June 2022 - Undular Bore (June 10, 2017)
The roll cloud in this scene is an undular bore. This undular bore developed when the (shallow) leading edge of a cold frontal zone impinged on (deeper) cool (but not cold) air generated by precipitation from an earlier thunderstorm. The kinematic and thermodynamic properties responsible for the cloud were maintained well off to the east; as the bore translated at roughly the speed of the front through the cool air.
Plate 1. Undular Bore. Captured on June 10, 2017 at 8:33am CST. Looking north from 47.95°, -96.96°.