Originally Posted by
Daze
The Amtrak Empire Builder has been having significant operational problems and operates hours late virtually every day, so do not plan on any kind of close connection at Seattle.
That was my thought, too. I assume the OP isn't going to try for the 3:10 p.m. flight on the 5th. That would be virtually impossible. There's a 6:50 p.m. flight that is more likely but by no means a sure thing.
FWIW there are hotels within walking distance of the Sea-Tac airport terminal, so one option would be to take light rail out to the airport in the afternoon/evening and stay overnight there...which would put you in good position for catching the first flight up to KTN the next morning.