A fierce winter storm that pummeled the upper Midwest coated the Northeast with ice as freezing rain closed Kennedy International Airport for about an hour, knocked out power and sent motorists sliding. The storm headed into Quebec, and cold air rushed in behind it, threatening to drop wind-chill readings 40 to 50 degrees below zero in New York and New England early today, the National Weather Service said. Accidents on icy roads killed four people in New Jersey, two in Iowa and one in Michigan. A 25-vehicle pileup in Brooklyn, N.Y., left at least 10 people with minor injuries. The weather service had its first severe weather report of the year--a thunderstorm at Buffalo, N.Y., with 62-m.p.h. winds and sleet.