Vine maple is a good choice, because they're native to the pacific NW.
How about Acer circinatum 'Monroe', which was discovered along the McKenzie river in Oregon? To about 15 ft. Looks a lot like the famous A. japonicum 'Aconitifolium' to which it is probably related. (Circinatum in general I mean, not 'Monroe' particularly.)
Lots of other maples might fit the bill. A couple of nice variegated ones that will grow to around the right size are A. x conspicuum 'Silver Cardinal' or A. rufinerve 'Albolimbatum.'
You don't say what width you're looking to fill, or any other criteria, so it's hard to know what to recommend further. There are certainly many A. palmatum to fit almost any space.
I'm in the Seattle area. Kind of looking for a tree in the back of a border to create a little privacy on one side of our yard. We need to fill in with a couple more trees and I'm trying to plant things that will add interest at different times of years (the crabapple for blooms, the smoke tree for color, etc..).
One part of the yard gets quite a bit of sun and picking a tree doesn't seem that challenging. I am mainly struggling with the shady area. It is actually next to a rhodie that is doing quite well. In the winter, its a pretty cold and shady spot.
Many maples like a bit of shade, in fact most of the small ones.
The cold is not a problem typically, especially in your climate. The trees I suggested have good interest during 3 seasons. Another to consider is A. shirasawanum 'Autumn Moon' which you might be able to find already at a decent size (if not for a decent price).
Otherwise, if you want an evergreen, how about a big Pieris, that will grow to about 8 ft?
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