A strong cold front moved through region. With plenty of moisture, instability and decent low level shear, severe storms developed along the Interstate 70 corridor in Missouri and Illinois.  Numerous reports of large hail and 5 tornadoes occurred with this event.  One of the tornadoes was a long track one that moved through the St. Louis metropolitan area with it being rated an EF4, with only a few minor injuries and no deaths. Also, quite a bit of rain fell during this event and caused flash flooding.  The flash flooding persisted for several days as additional rounds of heavy rain fell over the same region through the 26th of April.

Tornado in ST. LOUIS, MISSOURI
From 22-APR-11 18:59:00 to 22-APR-11 19:22:00 (CST-6)
Location: VIGUS
Tornado F-scale: EF4
Property damage: 250.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

During the evening of Friday April 22nd, an intense supercell thunderstorm produced a long-track tornado which tore a path of destruction from west to east across the St. Louis Metropolitan Area, from St. Louis County Missouri eastward through the far northern portions of the City of St. Louis, then across the Mississippi River into Madison County Illinois. The tornado reached a maximum intensity of EF4 on the Enhanced Fujita Scale as it tracked through the community of Bridgeton, just west of Lambert St. Louis International Airport, in St. Louis County. The total path length was 21.3 miles, with a width of up to half a mile.
The tornado initially touched down along the northern edge of Creve Coeur Lake at approximately 759 pm.  It tracked nearly due east at about 40 mph, and intensified as it entered Maryland Heights. There it produced up to EF3 damage to many homes and businesses with a damage swath of 200 to 400 yards wide.  Damage continued eastward in an unbroken track, crossing I-270 about 1 mile south of I-70. The tornado reached peak intensity of EF4 as it devastated the community of Bridgeton along Old St. Charles Road.  From there the tornado paralleled Interstate 70 through the community of St. Ann, and then took aim directly on Lambert-St. Louis International Airport.  Many of the large windows in the main terminal building were blown out or damaged by flying debris and a large section of roof was peeled from Concourse C.  Although the vast majority of people were evacuated to lower levels and to interior rooms before the tornado hit, five people were treated and released from area hospitals for injuries due to flying debris. The airport was closed due to the extensive damage.  Damage at the airport was estimated to be between $35 to 40 million.

The tornado exited Lambert-St. Louis International Airport crossing near the McDonnell Boulevard/Harmon Lane intersection.  It then moved into Berkeley where it crossed Interstate 170 between Airport Road and Scudder Avenue. Extensive damage was noted along Fourth Avenue, especially at the Garfield Avenue and Hancock Avenue intersections where a vacant house and several homes lost their entire roof structure. The greatest damage in this neighborhood was rated EF2.  The tornado continued to the northeast through neighborhoods south of Airport Road producing significant tree damage including many large trees falling on homes.  The tornado then crossed Airport Road near Abston Street.  The tornado crossed North Florissant Road where it caused extensive roof damage to the Newger Materials building and the First Baptist Church of Ferguson.  Across the road, a Little Caesars Restaurant lost its entire roof. Damage to these structures was rated EF1. The tornado then continued through neighborhoods along and just the north of Hereford Avenue/Chambers Road where it continued to cause extensive tree damage as well as additional partial roof damage to homes along the path toward West Florissant Road.  Also along this part of its path, it partially removed the roof at the Griffith Elementary School which was rated as EF1. This is also where the tornado widened to one quarter of a mile with damage noted to trees and some homes on both sides of Chambers Road.  Along the entire path from Berkeley to Dellwood, damage varied in intensity from EF1 to low end EF2 with a maximum estimated wind speed of 120 mph, and included numerous snapped power poles in addition to the extensive number of snapped and downed trees.
EF2 damage was uncovered at three different locations east of Dellwood. One area was located one quarter mile south of Chambers Road on Halls Ferry Road where four large utility poles were snapped. The second area of EF2 damage was located a quarter of a mile south of Chambers Road along Bellefontaine Road where significant tree damage occurred. The last area of damage was located in Bellefontaine Neighbors just south of Chambers Road on La Roux Court. Roofs were removed from three homes at this location, while other homes sustained varying degrees of damage.  The width of the damage area varies from 100 yards to four tenths of a mile with the widest area of damage east of Halls Ferry and south of Chambers Road.
The tornadic damage continued as the tornado traveled eastward south of Chambers road, crossing into the far northern portions of the city of St. Louis. The majority of the damage in this area was rated EF1 due to fallen trees. Some of these trees fell on homes while a few others fell through homes causing damage not directly relating to the intensity of the wind within the tornado.
Overall, in St. Louis County, 233 structures (homes and businesses) sustained major damage, 776 structures sustained moderate damage, and 1,487 structures sustained minor damage.  Estimated dollar amount damage is $250 million.

Hail in CALLAWAY, MISSOURI
From 22-APR-11 17:14:00 to 22-APR-11 17:14:00 (CST-6)
Location: PORTLAND
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in MONTGOMERY, MISSOURI
From 22-APR-11 17:25:00 to 22-APR-11 17:30:00 (CST-6)
Location: BIG SPG
Magnitude: 4.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous reports of large hail ranging from baseball to grapefruit size in an area between Big Spring and Hermann Country Club, just north of McKittrick.

Hail in MONTGOMERY, MISSOURI
From 22-APR-11 17:18:00 to 22-APR-11 17:20:00 (CST-6)
Location: AMERICUS
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A swath of large hail fell over southern Montgomery County, from the Callaway/Montgomery County line eastward towards Americus.

Hail in ST. LOUIS, MISSOURI
From 22-APR-11 19:30:00 to 22-APR-11 19:30:00 (CST-6)
Location: OAKVILLE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ST. CHARLES, MISSOURI
From 22-APR-11 18:47:00 to 22-APR-11 18:53:00 (CST-6)
Location: ST PETERS
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotters estimated 70 to 80 mph winds when the storms moved along Interstate 70 near St. Peters.

Flash Flood in FRANKLIN, MISSOURI
From 22-APR-11 19:45:00 to 23-APR-11 00:30:00 (CST-6)
Location: GRAY SUMMIT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to three inches of rain fell in a short amount of time causing flash flooding.  Several roads had water over them including Highway MM just northwest of Gray Summit.

Hail in OSAGE, MISSOURI
From 22-APR-11 17:30:00 to 22-APR-11 17:35:00 (CST-6)
Location: LINN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in CALLAWAY, MISSOURI
From 23-APR-11 08:44:00 to 23-APR-11 08:44:00 (CST-6)
Location: NEW BLOOMFIELD
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in OSAGE, MISSOURI
From 22-APR-11 17:30:00 to 22-APR-11 17:33:00 (CST-6)
Location: LINN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MONTGOMERY, MISSOURI
From 22-APR-11 17:44:00 to 22-APR-11 17:49:00 (CST-6)
Location: JONESBURG
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in WARREN, MISSOURI
From 22-APR-11 17:44:00 to 22-APR-11 17:44:00 (CST-6)
Location: WARRENTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in WARREN, MISSOURI
From 22-APR-11 17:44:00 to 22-APR-11 17:55:00 (CST-6)
Location: PENDLETON
Magnitude: 4.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A swath of large hail fell over the Warrenton area.  The biggest hail stones were softball size.

Tornado in ST. CHARLES, MISSOURI
From 22-APR-11 18:17:00 to 22-APR-11 18:32:00 (CST-6)
Location: NEW MELLE
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado first touched down along Freese Lane around a tenth of a mile south of Foristell Road approximately three and a half miles to the northwest of New Melle. The tornado travelled to the east moving into the Auburn Meadows Subdivision where it caused damage to nine homes. The most significant damage occurred when one home lost almost half its roof after the attached garage was destroyed. Damage to this home was rated EF1. The rest of the homes suffered lesser degrees of roof damage.  A van was also pushed approximately 30 yards from a driveway into an open grassy area. The tornado then continued to the east along Foristell Road causing damage to trees and several homes. At the Jimmie Hite Horse Stables, several large outbuildings were also heavily damaged. To the east of the stables, a horse arena was demolished. The tornado then continued to move east where it snapped or blew down many trees either side of Highway Z. The tornado continued to the east and moved into the Avondale Hills Subdivision causing minor roof damage to a few homes before lifting and dissipating just east of State Highway DD, north of the intersection with Schwede Road.  The maximum intensity was EF1 with a maximum wind speed of 110 mph.  The total path length was 7.4 miles with a maximum width 250 yards.

Flash Flood in ST. LOUIS, MISSOURI
From 22-APR-11 20:10:00 to 23-APR-11 00:30:00 (CST-6)
Location: FENTON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to three inches of rain fell in a short amount of time causing flash flooding.  Several roads had water over them.  Also, a creek rose above its banks with the water surrounding some houses in the area from two to six inches deep.

Hail in WARREN, MISSOURI
From 22-APR-11 17:55:00 to 22-APR-11 18:05:00 (CST-6)
Location: WRIGHT CITY
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ST. LOUIS, MISSOURI
From 22-APR-11 19:30:00 to 22-APR-11 19:30:00 (CST-6)
Location: SAPPINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in ST. LOUIS (C), MISSOURI
From 22-APR-11 19:22:00 to 22-APR-11 19:24:00 (CST-6)
Location: BADEN
Tornado F-scale: EF1
Crop damage: 0.00K
Reported by: NWS Storm Survey

During the evening of Friday April 22nd, an intense supercell thunderstorm produced a long-track tornado which tore a path of destruction from west to east across the St. Louis Metropolitan Area, from St. Louis County Missouri eastward through the far northern portions of the City of St. Louis, then across the Mississippi River into Madison County Illinois. The tornado reached a maximum intensity of EF4 on the Enhanced Fujita Scale as it tracked through the community of Bridgeton, just west of Lambert St. Louis International Airport, in St. Louis County. The total path length was 21.3 miles, with a width of up to half a mile.
As the tornado crossed from St. Louis County into the far northern portions of the City of St. Louis, there was EF-1 tree damage and minor roof and siding damage which was rated EF-0.  The tornado continued to travel to the east and crossed the Mississippi River into Madison County Illinois, approximately 1.5 miles south of Interstate 270.

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:15:00 to 22-APR-11 18:20:00 (CST-6)
Location: WENTZVILLE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:10:00 to 22-APR-11 18:10:00 (CST-6)
Location: FLINT HILL
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in MONITEAU, MISSOURI
From 22-APR-11 16:00:00 to 22-APR-11 16:04:00 (CST-6)
Location: KLIEVER
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COLE, MISSOURI
From 22-APR-11 16:10:00 to 22-APR-11 16:10:00 (CST-6)
Location: MARION
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in BOONE, MISSOURI
From 22-APR-11 16:23:00 to 22-APR-11 16:30:00 (CST-6)
Location: ASHLAND
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Lots of hail up to golfball size was reported in the Ashland area.

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:28:00 to 22-APR-11 18:33:00 (CST-6)
Location: O FALLON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:27:00 to 22-APR-11 18:33:00 (CST-6)
Location: GILMORE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:38:00 to 22-APR-11 18:41:00 (CST-6)
Location: DARDENNE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in ST. CHARLES, MISSOURI
From 22-APR-11 18:42:00 to 22-APR-11 18:46:00 (CST-6)
Location: ALL SAINTS VLG
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wide swath of large hail was reported with the biggest stone being 2 inches in diameter.

Hail in BOONE, MISSOURI
From 22-APR-11 16:30:00 to 22-APR-11 16:30:00 (CST-6)
Location: HARTSBURG
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CALLAWAY, MISSOURI
From 22-APR-11 16:42:00 to 22-APR-11 16:50:00 (CST-6)
Location: FULTON ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CALLAWAY, MISSOURI
From 22-APR-11 16:34:00 to 22-APR-11 16:34:00 (CST-6)
Location: GUTHRIE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CALLAWAY, MISSOURI
From 22-APR-11 16:47:00 to 22-APR-11 16:47:00 (CST-6)
Location: DIXIE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in FRANKLIN, MISSOURI
From 22-APR-11 18:46:00 to 22-APR-11 18:46:00 (CST-6)
Location: ST CLAIR
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in FRANKLIN, MISSOURI
From 22-APR-11 18:44:00 to 22-APR-11 18:44:00 (CST-6)
Location: UNION
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in FRANKLIN, MISSOURI
From 22-APR-11 18:50:00 to 22-APR-11 18:50:00 (CST-6)
Location: VILLA RIDGE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ST. CHARLES, MISSOURI
From 22-APR-11 18:45:00 to 22-APR-11 18:45:00 (CST-6)
Location: O FALLON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds blew down a large tree onto an unoccupied car.

Flash Flood in ST. FRANCOIS, MISSOURI
From 22-APR-11 23:00:00 to 26-APR-11 03:50:00 (CST-6)
Location: SILVER SPGS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Between 6 and 9 inches fell over several days on already saturated grounds causing flash flooding.  Numerous roads were flooded including U.S. Highway 67 in Farmington.  Also, there was three feet of flowing water near the intersection of Veterans Drive and East College Street.  Intersection of Highways OO and DD, just southwest of Libertyville was closed due to flooding.  The Big River flooded well out of its banks making Turkey Creek Road impassable north of Bonne Terre.  Several water rescues had to be performed.