Lenticular clouds (a.k.a. Orographic clouds) form over mountains due to warmer, uprising air. The technical name for these clouds is: altocumulus standing lenticularis. Lenticular means "lens shaped". They normally align at right-angles to the direction of the wind.
As a note of interest, sailplane pilots look for these types of clouds because they indicate a long series of standing wind waves. These kinds of winds can take a glider to great altitudes and for long distances. I have a friend, Cecil Craig, who flew a glider 268 miles in 1967 from Mt. Rainier in Washington to Crater Lake in Oregon by following a series of these winds over the Cascade mountain range. He broke a few world records with that flight!
This photo was taken in Colorado at Keystone Ski Resort, Breckenridge Resort can be seen far in the distance.