MONTPELIER (AP) - Icy conditions in Vermont have police urging residents to avoid unnecessary travel as a winter storm is expected to bring snow, sleet and freezing rain to northern New England.

The National Weather Service says a half-inch or more of ice could accumulate in some areas, making travel hazardous and potentially causing widespread power outages. The greatest potential for heavy precipitation is Saturday night through Sunday.

A winter storm watch is in effect for northern Vermont, northern New Hampshire and western Maine through much of the weekend. An ice storm warning is in effect for two counties in far northern New York through late Sunday.

Problems began Friday evening in Vermont. State police reported numerous issues on Interstate 89, including tractor trailers blocking the roadway after skidding on the slippery roadway.