Officials in California are bracing for what could be the biggest rain storm of the winter season, alerting residents to avoid travel during the expected torrential downpours and warning about the potential for flooding and mudslides, especially in fire-ravaged areas.

An atmospheric river, the second to wallop the state in recent weeks, will bring 2 to 4 inches of rain to much of the California coast, with over 8 inches possible in some isolated areas, according to AccuWeather. The rain is expected to begin Wednesday night and move into Southern California on Thursday, when the heaviest downpours are forecast.

“The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and burn scars the most vulnerable,” the national weather service said. “The risk of flash flooding will be highest in and near recent burn scar areas in Southern California.”

The weather service office in Los Angeles said heavy rain over charred land “could trigger life-threatening and damaging flooding and debris flows.”

Ahead of the rain, Los Angeles Mayor Karen Bass announced several measures to mitigate the potential for mudslides in Pacific Palisades, an affluent neighborhood tucked between the San Gabriel Mountains and the Pacific Ocean that was ravaged last month by one of the most destructive wildfires in the state’s history.

Bass said “erosion control measures” include more than 7,500 feet of concrete barriers and thousands of sandbags. Additionally, the city has hastened the removal of fire debris and cleared storm drains, she said.

“The city is making preparations to keep Angelenos safe and to prevent additional damage to burn areas that could delay rebuilding,” Bass said in a post on the social media platform X.

Flash flood watches from San Francisco to San Diego were set to go into effect beginning Thursday.

In addition to the rain, the system will bring several feet of snow and high winds to the Sierra Nevada Mountains, triggering winter storm warnings describing “difficult to impossible” travel conditions on mountain passes.