This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
These big caddisflies were tempting trout as they wriggled out of their shucks, while others skated across the water at a medium pace, probably egg-laying.