The forecast also calls for the possibility of flooding, mudflows and gusty winds.
"With all this much-needed rain, we need to be cautious and look out for the potential for flash flooding and debris flows in the forest and especially in the #BobcatFire burn area," according to the Angeles National Forest's Twitter account. "Be prepared!"
An evacuation order was issued for parts of the Alisal Fire burn scar due to the incoming storm's potential to produce a debris flow, Santa Barbara County's Office of Emergency Management said.
Thunderstorms are not expected during the storm, which is expected to move to the east by late Monday night.
13,400-acre Alisal Fire prompts evacuations in Santa Barbara County, partial closure of 101 Freeway
The main front of the storm system -- and the heaviest rain - will likely hit the Los Angeles area around noon Monday and move out of the area fairly quickly in the afternoon, the weather service said.
In the L.A. area, the forecast calls for a 40% chance of rain after midnight Sunday, increasing to a 70% chance by Monday afternoon, diminishing to 30% Monday night and becoming partly cloudy after midnight.
Upslope areas of southern Santa Barbara and Ventura counties could see 1.5 to 2 inches of rain, while other areas could get as little as a half-inch to an inch, forecasters said.
Dry and warmer conditions are expected during the rest of next week.