A powerful and potentially dangerous winter storm is threatening millions of americans, and it could disrupt travel during this busy holiday week. windchill alerts stretch from the canadian border to the gulf of mexico. look at this map. cnn is live in denver. which could see temperatures plummet by as much as 60 degrees by tomorrow morning. so i see the hat. i see the vest. it's not too cold yet, but how are folks there keeping warm? >> reporter: yeah, that's right, victor. we're not feeling it yet. it's about 50 degrees as we speak, but that bitterly cold arctic blast is quickly approaching....