I wouldn't think that an 18" wheel would be a good choice for serious winter driving. Generally the lower profile the more snow the tire will need to push. I run 16" in the winter.

Farthest North modded TTQC in all the world.... Borla, Forge 6 (washer modded )DV, ABT Chip, Bilsteins, UUC springs, Neuspeed rear bar, SFC Sunroof, Bird armrest, Euro mirrors, shift light, 3M headlight protectors, TT stem caps, black front Audi rings, mud flaps, Invica-Shield on front, Yokos in winter, cedar bed, Westie, S4 (Tip) (In reserve)PS2 for training, DenBo shift boot conversion, MKI front end (re-installed), Raffi shift knob, shift ring badge, gauge pack, 3.2 type rear valance, TTDA , DG Sigma, Mintex Reds, MoFo, Schwing Thing Cupholder, Boost Machine, DEFCON"s on shelf. ModShack grab bar. No Mo Mods, unless they have purpose, or unless Steve tells me I need them.