If by chance you have not seen news on Amtrak
Yesterday service between Portland and Seattle was suspended with no alternative to travel other than special fares on Horizon Air being offered. Interstate 5 is closed for a 20 mile stretch near Chehalis and Centralia. All three mountain passes were closed as well. So presently air is the only option.
Additionally it was announced that rail service between Seattle and Vancouver was suspended with alternative transportation (whatever that means) being utilized.
Whether there will be a reinstatement by Monday will depend upon how much the floods subside and the amount of damage discovered.