Scattered thunderstorms moved across portions of central Illinois during the afternoon and evening of July 12th.  One storm moved very slowly over eastern La Salle and western Grundy Counties.  Torrential rain produced flash flooding in these areas with numerous roads flooded and at least four bridges damaged.

Thunderstorm Wind in IROQUOIS, ILLINOIS
From 12-JUL-21 13:47:00 to 12-JUL-21 13:47:00 (CST-6)
Location: ASHKUM
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several tree limbs were blown down along Route 45.

Flood in LA SALLE, ILLINOIS
From 13-JUL-21 00:30:00 to 13-JUL-21 09:30:00 (CST-6)
Location: SENECA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Flooding continued across portions of eastern LaSalle County during the morning of July 13th after flash flooding during the evening of July 12th.

Flood in GRUNDY, ILLINOIS
From 13-JUL-21 00:30:00 to 13-JUL-21 09:30:00 (CST-6)
Location: KINSMAN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Flooding continued across portions of western Grundy County during the morning of July 13th after flash flooding during the evening of July 12th.

Flood in GRUNDY, ILLINOIS
From 12-JUL-21 23:15:00 to 13-JUL-21 03:00:00 (CST-6)
Location: BRACEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Six to eight inches of standing water was reported in yards on the north side of Braceville.

Flash Flood in GRUNDY, ILLINOIS
From 12-JUL-21 20:10:00 to 13-JUL-21 00:30:00 (CST-6)
Location: KINSMAN
Flood cause: Heavy Rain
Property damage: 300.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A slow moving thunderstorm produced torrential rain and flash flooding across portions of western Grundy County.  Vegetation was flattened near many creeks and channels due to the fast moving flood waters.  Along Armstrong Run, water went over the Indian Trail Road bridge.  Damage occurred to the bridge approaches and pavement was missing.  A nearby shed was destroyed and a utility pole was toppled.  Further northeast, the Kinsman Road bridge over Armstrong Run was also damaged.  Significant damage occurred to vegetation including entire trees removed.  Damage also occurred to the Dupont Road bridge over Armstrong Run where the approaches suffered significant scouring.  Vegetation was flattened and a nearby fence was knocked over with evidence of 1 to 2 feet of flowing water.  The Dupont Road bridge over Hog Run was damaged with the approaches washed out.  Vegetation was flattened in many locations near Hog Run between Omalley and Grand Ridge Roads.  Water rescues were performed during the peak of the flooding near Kinsman and Dupont Roads where at least three vehicles were stuck in flood waters.  Rainfall of 6.19 inches was reported during a 3 hour period, four miles northwest of Verona.  Rainfall of 4.58 inches was reported during a 4 hour period, three miles east of Seneca.  The damage amount was estimated in consultation with local emergency management officials.

Flash Flood in LA SALLE, ILLINOIS
From 12-JUL-21 20:00:00 to 13-JUL-21 00:30:00 (CST-6)
Location: SENECA
Flood cause: Heavy Rain
Property damage: 1.20M
Crop damage: 0.00K
Reported by: NWS Storm Survey

A slow moving thunderstorm produced torrential rain and flash flooding across portions of eastern La Salle County including in Seneca.  Vegetation was flattened near many creeks and channels due to the fast moving flood waters.  Along Hog Run, vegetation was flattened near North 21st Road with debris near the road.  Along North 2350th Road near Armstrong Run, flood waters flowed over the roadway with debris in the channel.  North La Salle Road was flooded, just south of Dupont Road with debris piled on the side of the road along with erosion in the channel.  There was substantial deposition of sediment from a nearby sand and gravel facility across Dupont Road near Deadly Run.  A substantial stretch of Dupont Road was flooded with extensive mud marking on pavement, east of Route 170 near a marina.  Just west of Route 170, the east abutment to the River Road bridge over a small creek was washed out.  A local highway department staff member was driving over this area when the washout occurred.  His truck became stuck on remaining pavement on either side of the washout.  The driver needed to be rescued and refused medical treatment.  Scouring occurred on both sides of the creek with vegetation collapsed or partially collapsed.  Homes on Timmons Lane were flooded with one home suffering a basement wall collapse.  Further west near River Road and Lake Street, flooding of several houses occurred as Spring Brook Creek overflowed with water flowing over fields and into the houses.  Significant damage occurred to vegetation where Spring Brook Creek crossed River Road.  Rainfall of 4.24 inches was reported during a 3 hour period, one mile east of Seneca.  The damage amount was estimated in consultation with local emergency management officials.