I’d much appreciate help figuring out what kind of spider this is. I’m in Western Washington, in the northern suburbs of Seattle. Its outside, on the eaves of the house. Particularly wondering if a yellow sac spider.
Interesting! The size, shape and posture, as well as the visible patterning on the body, are all reminiscent of Dolomedes tenebrosus, the common terrestrial fishing spider here in the east. However, there are a couple of odd things here: 1. Dolomedes is a genus only found (as far as I know) in the eastern half of the US, 2. The abdominal color pattern is a bit off from what I would expect (dark flank marks at the front of the abdomen, especially), and 3. That looks like an egg sac the spider is sitting on top of, as if it was guarding, but fishing spiders (as far as I know) do not make egg sacs like that - they make ball-shaped egg sacs which they carry around with them using their fangs to hold them.
The thing is, nothing else rings a bell with me - the only other large wandering hunter that would be anything like that in the Pacific NW, that I know of, is the Giant Crab Spider Olios giganteus, which doesn't look much like that, although it does make a silken retreat/egg sac protection.
I confess that I am stumped, although I can confidently say that it is not a Yellow Sac Spider.
However, I can suggest two good options for identification: the Burke Museum: https://www.burkemuseum.org/collections-and-research/biology/arachnology-and-entomology/contact-form
and Bug Guide: https://bugguide.net/node/view/6/bgimage
both of which can often do identifications from photos alone (although with spiders, this can sometimes be tricky). Good luck!