The Federation of Fly Fishers of washington has there annual expo in Ellensburg. It will be two days. I don't think there is a fly tying contest but you will be able to see some of the best tyers in the area there. Google FFF ellensburg you will find all the info. I will be there it is a blast.
Here's the link to the FFF event. It is April 30 & May 1st in Ellensburg. There's no fly tieing contest but there will be 80-100 demonstraion tiers including several from WFF. In addition, there will be Fly Tying Classes, Fly Casting Classes and Free Fly Casting Clinics, Free Seminars, Free Fly Fishing 9 Hole Course, Free Youth Fly Tying Tables, Raffle and Auction, BBQ Dinner/Banquet. The featured fly tier will be Skip Morris and the featured fly caster will be Brian O’Keefe.
General admission is only $5.00 (covers both days). Admission is free for FFF members and youth under16. Parking is free and there is inexpensive on-site RV and Tent Camping!