Lenticular clouds (at least 4 layers) over Mt. St. Helens

What forms the "smoke rings" is the air flowing over the mountain
getting pushed up higher as it goes up and over the top.  The moisture
content and initial temperature are just right so that the moisture
condenses from a vapor to small particles at the higher altitude.
When the moving air moves past the peak and comes down again, the
particles evaporate back to an invisible vapor.  The two "pancakes"
describe that there are two layers of air for which this is happening,
thus making this awesome picture possible.

Picture (and caption?) by Brent and Jan LeBaron
Sent by Roger Smith, 11 May 2005

Note by jh: There is a dark shadow ring separating lower and upper
"shells" in each of the two main cloud structures.  To me these
indicate two embedded lenticular clouds in each structure, so there
are actually four layers with the right conditions.