During the afternoon hours of August 3rd, numerous thunderstorms developed across parts of eastern Missouri and west-central Illinois, triggered by strong surface heating ahead of a surging outflow boundary. These storms developed within a strongly unstable environment, featuring MLCAPE values ranging from 2500 to as much as 4000 J/kg and largely driven by the very warm and humid boundary layer. The initial round of storms struggled to become organized. Eventually cold pool interactions drove upscale growth into a more linear complex. Damaging winds, occasional large hail were reported as well as bursts of very heavy rain rates. By the evening of August 3rd, storms grew upscale, with additional rounds of thunderstorms developing upstream from this initial activity. The primary hazard transitioned from a damaging wind threat to a heavy rain and flash flooding threat, as storms were extremely efficient rain producers. Warm cloud depths were around 4.5km, along with anomalously high precipitable water values of 2 to 2.5 inches, and Corfidi vector orientations that supported westward back-building which enhanced the potential for locally heavy rain, both in terms of instantaneous rates (2+ inches per hour at times) and training of storms. By mid morning on August 4th, widespread rainfall amounts of 1 to 3 inches fell, mainly along and south of I-70 in Missouri and along and east of I-55 in Illinois. Over the St. Louis metro area, as well as Fredericktown, MO, between 4 and 7 inches of rain fell. There were numerous reports of flash flooding in these areas.

Hail in ST. LOUIS, MISSOURI
From 03-AUG-22 14:43:00 to 03-AUG-22 14:43:00 (CST-6)
Location: BLACK JACK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in WARREN, MISSOURI
From 03-AUG-22 14:13:00 to 03-AUG-22 14:18:00 (CST-6)
Location: PEERS
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds blew down several large trees onto Highway 94 just west of Marthasville.

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 03-AUG-22 14:30:00 to 03-AUG-22 14:30:00 (CST-6)
Location: BRECKENRIDGE HILLS
Magnitude: 61.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds uprooted a large tree.

Thunderstorm Wind in JEFFERSON, MISSOURI
From 03-AUG-22 16:20:00 to 03-AUG-22 16:35:00 (CST-6)
Location: DE SOTO
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm winds blew down numerous large tree limbs in DeSoto. Also, a large tree was blown over onto Highway V just northwest of Valles Mines.

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 03-AUG-22 14:36:00 to 03-AUG-22 14:42:00 (CST-6)
Location: FLORISSANT
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm winds blew down numerous large tree limbs, as well as several power lines. Also, minor shingle damage to a couple of homes.

Flash Flood in MADISON, MISSOURI
From 04-AUG-22 02:30:00 to 04-AUG-22 06:23:00 (CST-6)
Location: ROSELLE
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Between 6 and 7 inches of rain fell in about a 2 to 3 hour period across northern portions of Madison County. Numerous creeks flooded, including Saline Creek in Fredericktown. Also, several rivers flooded including Little St. Francois River in Fredericktown, which rose 18.6 feet in 5 hours, cresting at 20.49 feet by 715 am. At least 21 people were rescued from the flood waters in and around Fredericktown. One person drove into flood waters on Highway Z on the east side of town and floated into the ditch. They were rescued and sustained no injuries. The flash flooding affected the Holmes Subdivision as well as other homes and businesses along Saline Creek and a creek along South Mine La Motte Avenue.

Flash Flood in ST. LOUIS, MISSOURI
From 03-AUG-22 21:35:00 to 04-AUG-22 01:00:00 (CST-6)
Location: CHESTERFIELD
Flood cause: Heavy Rain
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread flash flooding occurred across St. Louis County, especially in the Hazelwood, Maryland Heights, Creve Coeur, Frontenac, Oakville, and Fenton. Up to five inches of rain fell in a 4 to 5 hour period. Numerous roads were flooded including Lindbergh Blvd., Schuetz Road and Fee Fee Road. Several water rescues were performed. One rescue occurred at the intersection of Fee Fee Road and Grissom Drive, another on Lindbergh near Candle Light Lane, and one on Lindbergh near Clayton Terrace.

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 03-AUG-22 21:30:00 to 03-AUG-22 21:35:00 (CST-6)
Location: LADUE
Magnitude: 56.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm winds blew down numerous large tree limbs in Ladue. In Warson Woods, a large tree was blown down onto a local road blocking it. In Kirkwood, a large tree was blown down on Sugar Creek Ridge Drive knocking down powerlines and poles.

Flash Flood in ST. LOUIS, MISSOURI
From 04-AUG-22 06:10:00 to 04-AUG-22 09:10:00 (CST-6)
Location: PATTONVILLE
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Public

Second round of heavy rain fell across portions of St. Louis County during the morning hours of August 4th. Up to 4 inches fell in a short amount of time, especially in the Warson Woods, Frontenac, Kirkwood, Glendale, Sunset Hills, Crestwood, and Webster Groves areas.  Numerous roads were flooded including U.S. Highway 67 just south of Frontenac, Highway 100 (Manchester Road) east of McKnight Road due to flooding of Deer Creek, North Berry Road near Clif-Side Drive due to Shady Grove Creek flooding, and Big Bend Road near Sanders Drive due to Gravois Creek flooding. Several businesses sustained flood damage, especially along Manchester Road. Some vehicles were stranded in flood waters. No injuries were reported.

Flash Flood in JEFFERSON, MISSOURI
From 03-AUG-22 23:40:00 to 04-AUG-22 02:00:00 (CST-6)
Location: HIGH RIDGE
Flood cause: Heavy Rain
Property damage: 120.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Up to five inches of rain fell in a short amount of time causing flash flooding in the far northern portions of the county. Numerous roads were flooded including Highway 141. There were multiple water rescues on Highway 141, but no injuries were reported. Also, several water evacuations were performed at homes near the intersection of Romaine Creek Road and Konert Road. Twenty four home sustained minor flood damage.