If the temperature at the crest of one of the air waves reaches dew point, lenticular clouds can form. ... These often produce precipitation, and the two I've experienced so far have both rained on me, rather violently.

What weather is associated with lenticular clouds?

Lenticular clouds are a visible sign of mountain waves in the air. However, these waves can be present beyond the clouds, and may exist even when no clouds are formed. On the ground, they can result in very strong gusty winds in one place, with still air only a few hundred metres away.

What do lenticular clouds indicate?

Lenticular clouds indicate great instability in that layer of the atmosphere, and form in areas of mountain waves. Like ocean waves, these waves of air bouncing over the mountains are anything but stable. It makes sense that it would be a "rough ride".