I am glad that this was repeated - since I missed it the first time. Surprising though that APOD does not have a longer institutional memory, for there are not likely that many people (all of whom are appreciated by us!) involved, and this is a striking image.
Except for sailplane pilots, no one wants to be in that picture, for though the clouds are beautiful, and look calm, this would not be a good day to be flying over or immediately to the east of the Cascades as there would be severe turbulence - which gliders simply call "lift".
The mountain (A "mountain" is any really big pile of dirt with notable relief - n.b. one can only claim pedanticy (sorely needed neologism) if one is correct: To paraphrase a current politician "Volcanoes are mountains my friend!") is about 14,400 feet (~4,390 m) high. As you can see, the bases of the lennies are that altitude or more. The contrails are probably ~30,000.
Mt Rain is one of the most beautiful, and most dangerous, volcanoes in the world. It is dangerous because it is thickly coated with glaciers, is still active, and is just up a river from Seattle. When Mt Rain erupts the resulting lahar (slurry of lava, ash, rocks and melted glaciers) will fill that river valley in the same manner as did the eruption of Mt Rain's sister - Saint Helens - a few years ago (which eruption was visible from Seattle).
We can hope all we want, but Mt Rain will erupt again and now is the time to take steps to ameliorate the damage this will cause. However, as with climate change, I doubt that any meaningful action will be taken until the disaster has occurred.
Still, a beautiful picture of an interesting phenomenon.