The North Face Women's Runaway Insulated Skirt---I know we didn't want to do the skirt awhile ago, but I think it actually has a practical use. Throw it on over long underwear and you've got a street style combined with warmth and your ski clothing.
There are plenty of insulated jackets and pants to choose from out there. Why not skirts? The Thongmu Skirt is long, and quilted, and insulated. The fabric is water-resistant and windproof; and the PrimaLoft® One insulation keeps you cozy even if it gets wet. The whole thing compresses down into something you can stow in your purse. When the temperature drops, slide it over whatever you're wearing.