Recently there have been some 'close but not quite' Kelvin-Helmholtz clouds. These look pretty certain to me, but what do I know? The conditions were right - the clouds are moving from NW to SE and passing over the Blue Ridge mountains which run from 5,000 - 6,000 along this stretch of the Blue Ridge Parkway.

Nikon D750, Nikkor 24-120mm ND0.8 grad filter

very minimal...