A thick, heavy, wet snow, combined with high winds, promises cascading travel delays both on the ground and in the air, as well as power outages that will likely spread across the Mid-Atlantic and Northeast. As of 8 a.m. New York time, 6,564 flights into and around the U.S. had been cancelled, with New York, Newark, Boston and Philadelphia among the hardest hit, according to FlightAware. New York subway trains may run with delays and the Long Island Railroad will run on a weekend schedule Monday, Metropolitan Transportation Authority chairman Janno Lieber said.