(CNN) -- A strengthening El Nino is expected to bring torrential rain Thursday to parts of Southern California, including Los Angeles, and authorities warned of possibly severe mudslides in areas denuded by forest fires.
The storm could dump 8 inches to 10 inches of rain on the Los Angeles area and higher amounts in the foothills, the National Weather Service said.
Late Tuesday, Los Angeles Mayor Antonio Villaraigosa -- expecting a dangerous storm Wednesday -- urged hundreds of Californians to leave their homes. A torrential rainfall Tuesday unleashed flooding and spawned a rare tornado warning.
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There has been some resistance to the advice, a detective with the Los Angeles Police Department said. The detective, who wouldn't give her entire name, said she didn't know how many people decided to leave.
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There was heavy rain Wednesday in San Francisco and Sacramento, California, but Los Angeles had little precipitation as of about noon.
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A warm ocean current from the South Pacific is responsible for this week's storms, said CNN meteorologist Chad Myers.
With little vegetation to help contain the water, the vast expanses in southern California that were hit by wildfires late last summer are causing concern for officials. The largest of the fires -- known as the Station Fire -- charred 250 square miles of land last summer north and east of Los Angeles.
"If you are lower in elevation than where a fire happened earlier this year, you need to be very, very cautious," Myers said.
Forecasters said several feet of snow would fall in the higher elevations of the Sierra Nevada through the rest of this week, as low pressure systems continue moving into the area.