Route 140 near Greenville.

Flash Flood in RANDOLPH, ILLINOIS
From 26-JUN-11 01:00:00 to 26-JUN-11 05:00:00 (CST-6)
Location: COULTERVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Up to three inches of rain fell in a short amount of time onto already saturated soils causing flash flooding.  Several roads were flooded including Illinois Route 153 southwest of Coulterville.

Thunderstorm Wind in WASHINGTON, ILLINOIS
From 26-JUN-11 02:30:00 to 26-JUN-11 02:30:00 (CST-6)
Location: CORDES
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Thunderstorm winds destroyed a machine shed.  The debris was thrown against the garage causing moderate damage to the garage.

Flash Flood in BROWN, ILLINOIS
From 25-JUN-11 21:00:00 to 26-JUN-11 01:30:00 (CST-6)
Location: DAMON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Up to three inches of rain fell onto already saturated soils in a short amount of time causing flash flooding.  Numerous roads were flooded including County Road 825 west of Cooperstown.

Flash Flood in ST. CLAIR, ILLINOIS
From 26-JUN-11 00:00:00 to 26-JUN-11 05:00:00 (CST-6)
Location: MONSANTO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Up to four inches of rain fell in a short amount of time onto already saturated soils causing flash flooding.  Numerous roads were flooded including the intersection of Illinois Routes 13 and 157.  Water rescue had to be performed at this location.  Not long afterwards the two cars were almost completely submerged in the standing water at this intersection.