That is wild.
What you are probably looking at is lenticular clouds that are being disrupted by thermals from the ground. As the hot air rises (it is turbulent) it meets the the laminar flow of upper air. This upper air is in waves. You can see it in the areas of the clouds that are smooth. These waves are formed by high speed air blowing across a mountain range. If you could see the top of those clouds they would be smooth and rounded.
We glider pilots live for mountain wave. You can go to great altitude in them. I have been to 25000 feet and this is not considered high for a mountain wave flight.