It was gorgeous! It's a lenticular (lens-shaped) orographic cloud; a cloud caused by moisture-laden air rising up and cooling as it passes over mountains. We see them here all the time just east of the Rockies, and when they get all lenticular it's a very cool bonus. Orographic clouds aren't limited to the Earth you know; other planets have atmospheres with some moisture and tall mountains to overcome as well. Some people think that science takes away the romance of nature. Those people are wrong. When I lie out in the Sun and muse about the pretty clouds over my home town, I can know that what I'm seeing happens on other planets spinning around the Sun, and I'll just bet it's happening somewhere on a planet orbiting some other distant sun, lost among the billions in our galaxy. What could possibly be more romantic than that?