Much-needed rain eyes Southern California this weekend: What it means for burn scars, wildfires

LOS ANGELES – After months of dry, windy conditions contributing to deadly wildfires in Southern California, the parched region is finally set to receive much-needed rain this weekend, which is good news for firefighting but presents a new danger of flash flooding and mudslides.

A significant change in the weather pattern is coming as an area of low pressure moves south across the region. According to the FOX Forecast Center, it's still too early to tell just how much rain will fall, but confidence is increasing about the chances of rain beginning Saturday.

The forecast for the next 10 days shows rain falling in Ventura and Los Angeles counties, ranging from a half-inch to upwards of 2 inches. 

Higher elevations between 3,000 and 4,000 feet are likely to see snow with much colder temperatures in the mountains. 

Still, the needed moisture will bring new threats to burn-scar areas with ash and fire debris. These incredibly parched areas can flood quickly without vegetation to absorb the water. 

"Just a short period of moderate rainfall on a burn scar can lead to flash floods and debris flows," the National Weather Service said. "Rainfall that is normally absorbed by vegetation can run off almost instantly. This causes creeks and drainage areas to flood much sooner during a storm, and with more water, than normal."

In addition, soils inside burn scars can contain significant amounts of mud, boulders, vegetation and ash containing toxic materials.

Debris slides can also be triggered without rain. FOX 11 Los Angeles reports a home spared by the Palisades Fire was cut in half by a debris slide last week.

Resources are being deployed across Los Angeles County ahead of the incoming rain.

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"Our objective in this incident is to protect the public property and the natural environment from potential mud and debris flows and pollution," L.A. County Department of Public Works Director Mark Pestrella said on Wednesday. "Currently, our crews are clearing debris from streets cleaning and preparing debris basins, deploying sandbags and other systems to keep runoff with ash and other burnt debris from entering the storm drain system."

Residents can request county engineers to assess their properties for potential risks caused by the fires and debris flow mitigation. 

Pestrella advised residents with homes located along the burn area with a slope behind their property above 20 feet to leave. 

"Your best bet is not to be in that home when it rains. The most conservative thing to do is to not be in that home when it rains," he said.

Pestrella said residents who have returned home after the Palisades and Eaton fires are being asked to stay off the roads while crews work to prepare the area ahead of the rain and clear debris afterwards.

"We do expect sediment and debris to make its way to the street systems in the Palisades area, in the Eaton area," he said. "This is not it's not expected to be a tremendous amount of debris, but enough to actually cause transportation problems for our first responders as well as residents that may be trying to travel."

However, before the rain arrives, Southern California remains under a Fire Weather Warning through Thursday due to renewed Santa Ana winds.