(Allen J. Schaben / Los Angeles Times) The Pineapple Express storm bearing down on Southern California could bring heavy rain and strong winds throughout Christmas week, potentially triggering mudslides, downing trees and flooding not only freeways but also homes and businesses. If the forecasts are right, this could be one of the stormiest Christmases in recent memory for Southern California. There's an 80% chance downtown Los Angeles will get 2 or more inches of rain from Tuesday through Christmas Day. The last time downtown got 2 or more inches of rain over Christmas Eve and Christmas Day was in 1971.