The North Fork Preservation Association website says… All that smoke in the North Fork today is from the Copper King Fire near Thompson Falls in the Lolo National Forest. The blaze has been burning in high, rugged terrain for better than three weeks. Dry, windy conditions added several hundred acres to the fire since yesterday (it’s now at 6908 acres officially) and brought some of the smoke up here. Read the full story here.
There is also a video forecast from KPAX.com about this fire.
Some of the smoke could also be from the Lakeside fire. Read about that in the Flathead Beacon.