SEATTLE - Mountain waves are rolling waves of wind caused from air blowing over the tops of mountains. But depending on the strength of the wave, in some scenarios, it can make Cascade wind storms even stronger, as was the case last week.
In our case, aside from the wind rushing through the gaps in the mountain passes between eastern and western Washington, we had strong winds rolling over the tops of the Cascades. The wind was so strong, that after pushing over the mountain crests, there were huge waves of air rolling down the west side of the Cascades, causing even stronger wind gusts.
You can visualize this by thinking of the thunderous crash created after a large wave of water crests on the ocean. Only in this case, it's a "wave" of air.