As traffic creeps along Route 15 north of Frederick, Md., on Sunday, Mike Goldsmith lends a hand to a motorist who had skidded off the roadway. A winter storm that glazed much of the Southeast in a thick coat of ice moved up the coast Sunday, dropping snow, sleet and rain from the Carolinas to southeastern New York. By Sunday evening, 6 inches of snow had fallen in western Maryland. In Virginia, more than 150,000 customers lost power as conditions worsened through the day. The storm was to hit New England today.