A large upper level trough of low pressure was observed across the Central Plains. A disturbance in the broad upper level trough, combined with an outflow boundary moving north into central Missouri, helped produce severe thunderstorms across central Missouri, during the afternoon and evening hours of May 20, 2013. A super cell severe thunderstorm produced an EF1 tornado in Pettis County, where minor damage was observed. Hail and wind damage were also observed, along with some flash flooding.

Flash Flood in PETTIS, MISSOURI
From 20-MAY-13 18:02:00 to 21-MAY-13 00:02:00 (CST-6)
Location: HUGHESVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: State Official

Several feet of water was reported over the road, near the intersection of Highway D and McGruder Road.

Hail in RANDOLPH, MISSOURI
From 20-MAY-13 17:15:00 to 20-MAY-13 17:15:00 (CST-6)
Location: MILTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in JOHNSON, MISSOURI
From 20-MAY-13 15:55:00 to 20-MAY-13 15:56:00 (CST-6)
Location: KNOB NOSTER
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A supercell thunderstorm intensified as it moved into eastern Johnson County, near Knob Noster. Strong, straight-line winds estimated up to 60 mph, caused some minor damage to a house and mobile home.

Hail in CASS, MISSOURI
From 20-MAY-13 14:45:00 to 20-MAY-13 14:45:00 (CST-6)
Location: HARRISONVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in JOHNSON, MISSOURI
From 20-MAY-13 15:20:00 to 20-MAY-13 15:20:00 (CST-6)
Location: HOLDEN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flash Flood in PETTIS, MISSOURI
From 20-MAY-13 17:51:00 to 20-MAY-13 23:51:00 (CST-6)
Location: DRESDEN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: State Official

Several feet of water was reported over Rieckhoff Road near State Highway T.

Hail in PETTIS, MISSOURI
From 20-MAY-13 15:26:00 to 20-MAY-13 15:26:00 (CST-6)
Location: SEDALIA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in JOHNSON, MISSOURI
From 20-MAY-13 15:35:00 to 20-MAY-13 15:35:00 (CST-6)
Location: WARRENSBURG
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SALINE, MISSOURI
From 20-MAY-13 16:30:00 to 20-MAY-13 16:30:00 (CST-6)
Location: MARSHALL ARPT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in COOPER, MISSOURI
From 20-MAY-13 18:40:00 to 21-MAY-13 00:40:00 (CST-6)
Location: BUNCETON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

State Highway J was closed due to high water.

Hail in CASS, MISSOURI
From 20-MAY-13 14:22:00 to 20-MAY-13 14:22:00 (CST-6)
Location: LISLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CASS, MISSOURI
From 20-MAY-13 14:15:00 to 20-MAY-13 14:15:00 (CST-6)
Location: DREXEL
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in PETTIS, MISSOURI
From 20-MAY-13 15:57:00 to 20-MAY-13 16:16:00 (CST-6)
Location: LAMONTE
Tornado F-scale: EF1
Property damage: 20.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A supercell thunderstorm intensified as it moved into east Johnson County, MO near Knob Noster. Initially, strong, straight-line winds created minor damage in Knob Noster. As the storm continued to develop and move northeast, a tornado formed about 4 miles west-southwest of LaMonte, in extreme western Pettis County,  at about 357 PM CST. The tornado, EF0 to EF1 at times, continued from this point to the northeast for approximately 14.5 miles, damaging numerous farm out-buildings, including two large chicken farms, before dissipating around 416 PM CST, around 2 miles north of Hughesville.  Numerous trees also suffered damage.