I love lenticular clouds, and used to see them all the time over the Owens Valley of California. This photo was taken by Richard Hahn, who describes it along with co-author Jim Foster:
The photo above showing a phenomenal display of lenticular clouds was observed near Estes Park, Colorado on the evening of January 5, 2012. I was on the south side of Deer Mountain in Rocky Mountain National Park when the setting Sun lit up the western sky in shades of copper and tangerine. Lenticular clouds are a type of wave cloud that typically occur on the lee side of mountain ranges and form when air is forced upward as it moves over higher terrain. In winter, these clouds are often accompanied by downsloping winds ushering in warmer weather to the Front Range of the Rockies. The lack of snow in the foreground is evidence of prior downsloping and of the relatively warm, dry conditions that have prevailed in Colorado during the early winter. Photo taken at 5:02 p.m.
To see this in all its splendor, click to enlarge:
h/t: Diane G.