A backbuilding cluster of thunderstorms near the MO/IA border slowly sagged southward during the afternoon hours on August 12th.  An additional cluster of thunderstorms congealed across northeastern Kansas into north-central Missouri and merged into the backbuilding cluster. These thunderstorms developed ahead of a synoptic cold front. As these storms moved southeast across the region, some became severe and produced widespread damaging winds.

Thunderstorm Wind in LINCOLN, MISSOURI
From 12-AUG-21 16:45:00 to 12-AUG-21 17:01:00 (CST-6)
Location: TROY
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A line of severe storms moved east across Lincoln County. Numerous trees, tree limbs and power lines were blown down. In Troy, a large tree limb was blown onto a house causing minor roof damage. East of Troy along Highway 47, three power poles were snapped off.

Thunderstorm Wind in ST. CHARLES, MISSOURI
From 12-AUG-21 17:02:00 to 12-AUG-21 17:21:00 (CST-6)
Location: FORISTELL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread damaging winds across the western portions of St. Charles County. Numerous trees, tree limbs and power lines were blown down. One large tree was blown down onto W. Meyer Road in Wentzville. Also, several trees were blown down near the intersection of Mexico Road and Belleau Creek Road, and the intersection of Highways K and N.  A tree and power line were blown down over Highway DD near intersection with Highway 94.

Thunderstorm Wind in FRANKLIN, MISSOURI
From 12-AUG-21 17:21:00 to 12-AUG-21 17:24:00 (CST-6)
Location: LABADIE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm gust front winds blew down several trees and power lines in Labadie. Numerous tree limbs were blown down near Gray Summit.

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 12-AUG-21 17:25:00 to 12-AUG-21 18:00:00 (CST-6)
Location: VIGUS
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread thunderstorm wind damage across a large portion of St. Louis County.  Numerous trees, tree limbs and power lines were blown down.  In Eureka, several houses had minor shingle damage. In Florissant, a large tree limb was blown down onto a house causing moderate damage. In Kirkwood, a number of trees were blown down near the intersection of Manchester Road and Geyer Road.  A large tree was snapped in half on Pine Avenue in Brentwood, landing on a nearby house, causing moderate damage. A tree was blown down onto Watson Road in Webster Groves.

Thunderstorm Wind in JEFFERSON, MISSOURI
From 12-AUG-21 17:41:00 to 12-AUG-21 18:05:00 (CST-6)
Location: MURPHY
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A swath of damaging winds from Murphy southeastward into Herculaneum.  Numerous trees, tree limbs and power lines were blown down.

Thunderstorm Wind in ST. LOUIS (C), MISSOURI
From 12-AUG-21 17:44:00 to 12-AUG-21 17:55:00 (CST-6)
Location: TOWER GROVE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Damaging thunderstorm winds moved across the western and southern portions of the City of St. Louis. Several trees and numerous tree limbs were blown down. Several trees were blown down across McCausland Avenue.

Thunderstorm Wind in WARREN, MISSOURI
From 12-AUG-21 16:58:00 to 12-AUG-21 16:58:00 (CST-6)
Location: WARRENTON
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Thunderstorm winds peeled off a portion of a flat roof on Daniel Boone Elementary School in the Warren County R-III School District.

Thunderstorm Wind in AUDRAIN, MISSOURI
From 12-AUG-21 15:45:00 to 12-AUG-21 15:55:00 (CST-6)
Location: MEXICO
Magnitude: 53.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm winds blew down numerous tree limbs around Mexico and areas to the south and southeast of town.

Thunderstorm Wind in MARION, MISSOURI
From 12-AUG-21 15:45:00 to 12-AUG-21 15:55:00 (CST-6)
Location: HANNIBAL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread damaging winds occurred across Hannibal. Numerous large trees, tree limbs and power lines were blown down. One tree was blown down onto an unoccupied camper and another tree was blown down onto an unoccupied car. A hardware store in town sustained moderate roof damage. Also, a large portion of a flat metal roof was removed from a building on the Hannibal-LaGrange University Campus. Several trees and numerous tree limbs were blown down on campus as well.