One word. Brrrr. This week, an Arctic air mass is heading south through the central U.S., bringing some seriously cold weather, with record-breaking low temps likely. Expect sub-freezing temperatures to stretch all the way down to the Gulf Coast. On top of that, heavy snow is moving from the Rockies today, heading across the central Plains, Ozarks, Tennessee Valley, North Carolina, and into the southern Mid-Atlantic states by Wednesday.