The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I'm calling this one Cinygmula just based on the general look and the fact that the genus is very common in this river. Official keys can't rule out other Heptageniidae, though.
This mayfly was collected from the South Fork Snoqualmie River in Washington on June 16th, 2018 and added to Troutnut.com by Troutnut on July 3rd, 2018.