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 Frison, T.H. (1942) Descriptions, Records and Systematic Notes Concerning Western North American Stoneflies (Plecoptera). The Pan-Pacific Entomologist 18, 9–16.