The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I'm guessing this is Rhithrogena virilis based on resemblance to a similar specimen collected last year.
This mayfly was collected from the South Fork Snoqualmie River in Washington on June 16th, 2018 and added to Troutnut.com by Troutnut on June 23rd, 2018.