Ellison et al. (2012, Field Guide to the Ants of New England) separate Formica glacialis and F. podzolica in couplet 14 of their Formica key (p. 140). Main separating character is the presence/absense of hairs on promesonotum.
This distinction between the 2 species is qualified in such a way that it is likely of little use:
"Promesonotum usually lacking hairs; ...... F. glacialis"
vs,
"Promesonotum usually with erect hairs; ... F. podzolica"

The secondary character state in the couplet may be more useful but it is also subjective:
"dense silvery pubescence on segments 1-2, fading on segment 3;... F. glacialis"
"silvery pubescence prominent on segments 1-3; F. podzolica"

My comments may seem unjustly critical but they are not. The key simply emphasizes the real difficulty of separating these 2 species.

The above image shows the gaster of what I interpret as Formica podzolica; compare it with F. glacialis: