Without really digging into this, the ageostrophic flow has a significant easterly component which should act to warm the boundary layer well above freezing, in those areas IMO. The coastal low gets going too late to prevent that, as I see it. Zooming out, I think the surface front has that classic “kink” look following the northern Apps, where we get significant cold air damming down to BDL but mid to upper 30’s points East, up to BOS. That’s my thoughts for now anyway.
Regardless I agree, sig ice is the big threat, with highest confidence from BDL to ORH.