You want remote and some of the best skiing anywhere? Mount Baker Ski Area. Also has some of the best sidecountry anywhere, but you need avalanche gear and a friend for that. If you've got that, hike the Shuksan Arm. If you can handle gnarly steep spinewalls that is. Mount Baker Ski Area is small in bounds, but remote and not crowded at all, and the backcountry there is endless If you want something closer to Seattle and bigger in bounds, consider Crystal, Stevens Pass, and Alpental.
I have yet to ski in Washington but I've looked into it a lot and intend to move there at some point and those four areas (Baker, Crystal, Stevens, and Alpental) are all on the top of my list to check out.
If you don't believe me about Baker having awesome steep gnarly sidecountry, watch this, especially the second half.