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. (1935) New North American species of the genus Alloperla (Plecoptera: Chloroperlidae). Transactions of the American Entomological Society 61, 331–344 + Pl. XI-XIV.