I was waiting at the traffic light in town when I looked over to my right, above mailbox peak. What I saw was a very small, "U&quo

I was waiting at the traffic light in town when I looked over to my right, above mailbox peak. What I saw was a very small, "U" shaped cloud-like object. It had sharp points at the top, and was thicker at the bottom, almost what you would expect a dramatic meteor to look like. It was moving so slowly that I at first thought it was a stationary cloudlet. As I continued to look, I noticed it steadily closing the gap between itself and the horizon, and it disappeared over the mountain.. Never seen anything like that before, but I would love an explanation.