The Seattle Times wrote a great piece about the look of the 2020-21 ski season. Adding another great outdoor activity to the list will be certainly nice, but restrictions will be a significant part of all plans. Most ski/snowboard areas will require season tickets or single-day advanced ticket purchases.
Crystal MountainOpens: Nov 20thInfo: Limited capacity and no walk-up tickets. You must pre-purchase tickets or have a season pass.
Steven's PassOpens: Dec 4thInfo: Limited capacity prioritizing season ticket holders. Single day tickets will be pre-purchase only.
The Summit at SnoqualmieOpens: TBAInfo: No restrictions currently planned other than govenment mandated occupancy.
Mount BakerOpens: Nov 26 (snow permitting)Info: Working on restriction policies, reservations for busiest days, and limited capacity are all likely.
Again, for more depth on the subject, check out this article.