Blizzard warnings blanket the Northeast Monday as a beastly winter storm is snarling travel and pounding millions with heavy snow.Threat level: In hard-hit areas, travel will be "extremely treacherous," forecasters say, and some leaders are restricting it. Meanwhile, more than half a million customers in Massachusetts, New Jersey, Delaware, Rhode Island are without power.The latest: The National Weather Service predicted Monday morning that heavy snowfall rates and gusty winds will keep batterin...