The Seattle area's largest umpire association is the Northwest Baseball Umpires Association. They maintain a website at:
http://www.NBUA.com
I'm sure they, like most umpires associations, can use an experienced, qualified and talented umpire. Bring letters of recommendation from your trainer and assigner. Letter's from coaches help as well.
But don't expect to be taken solely at your word. I believe the NBUA evaluates transfers closely to confirm the recommendations. You can't believe the number of mediocre and below umpires who transfer in to an association claiming to be Top Dogs and D-1 qualified. Those of us responsible for assigning need to know the REAL level of competency before we give new umpires a schedule.