Rain was falling in Sacramento and snow was causing travel troubles in the Sierra Nevada on Friday as a fairly cold winter storm swept into Northern California. By Christmas Eve, snowfall will become insignificant in the mountains, according to the National Weather Service. And in Sacramento, the rain will clear the night before Christmas. But before then, travel to the high country will be challenging with car chains most likely to be as common as ugly Christmas sweaters. The snow level is expected to be around 4,000 feet during the daylight hours, dropping to 2,500 feet Friday night.