Wall cloud

Wall clouds (or pedestal clouds) are localized, large and persistent lowering cloud formations that develop below the rain-free region of thunderstorms. Rotating wall clouds are indicative of mesocyclones in thunderstorms. Wall clouds do not always rotate, though.

Wall clouds with lightning and rain

Wall clouds are formed by a process known as entrainment, when an inflow of warm, moist air rises and overpowers rain-cooled air during a downwind downdraft.