Storms developed along an outflow boundary that was laid out along the I-70 corridor.  The storms produced wind damage, large hail as well as 9 tornadoes.  Two of the tornadoes were rated EF3 as they moved through the St. Louis metro area.  Also, heavy rain fell causing flash flooding in some locations, which persisted into the early morning hours of June 1st.

Tornado in ST. CHARLES, MISSOURI
From 31-MAY-13 18:50:00 to 31-MAY-13 19:08:00 (CST-6)
Location: DEFIANCE
Tornado F-scale: EF3
Property damage: 50.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down about four miles southwest of Weldon Spring in St. Charles County, Missouri. It downed trees, blew over empty tractor trailers, and caused minor damage to construction equipment. It moved east-northeast into Weldon Spring Heights and the Missouri Research Park (on the south side of Weldon Spring) causing roof, window, and solar panel damage to a few structures as well as downing more trees before crossing Interstate 64. The tornado passed within one half of a mile of the National Weather Service Weather Forecast Office which is located in the Missouri Research Park. The tornado continued moving east-northeast through densely populated residential areas of southern St. Charles County, south of Highway 94. Roofing was torn off of Bryan Middle School and blown 100 yards, many houses suffered varying degrees of roof (from minor damage to removal of entire roof), wall (from minor damage to total collapse), and overall structural damage, and thousands of trees were damaged. The most intense damage, rated EF3, occurred on Haversham Drive where only the interior walls were left standing of three homes. The tornado began to move a bit more easterly, widening to nearly 1000 yards (or a half-mile), causing damage in residential areas and the St. Charles Family Arena before crossing the Missouri River into St. Louis County just south of Interstate 70.
The tornado caused damage to 765 homes in St. Charles County.  Seven hundred twenty-three homes suffered minor damage, 34 homes suffered major damage, and 8 homes were destroyed. Three hundred forty-eight businesses sustained minor damage, while 25 businesses had major damage. Cleanup costs alone for St. Charles County was 2.4 million dollars, with approximately 50,000 tons of tree and limb debris removed.  There were 8 minor injuries due to the tornado.
The path length of the tornado in St. Charles County was 14.8 miles with a max path width of 950 yards.  The damage for this segment was estimated to be EF3 with max wind speeds of 150 MPH.  Overall, the entire tornado path length was 31.8 miles with a max path width of 1 mile and a maximum damage rating of EF3.

Flash Flood in GASCONADE, MISSOURI
From 31-MAY-13 21:00:00 to 31-MAY-13 23:59:00 (CST-6)
Location: REDBIRD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to four inches of rain fell in a short amount of time causing flash flooding.  Several roads throughout the county were flooded, including several near Stone Hill Winery in Hermann.

Tornado in ST. LOUIS, MISSOURI
From 31-MAY-13 19:08:00 to 31-MAY-13 19:25:00 (CST-6)
Location: VIGUS
Tornado F-scale: EF2
Property damage: 10.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado crossed the Missouri River from St. Charles County into St. Louis County just south of Interstate 70.  As it moved through the Riverport area, it caused major damage to one of the buildings at Hollywood Casino.  Part of the roof and most of the siding were torn off of a section of the casino that housed maintenance and staff offices.  Five large power poles were snapped off at the base. The damage in this area was rated EF2.  Also, numerous trees were snapped off.  Further to the east in the Riverport area, a gas station lost part of its canopy and a nearby hotel sustained minor roof damage as well as several windows blown out.  The tornado then crossed Interstate 70 into the Earth City area.  As it crossed the highway at the intersection of I-70 and Earth City Expressway it knocked down the large steel truss that holds signs for the east bound side of I-70 into the west bound lanes of the highway.  Traffic was backed up for hours in this area due to the fallen sign and numerous power lines as well as debris laying across the interstate.  North of I-70 the tornado widened to a mile wide with the most significant damage centered just northwest of the I-70/Earth City Expressway interchange.  One warehouse building had a section of the pre-cast concrete wall collapse outward and fall onto the parking lot on the southeast corner.  Meanwhile on the north facing side of the warehouse, several bay doors were blown in and several tractor trailers and delivery trucks were blown over.  The building next door had roof damage and an unoccupied car nearby was flipped onto its roof and another one was rolled as well.   The damage in this area was rated EF2.  Further to the east and northeast, the Point 70 office building sustained extensive window damage and another warehouse had a quarter of its roof peeled off.  Spectrum Brands warehouse building on Corporate Exchange Drive had a very large section of pre-cast concrete walls collapse inward and damage here was rated EF2.  The tornado continued to the east, crossing Interstate 270 between Interstate 70 and St. Charles Rock Road.  Numerous trees, power poles and power lines were blown down across Bridgeton.  An apartment building on Natural Bridge Road lost its entire roof with some of the debris landing on cars in the parking lot.  Several other apartment buildings had minor roof damage.  Damage in this area was rated EF2.  The tornado crossed the northern portions of Lambert-St. Louis International Airport, causing minor damage to four outbuildings.  From there the tornado continued east, blowing down or uprooting numerous large trees, power poles and power lines in Berkley, Kinloch, Ferguson, and Dellwood mainly along and north of Chambers Road.  Several of the large trees fell onto houses and vehicles causing minor to major damage.  As it crossed New Halls Ferry Road it began to go in a more east northeasterly direction, paralleling Interstate 270 for a time.  A gas station at the intersection of Dunn Road and Old Halls Ferry Road had one of its canopies collapsed.   Just east of Highway 367, six power poles were snapped off along Dunn Road on the north side of I-270.  A bit further east, just east of Bellefontaine Road, an apartment complex on N. Garden Drive had eight of its buildings sustain major roof damage.   Otherwise, most of the damage in the area was to trees and power lines.  A few of the trees landed on homes causing varying degrees of damage.  The tornado then lifted and dissipated on the banks of the Mississippi River about six tenths of a mile north northeast of the intersection of I-270 and Columbia Bottom Road. The tornado caused damage to 612 homes in St. Louis County.  Five hundred and ten homes suffered minor damage, 101 homes suffered major damage, and one home was destroyed. One hundred twenty-one businesses sustained minor damage, while 5 businesses had major damage. Cleanup costs alone for St. Louis County was 4.3 million dollars.
The path length of the tornado in St. Louis County was 17.0 miles with a max path width of a mile wide.  The damage for this segment was estimated to be EF2 with max wind speeds of 130 MPH.  Overall, the entire tornado path length was 31.8 miles with a max path width of 1 mile and a maximum damage rating of EF3.

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 31-MAY-13 18:58:00 to 31-MAY-13 18:58:00 (CST-6)
Location: (SUS)SPIRIT/ST LOUIS
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in ST. CHARLES, MISSOURI
From 31-MAY-13 18:44:00 to 31-MAY-13 18:44:00 (CST-6)
Location: SCHLUERSBURG
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds blew down a large tree onto an unoccupied car that was parked at the Historic Daniel Boone Home & Heritage Center.  The car sustained major damage.

Hail in MONTGOMERY, MISSOURI
From 31-MAY-13 17:40:00 to 31-MAY-13 17:40:00 (CST-6)
Location: LIEGE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in GASCONADE, MISSOURI
From 31-MAY-13 18:00:00 to 31-MAY-13 18:00:00 (CST-6)
Location: PERSHING
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in LINCOLN, MISSOURI
From 31-MAY-13 18:00:00 to 31-MAY-13 18:00:00 (CST-6)
Location: HAWK PT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm winds blew down several power lines around town.

Thunderstorm Wind in MONTGOMERY, MISSOURI
From 31-MAY-13 17:19:00 to 31-MAY-13 17:30:00 (CST-6)
Location: DANVILLE
Magnitude: 79.00 EG
Crop damage: 0.00K
Reported by: NWS Storm Survey

Thunderstorm winds caused a wide swath of damage from about 2 miles north of Danville on Highway 161, eastward across the county to about 2 miles east of Highway 19.  Most of the damage was broken tree limbs, several large trees blown down or snapped off as well as major damage to two grain bins at the intersection of County Roads 219 and 220.  The grain bins were dented in considerably and the elevator legs had collapsed.

Tornado in MONTGOMERY, MISSOURI
From 31-MAY-13 17:20:00 to 31-MAY-13 17:21:00 (CST-6)
Location: DANVILLE
Tornado F-scale: EF0
Crop damage: 0.00K
Reported by: NWS Storm Survey

A weak tornado briefly touched down along Highway 161 from 2.5 miles south southwest to 2 miles south southwest of Montgomery City.  Much of the damage was confined to tree damage.  One large tree snapped about a third of the way from the base and fell onto a parked school bus.  No one was inside the bus.  Before the tornado lifted and dissipated, three power poles were bent about 40 degrees to the northeast.  Overall, the tornado path length was half a mile and max path width was 30 yards.  The damage was rated as EF0 with max winds of 75 MPH.

Tornado in MONTGOMERY, MISSOURI
From 31-MAY-13 17:28:00 to 31-MAY-13 17:30:00 (CST-6)
Location: NEW FLORENCE
Tornado F-scale: EF0
Crop damage: 0.00K
Reported by: NWS Storm Survey

A weak tornado touched down 2 miles north northwest of New Florence.  Much of the damage was confined to downed trees.  The tornado traveled east for about a mile.  Before lifting and dissipating, the tornado caused minor siding and soffit damage to a home and uprooted a large tree in the backyard.  The tornado path length was 1.06 miles with a max path width of 40 yards.  The damage was rated EF0 with max wind speeds of 80 MPH.

Tornado in MONTGOMERY, MISSOURI
From 31-MAY-13 17:21:00 to 31-MAY-13 17:22:00 (CST-6)
Location: MONTGOMERY CITY
Tornado F-scale: EF0
Crop damage: 0.00K
Reported by: NWS Storm Survey

A weak tornado briefly touched down about two miles south of Montgomery City along Blue Bird Road.  Much of the damage was confined to tree damage.  Before lifting and dissipating near the intersection of Blue Bird Road and Bob White Road, the roof of an old machine shed was peeled off to the south.  The tornado path length was two tenths of a mile with a max path width of 30 yards.  The damage was rated EF0 with max wind speeds of 75 MPH.

Tornado in FRANKLIN, MISSOURI
From 31-MAY-13 18:37:00 to 31-MAY-13 18:50:00 (CST-6)
Location: JEFFRIESBURG
Tornado F-scale: EF1
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down just west of Highway UU, around 3.5 miles southwest of Union.  Most of the damage consisted of snapped and downed trees and broken tree limbs. Five homes located along Indian Prairie Lane between Union and St. Clair suffered minor roof damage. The tornado lifted and dissipated just south of the intersection of Meramec Terrace Road and Indian Acres Road, around 3.4 miles southwest of Robertsville.  The tornado path length was 10 miles with a max path width of 550 yards.  The damage was rated EF1 with max wind speeds of 105 MPH.

Hail in ST. LOUIS, MISSOURI
From 31-MAY-13 19:20:00 to 31-MAY-13 19:20:00 (CST-6)
Location: ROBINWOOD WEST
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One inch hail fell in Maryland Heights.

Tornado in JEFFERSON, MISSOURI
From 31-MAY-13 19:01:00 to 31-MAY-13 19:18:00 (CST-6)
Location: BYRNESVILLE
Tornado F-scale: EF1
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down in extreme western Jefferson County near Highway NN and Apke Lane.  It moved to the east and most of the damage consisted of snapped and downed trees and broken tree limbs.  In the Byrnes Mill area several mobile homes were damaged from fallen trees.  In Scotsdale, several school buildings at Our Lady Queen of Peace Church suffered minor damage.  The tornado lifted and dissipated west of Rustic Trails Drive, around 2.7 miles east of Byrnes Mill.  The tornado path length was 12.4 miles and the max path width was 200 yards.  The damage was rated EF1 with max wind speeds of 100 MPH.

Hail in ST. LOUIS, MISSOURI
From 31-MAY-13 19:23:00 to 31-MAY-13 19:23:00 (CST-6)
Location: BURKE CITY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One inch hail fell in Florrisant.

Tornado in ST. LOUIS, MISSOURI
From 31-MAY-13 19:27:00 to 31-MAY-13 19:29:00 (CST-6)
Location: LARIMORE
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down in the Columbia Bottom Conservation Area, about 3 miles northeast of the interchange of I-270 and Columbia Bottom Road.  It uprooted a large tree in this location, then traveled to the northeast.  It uprooted another large tree just northeast of Upper Columbia Bottom Road, before turning a bit more easterly and crossed the Mississippi River into Madison County Illinois.  For this segment of the tornado, the path length in St. Louis County was 2 miles with a max path width of 50 yards.  The damage for this segment was rated EF1 with max wind speeds of 90 MPH.  Overall, the entire tornado path length was 10.6 miles with a max path width of 150 yards.  The tornado was rated EF3 with max wind speeds of 160 MPH.

Thunderstorm Wind in ST. CHARLES, MISSOURI
From 31-MAY-13 18:46:00 to 31-MAY-13 18:50:00 (CST-6)
Location: DEFIANCE
Magnitude: 74.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Thunderstorm winds snapped off several large trees in southwestern St. Charles County between Highway DD and Highway 94.

Thunderstorm Wind in LINCOLN, MISSOURI
From 31-MAY-13 18:15:00 to 31-MAY-13 18:15:00 (CST-6)
Location: TROY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in WARREN, MISSOURI
From 31-MAY-13 18:38:00 to 31-MAY-13 18:38:00 (CST-6)
Location: MARTHASVILLE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm wind blew down several large trees around town.

Hail in FRANKLIN, MISSOURI
From 31-MAY-13 18:45:00 to 31-MAY-13 18:45:00 (CST-6)
Location: WASHINGTON
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ST. LOUIS, MISSOURI
From 31-MAY-13 19:16:00 to 31-MAY-13 19:25:00 (CST-6)
Location: BURKE CITY
Magnitude: 87.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A wide swath of wind damage, just north of the path of the tornado that moved through St. Louis County extended from the I-270/Lindbergh Boulevard interchange eastward to the just west of the Mississippi River.  The most intense wind damage was to the Ramada Inn on the northeast side of the I-270/Lindbergh Boulevard interchange.  It lost about half its roof with some of the debris landing on cars in the parking lot destroying them.  More of the debris landed over two tenths of a mile away, damaging or destroying a number of campers and RVs at an RV business with a number of vehicles having 2x4s driven into them.  Another nearby hotel sustained moderate roof damage as well.  Otherwise, most of the wind damage consisted of trees blown over, numerous large tree limbs blown down, as well as power lines being blown down.  There was one injury to a hotel occupant at the Ramada Inn,  the person sustained a broken arm.

Flash Flood in CALLAWAY, MISSOURI
From 31-MAY-13 22:00:00 to 31-MAY-13 23:59:00 (CST-6)
Location: GUTHRIE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Up to four inches of rain fell in a short amount of time causing flash flooding.  Numerous roads were flooded including Highway 94.  Highway 94 was flooded in several locations.

Flash Flood in WASHINGTON, MISSOURI
From 31-MAY-13 22:30:00 to 31-MAY-13 23:59:00 (CST-6)
Location: TROUTT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to five inches of rain fell in a short amount of time causing flash flooding.  Highway 135 was flooded in several spots southeast of the intersection with Highway T for about a four mile stretch.

Hail in BOONE, MISSOURI
From 31-MAY-13 16:20:00 to 31-MAY-13 16:28:00 (CST-6)
Location: SAPP
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CALLAWAY, MISSOURI
From 31-MAY-13 16:35:00 to 31-MAY-13 16:35:00 (CST-6)
Location: FULTON
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in OSAGE, MISSOURI
From 31-MAY-13 17:38:00 to 31-MAY-13 17:38:00 (CST-6)
Location: LINN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter