The Santa Ana winds that have fueled wildfires for weeks in Southern California finally stopped blowing on Friday, and an unusually long period of dry weather was on track to end in Los Angeles County as a cold storm approached on Saturday.
The system was expected to deliver light to moderate rain that will fall intermittently Saturday night through Monday. The weather will give the arid landscape and withered vegetation a much-needed soaking and benefit firefighting crews.
Still, the forecast showed a small risk that bursts of heavy rain could cause flash floods and mudslides around areas of Los Angeles County recently scarred by wildfires, including the northwest (Hughes fire), east (Bridge fire), southwest (Franklin and Palisades fires) and especially the central area where the Eaton fire burned.
The National Weather Service issued a flood watch for those areas from 4 p.m. Sunday to noon on Monday, when there is the highest chance for rain and risk for thunderstorms.
Kristan Lund, a meteorologist with the Weather Service, called flooding the worst-case scenario for the conditions in Los Angeles, where there is up to a 20 percent chance that debris flows could damage roads and structures.
“What we’re telling people is to avoid the area during the watch period,” Ms. Lund said. “Use sandbags to protect your property, and if residents decide to stay, make sure to stock up on supplies in case road access is blocked.”
The Los Angeles area has seen its driest start to the rainy season on record and has not measured significant rainfall since last spring. Since May 1, the Weather Service’s gauge in downtown Los Angeles has measured just a little more than a quarter-inch of rain. This weekend’s expected storm has the potential to bring nearly four times that amount.
The burn scars in Los Angeles County, where trees and brush were devoured by flames, are most likely to benefit from the rain. “If we get gentle rains, it’s going to help make those burn areas recover and re-vegetate,” said Jayme Laber, a hydrologist with the Weather Service.
By midafternoon on Saturday, rain had yet to arrive in Los Angeles County, but the first drops were expected to fall by the evening, with showers increasing Sunday into Monday. Most locations across the county, including downtown Los Angeles, are expected to record up to an inch of rain in the storm.
But isolated showers and thunderstorms could bring rain that falls at three quarters of an inch an hour, and the heavier rains could lead to debris flows Sunday afternoon through Monday afternoon. The thunderstorms could also kick up strong, damaging winds, drop small hail and cause water spouts over the ocean, the Weather Service said.
The weather is expected to temporarily lower the risk of wildfires, but this one storm won’t fully end it.
“It’s only going to help things out for a couple weeks,” Matt Shameson, a meteorologist with the U.S. Forest Service, said of the storm. “If we get another one or two decent systems, that will help us out significantly.”
The good news is that another set of showers could come over the region sometime next week, Mr. Shameson said.
