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.
Keying this one out using Zloty & Pritchard 1997:
-No ganglionic markings on sternites 2–8
-Posterior margins of sternits 6–8 without numerous spines
-Mesal gill extension well developed (I really don't like the "well developed" language when it's subjective, but in this case the other option doesn't lead anywhere productive)
-Tails pale in basal 1/3
-Larger species (13–16 mm) — this one is just shy of 12 mm, but closer to 13 than to <10
This all points to Ameletus vernalis.