Much of the United States will either get a White Christmas or a bitterly cold one, as the forecasts for the country see snowstorms and temperatures in the deep south as low as the 20s. Forecasters are warning of treacherous holiday travel and life-threatening cold for much of the nation as an arctic air mass blows into the already-frigid southern United States, with experts predicting the 'coldest Christmas in years.' The coming week has the potential for 'the coldest air of the season' as the strong arctic front marches across the eastern two-thirds of the country in the days before...