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.
Described by Kondratieff, B.C. & Voshell, J.R., Jr. (1979) A new species of Diploperla (Plecoptera: Perlodidae) from Virginia. Annals of the Entomological Society of America 72, 451–453.