Anthomyzidae was my first thought when I saw this fly, but I had for some reason decided that was incorrect. Using Rohacek & Barber 2016, this keys out to Anthomyza oblonga, which seems to be common across much of the Eastern US and Canada, though no records south of North Carolina.

The gonostylus is somewhat elongated and ends in a sort of weakly concave tip for this species, compared to the broader shape in A. silvatica & A. tenuis. These three form the "A. macra group" in the Nearctic, recognized by lacking white microtomentum on the occiput and having yellow pleural sclerites. Other useful traits for diagnosing the genus: ctenidial spine on profemora, wings hylaine, legs yellow, three orbital bristles (anterior bristle quite small).

Roháček, J. and Barber, K.N., 2016. Nearctic Anthomyzidae: a monograph of Anthomyza and allied genera (Diptera). Acta Entomologica Musei Natioalis Pragae, 56.