Rainfall forecast for Southern California could bring mudslide risk amid fires
Rain and cooler temperatures will bring relief to Southern California this weekend after a long period of dry, breezy weather that allowed wildfires to thrive.
The BBQ landscape between Los Angeles and San Diego hasn’t seen any significant precipitation so far, providing plenty of dry vegetation to fuel the fires. A storm system is forecast to move through the area Saturday into Monday.
But rain could be possible – up to half an inch per hour, National Weather Service meteorologist Brian Hurley said. That could trigger the fire in mountainous areas scarred by the Eaton and Hughes fires, as well as areas burned by smaller blazes over the past two weeks.
Winds remained quite strong Thursday, requiring another round of red flag warnings. However, on Friday, the warm, dry pattern and Santa Ana winds will begin to change, with coastal sea breezes pushing moist, cool air away from the ocean. The storm could hit Saturday afternoon in Los Angeles and Ventura counties, where fires are still burning.
The best chance of rain will come on Sunday, with light lingering on Monday. Brian Lewis, a weather service forecaster in Oxnard, Calif., said parts of Los Angeles, including downtown, could receive up to an inch of rain.
“Unless thunderstorms sweep through this area, we are not expecting high rainfall rates,” he said, adding there was a 10 to 20 percent chance of isolated thunderstorms.
There is also a chance of snowfall at elevations as low as 3,500 feet. The lower portions of the San Gabriel and San Bernardino Mountains could see the most snow. Altitudes above 5,000 feet may see 6 to 12 inches, with peaks as high as two feet.
Although the risk of mudslides is relatively low, officials are deploying crews to the area this week to remove debris and deploy sandbags. Los Angeles County Public Works Director Mark Pestrella said at a news conference that people who live on or near hot hillsides should be cautious, especially if their homes are not inspected after fires.
“Your best bet is to not be home when it rains,” he said.
Muds flow or debris flow – Jason Kean, research hydrologist, U.S. Geological Survey. That kind of hot water can seize the landscape, releasing a patch of trees, rocks, brush and anything else.
Residents can use burn maps created by the USGS to determine if their homes are at risk. The Eaton Fire near Pasadena is probably the most prone to mudslides. Maps show that peak rainfall, defined as more than 1.5 inches per hour falling within a 15-minute interval, will almost certainly trigger a debris flow.
The San Diego area will see the effects of the storm about 12 hours after Los Angeles as rain chances and frigid air move south Sunday and Monday.
Although expected precipitation totals for the region rose slightly on Thursday, Mr. Hurley’s weather service said California residents should not worry about major flooding. “This is a dry storm and what atmospheric rivers are going to bring is that,” he said.
