An approaching winter storm is poised to open an "atmospheric river" of subtropical rain clouds on Southern California this week, but the San Diego area is expected to see just a fraction of that moisture, forecasters said Sunday.
The exact timing of the storm is currently unknown, but the heaviest rainfall is expected for Wednesday or Thursday, according to the National Weather Service.
Forecasters predicted about half an inch of rain for most of urban San Diego County and about an inch for mountain areas — though some isolated peaks could see more.
Far higher amounts of rain were forecast for the Los Angeles and San Bernardino counties, and the Santa Barbara coast, however.
For the Los Angeles area, early rainfall estimates for Tuesday, Wednesday and Thursday call for 1-1/2 to 4 inches of rain for coastal areas and 3-6 inches in the foothills and mountains. Of particular concern is that rainfall rates may hit one inch per hour in some areas, and the storm could turn scars from recent wildfires into rivers of mud.
"During the heaviest rains, it will be possible to see three-hour rainfall (of) up to 1 to 2 inches in some areas," the NWS warned. "This storm will bring the potential for major mud and debris flows on the recent burn areas, including the Thomas, Whittier, La Tuna and Creek burn areas.
"Widespread urban and small stream flooding, and rockslides, are likely at times during this event."
The storm will move east sometime late Thursday or Friday, the rain will stop and skies will clear, the NWS predicted.
