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.
Hyun Kounne generously provided photos of the striking, hard-to-find Heptagenia culacantha from the mainstem Delaware River. She mentioned it was one of maybe half a dozen she saw on the water that day.