Thousands were without electricity across the South as a powerful winter storm moved across the eastern U.S., snarling air and ground traffic and threatening heavy snow for Northeastern cities including New York.

Across the U.S., 2,985 flights were canceled as of mid-morning Wednesday, including two-thirds of all arrivals and departures at Hartsfield-Jackson Atlanta International Airport, said FlightAware, a Houston-based tracking service. Amtrak said it scrubbed some long-distance train service into the U.S. South.

More than a half-dozen flights between Seattle and Atlanta were canceled Wednesday. Atlanta is one of the world’s busiest airports, and flight problems there can ripple through the U.S. (and international) air system.

New York and Philadelphia might receive 10 inches of snow in the next two days and Washington may get 8 inches, the National Weather Service said. An inch of ice was possible in parts of Georgia and South Carolina. Winter storm alerts stretch from Louisiana to Maine

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