The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
I'm not fully confident in the ID on this one. I couldn't see for sure that there are two equal pads under the tarsal claws instead of three, but it seems that way. The antennae are 4-segmented, although I'm not sure if the last segment counts as a "segment" rather than a style@ or arista sticking off the third segment. It has three ocelli. The key characteristics generally point to Empididae except "Vein R4+5 usually branched." That vein certainly isn't branched in this specimen, but the key does say "usually."
This true fly was collected from the South Fork Snoqualmie River in Washington on May 22nd, 2022 and added to Troutnut.com by Troutnut on May 24th, 2022.