A winter storm warning has been issued for the Northern Sierra and western Plumas County from 9 a.m. Sunday until 4 a.m. Monday. The heaviest snow is expected Sunday afternoon and evening. Weekend travel is encouraged before Sunday morning if possible. Snow levels will start at pass levels and drop to between 4,000 and 5,000 feet Sunday night. Winds are expected up to 30 mph further impairing driving conditions. The storm is expected to wind down Monday. Total snow accumulations of 1 to 2 feet are expected with up to 3 feet at the higher elevations.