In the morning the bird seemed to prefer the riverbanks from the Route 318 bridge and immediately southward to the post office. Both west and east banks were used (mostly the sunlit west side), often foraging quite low...even on the ground at times. Later in the morning, as temps warmed up, it went a bit higher, and for several minutes it was seen foraging in the evergreens at the NW corner of the 4-way intersection that is immediately on the west side of the bridge (318 x 181/West River Rd).
As Dave mentioned in his initial report, this is likely a young male. It shows no signs of hybridization with Townsend's Warbler to my eye - the breast completely lacks yellow, it is only faintly marked on the rear auriculars, and the upperparts are gray with an olive tinge.
A huge Thank You and Congrats to Dave Rosgen for the great find, a second state record if accepted by ARCC.