Torrential rains unleashed widespread flash flooding and mud flows across Southern California, as authorities warned motorists to stay off roads while urging residents in flood zones to evacuate or shelter in place over the Christmas holiday. In the rain-soaked mountain resort of Wrightwood, east of Los Angeles, emergency crews answered dozens of rescue calls and pulled drivers to safety from submerged vehicles, officials said. A rare tornado warning was even issued in east-central Los Angeles C