I shot these while up in the hills of Hood River county, looking north. Based on maps and my personal experience with Mount Adams, I think the fire started at one of a series of campgrounds in that area, either Cold Springs, Morrison Creek or Horse Camp. Mayhaps someone left a campfire unattended?
This was about 45 minutes ago... I can see the mountain from my house, and while I can't see the base where the fire is burning, the plume is at least twice as big now.
The Snoregonian is finally on it, in its typically awkward prose.