More rain fell Monday on parts of Southern California after causing mudflows over the weekend, helping firefighters but boosting the risk of toxic ash runoff in areas scorched by Los Angeles-area wildfires. Flood watches were in effect for burn areas from recent fires that broke out around the Pacific Palisades neighborhood in Los Angeles, Altadena and Castaic Lake, said Joe Sirard, a meteorologist for the National Weather Service in Oxnard. “What that means is we have a fairly high danger of mud and debris flows once we get above those thresholds.”