The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I didn't key this one out under the microscope, but I just keyed a similar one from Montana and this one matches the macroscopic appearance closely enough that I'm guessing it's the same thing.
This stonefly was collected from Mystery Creek #249 in Washington on July 4th, 2020 and added to Troutnut.com by Troutnut on July 12th, 2020.