Weather-Related

Lenticular clouds, technically known as altocumulus standing lenticularis, are stationary lens-shaped clouds that form at high altitudes, normally aligned at right-angles to the wind direction.

These clouds are formed by so-called "mountain waves" of air created by strong winds forced over high mountains.  Then they hang over the mountains like alien "motherships."  Mount Rainier in Washington is famous with weather aficionados for producing some of the most spectacular lenticulars.

See a gallery of lenticular clouds at DarkRoastedBlend.