BugGuide helped ID this one: This species is common across the DC area and differs in a few traits from the closely related linnei (often difficult to qualify). In this case, the coloration (esp. pronotal characters), eyes (slate-greenish), broad appearance and distribution of the silvery pruinosity are all charateristic of a quasi-teneral winnemana. This species and the very similar looking Tibicen linnei are also known to hybridize.
Seen on a sidewalk in urban Washington, DC. I moved it to the grass.