this is a region in which cold air clashes with warm air. While there does tend to be a strong temperature gradient along fronts in the plains this explanation only touches the surface to why tornadoes are common in the plains.
A tornado requires a parent thunderstorm. Thus, an environment conducive to tornadoes must also be conducive to thunderstorms. Thunderstorms are much more common in certain locations. Thunderstorms are not nearly as common to the west of the plains as they are across the plains and to the east of the plains. The Gulf coast region has the most thunderstorms.
