Yay: University of Washington has Operating Systems graduate programs
Yay: U of W is in Seattle
Boo: Application deadline was 15 Dec.
Boo: No applications accepted for spring semester
Boo: I haven't taken the GRE.
I emailed the department outlining my situation, and indicated that I just recently decided that I would enjoy doing OS research. Have yet to hear back from them. I expect that they'll tell me to take the GRE and apply next year.