I lived in Bellingham for a few years in the mid-90’s. I used the gym at WWU. And I used to go climb the twin sisters for vertical (ski tour in winter) glacier travel is relatively minimal. Also used to run in and climb the fisher chimneys (to the top of the chimneys) on shuksan, but obviously that’s a summer/fall thing. I did a lot of running and ski touring around mt baker in all seasons. Summer is pretty self explanatory, but in winter keep in mind that the south side of baker is open to snowmobiles so you can actually use their tracks get pretty quick access on that side. I once followed snowmobile tracks to the summit (waaay inside the wilderness area). I disliked the Chukanut drive stuff because it was always either muddy and/or too many (dangerous!) roots.
I also used to go up to Grouse Mountain for skinning and xc skiing and Squamish (on foot, rarely snowy at that elevation) and Whistler (on skis in winter and foot in summer). The trail up the Squamish chief is steep! Obviously I had a lot of time back then 😉
Hope some of that helps. There would also be some steep terrain around Darrington, but obviously that’s mostly summer/fall.