Northeasterners are stocking up on food and water as they prepare to be slammed with up to three feet of snow Friday. The potentially record-breaking storm is slated to move in on New York City, Boston, and other parts of New England on Friday morning, with the heaviest snowfall expected at night and into Saturday. New York City Mayor Michael Bloomberg is ready with plows and 250,000 tons of salt on standby for the 10 to 12 inches the city could receive, and coastal areas still dealing with the ramifications of Hurricane Sandy are bracing for yet another power outage. Meanwhile, schools in Boston; Providence, Rhode Island; Hartford, Connecticut; and elsewhere in New England called off school Friday, and 2,600 flights were canceled through Saturday in preparation for the snow.