By Rajesh Kumar Singh CHICAGO (Reuters) – U.S. carriers on Friday canceled thousands of flights through the weekend in anticipation of a winter storm forecast to bring high winds and heavy snow across the Northeast and Mid-Atlantic. The National Weather Service said in an advisory that the Nor’easter would result in dangerous blizzards and make travel “nearly impossible.” Flight-tracking service FlightAware reported about 4,900 U.S. flights were canceled between Friday and Sunday. Delta Air Lines said it would suspend operations at LaGuardia and John F. Kennedy airports in New York, Newark Lib…