Rare cloud formation wows onlookers

Video courtesy Amy Christie Hunter/CNN

(CNN) -- A rare formation of clouds wowed onlookers at Virginia's Smith Mountain Lake on Tuesday.

The photo shows Kelvin-Helmholtz Waves, which the National Weather Service defines as, "Vertical waves in the air associated with wind shear across statically-stable regions. Can appear as breaking waves and as braided patterns in radar images and cloud photos."