The clouds are thinning over the Northwest and the biggest improvement is along the coast. Here is the latest visible image at 11:40 AM:
There is an enhanced area of showers going into the Washington coast, but that will be through by 3 PM. I am encouraged that the showers are suppressed offshore. If you are on the coast...go ALL the way to the coast...to the waterline...should be less clouds there. Any there will be clouds and sun..so you can see the transit in the gaps. Eastern Oregon seems to be opening up now as well.
Weak convergence is keeping the central Sound cloudy with some showers...these should lessen during the afternoon but still should be a problem. The latest 4/3 km WRF run also suggest that the Sequim/N. Whidbey island/San Juan area should be open, and perhaps the far south Sound (e.g., Olympia). In fact, the area south of Tacoma, might be a good bet if you want someplace close to SEA...it is in the lee of the Olympics.
Good luck...this is an extraordinarily rare astronomical event.