This one pretty clearly keys to Kogotus, but it also looks fairly different from specimens I caught in the same creek about a month later in the year. With only one species of the genus known in Washington, I'm not sure about the answer to this ID.
I am a 67 year old retired English reacher from Florida. I retired to Townsend, Tennessee in September of 2017 for a more peaceful existence and for the excellent (though difficult) fly fishing in the Smokies. I spend most of my time fly tying, fly fishing, and playing the 5-string banjo.