The storm environment for May 20th involved a very unstable atmosphere, especially across the northern third of Northeast Texas, Southeast Oklahoma and Southwest Arkansas. The atmosphere was weakly capped which resulted in the development of scattered severe thunderstorms across the region. An upper level disturbance moved across the region as well and with cold temperatures aloft resulting in steep mid level lapse rates...a majority of the storms produced large hail. High shear was also in place in the mid and lower levels of the atmosphere which provided a wind threat as well. Some of these storms produced tornadoes across the region.

Hail in SMITH, TEXAS
From 20-MAY-11 15:54:00 to 20-MAY-11 15:54:00 (CST-6)
Location: TYLER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in RED RIVER, TEXAS
From 20-MAY-11 16:14:00 to 20-MAY-11 16:14:00 (CST-6)
Location: DETROIT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in HARRISON, TEXAS
From 20-MAY-11 17:20:00 to 20-MAY-11 17:20:00 (CST-6)
Location: HALLSVILLE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in HARRISON, TEXAS
From 20-MAY-11 17:20:00 to 20-MAY-11 17:20:00 (CST-6)
Location: LONGVIEW HGTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail reported on the eastern side of Longview just in Harrison County.

Hail in CASS, TEXAS
From 20-MAY-11 19:05:00 to 20-MAY-11 19:05:00 (CST-6)
Location: SPRINGDALE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Tornado in HARRISON, TEXAS
From 20-MAY-11 17:38:00 to 20-MAY-11 17:45:00 (CST-6)
Location: WALKERS MILL
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The National Weather Service conducted a storm survey in Harrison County and concluded that damage was the result of an EF0 tornado.  The tornado first touched down over a wooded area along Young Road snapping a few small trees and limbs.  The tornado crossed Hickey road and Fire Tower Road where a few trees were snapped and uprooted.  The tornado tracked northeast crossing Noonday Road snapping a few trees.  The tornado ended along hwy 154 west of Nesbit snapping a few trees.  A video of the tornado was provided to the NWS as evidence from a storm spotter near Nesbit.  The Maximum winds are estimated at 65-70 mph.

Thunderstorm Wind in HARRISON, TEXAS
From 20-MAY-11 21:15:00 to 20-MAY-11 21:15:00 (CST-6)
Location: WALKERS MILL
Magnitude: 53.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A large pine tree fell on a home northeast of Hallsville, Texas.  There were no injuries reported with this event.

Tornado in RED RIVER, TEXAS
From 20-MAY-11 16:36:00 to 20-MAY-11 16:38:00 (CST-6)
Location: MANCHESTER
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The National Weather Service conducted a storm survey in Red River County and concluded that damage was the result of an EF0 tornado.  The tornado first touched down over a wooded area east of Manchester damaging a few trees.  The tornado moved northeast crossing FM 195 where a few small trees were snapped and a few small trees and limbs.  The tornado ended north of FM 195.  The Maximum winds are estimated at 65-70 mph.