Here's a couple of alternatives for you.

Check with Twin Bridges Marina in Anacortes. 360-466-1443. It's a ways out of
Seattle, but the advantage is that you are 90% of the way to the San Juans when
you get to your boat. This is a rack storage place, so your mast might be a
problem unless it can be unstepped, and your draft might be a problem also. If
they can't help you out, they might know who can.

Down in Tacoma, the old Pick's Cove facility has just been acquired by the same
people that run Elliott Bay Marina in Seattle. Class act. They are doing indoor
storage, and some of it may not be "rack" style. Call Tim Curry down there, at
253-627-4344