This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
Described by Kondratieff, B.C. & Kirchner, R.F. (1988) A new species of Acroneuria from Kentucky (Plecoptera: Perlidae) and new records of stoneflies from eastern North America. Journal. Kansas Entomological Society 61, 201–207.