From today’s Earth Science Picture of the Day:
Looks like a weather guy over at Warren Wilson took a series of photos of a lenticular (lentil- or lens-shaped) cloud and made them into an animated GIF. These clouds are seen fairly often here, where they frequently form over mountains.
Click here to see the adjective for clouds that form over mountains.
I see these clouds a lot from the parking lot of the community college where I tutor math. Great mountian views from there.