* WHAT...Heavy snow expected. Total snow accumulations between 10 and 18 inches. * WHERE...A portion of central Pennsylvania. * WHEN...From 10 PM this evening to 1 PM EST Monday. * IMPACTS...Travel will be very difficult to impossible. Widespread and prolonged travel disruptions are expected. * ADDITIONAL DETAILS...Snow will overspread the area Saturday night, becoming heavy at times through Sunday with accumulation rates of one to two inches per hour at times. Frigid temperatures and wind chills are expected before, during, and after the winter storm. Some blowing and drifting snow is possible.