National Weather Service Weather Forecast Office

http://www.srh.noaa.gov/tsa/?n=weather-event_2015mar25

Severe thunderstorms developed late in the afternoon on March 25, 2015 near a warm front that had surged north into northeast Oklahoma and northwest Arkansas. With a highly sheared and unstable air mass in place across the area, discrete supercells were able to develop near the warm front late in the afternoon and into the early evening hours. Several tornadoes were spawned from the supercells from west of Tulsa into northwest Arkansas. As the evening wore on, a cold front surged into the area from the northwest and thunderstorms congealed into a line along the cold front marching to the south and east during the evening and overnight hours.