Snoqualmie Pass is usually good by March/April. Astronomical twilight ends out there before 9 pm up to March 27th, so that could be a good time.

I'm an avid hiker/backpacker who lives in Spokane and I love living out here largely because of the access to the outdoors. Lots of good hiking immediately surrounding Spokane (although not necessarily what I'd consider destination hikes for someone from the west side, unless you're looking for something that's not the Olympics or Cascades) and then northward to the Salmo-Priest wilderness. If you can find the time from late June through September, I highly recommend Abercrombie Mountain and/or the nearby Salmo-Priest. Wildflower season up there is mid- to late July.