Lenticular clouds are lens-shaped clouds that often form in the vicinity of mountains. They can form over other large structures as well, when these barriers are oriented perpendicular to the direction of the incoming wind. If the air is stable (meaning, not rising or falling vertically on its own), when the fast moving air encounters the barrier or mountain peak, it is forced upwards. This forced upward movement can generate a series of waves downwind of the mountain, called “gravity waves.” Lenticular clouds are the clouds that form in the peaks of these waves.
If there’s enough moisture in the atmosphere surrounding this barrier, when the air is forced upwards, it saturates and begins to condense water. This forms the clouds that you can see with your eye. When the air moves downwards towards the trough of the wave, the water evaporates, leading to clear sky. That’s why you can often have a series of lenticular clouds over and downwind of the mountain — they are showing you the peaks of those gravity waves.
Since the air is moving very quickly, and the mountain or barrier remains stationary, these clouds are actually continuing to develop in the peaks (and dissipate in the troughs ) of the wave of the wave. That’s why lenticular clouds often don’t move horizontally in the sky. They can remain parked over a barrier for several hours. They are most common in the winter and spring when the winds aloft are the strongest.
These clouds are often mistaken for UFOs, since they look like flying saucers. I personally think they look more like stacks of pancakes. While they may be pleasant to behold, these clouds are often an indication to pilots that strong winds and turbulence are present in the atmosphere. Without these clouds, those gravity waves would otherwise be invisible!