I hope you enjoy this highlight of my recent vacation.

I’m particularly fascinated by the fog in the Snake River Valley in the foreground. As we all know, denser, cooler air tends to flow downhill and “pool” in low-lying areas. If you take an evening or morning walk, you’ll notice that the temperature in river valleys, or even creek beds, is a few degrees cooler than it is uphill. In this video, mixing fog marks the interface between the cool and warm air. If the interface between the cool air and the warmer air above is disturbed, internal gravity waves should propagate along that interface. I believe that’s the source of the “sloshing” seen in the fog layer.