After a lackluster start to the rainy season in Southern California, the region is expected to see a surge of moisture this week that forecasters say could be the beginning of a soggy March.
A warm front arrived across the Central Coast late Tuesday and will spread south into Los Angeles through the day Wednesday, bringing with it a sprinkling of moisture ahead of the brunt of the storm. The bulk of the rain is expected to arrive late Wednesday and last through early Friday in Los Angeles County, said Robbie Munroe, a meteorologist with the National Weather Service in Oxnard.
Next week is expected to deliver even more rain to Southern California’s parched landscape. The region endured one of its driest starts to the rainy season in recorded history, which helped fuel one of the most destructive fire seasons ever.
As of Tuesday, downtown L.A. had received 5.58 inches of rain since the water year began Oct. 1. That is below the average for this point in the water season, 11.08 inches. The annual average is 14.25 inches.
“We’ve been playing catch-up, it feels like, the whole winter after an extremely dry period through January,” Munroe said. “February was still a little below normal, but at least it kind of got us closer to what we might see this time of year.”
Between a tenth of an inch and an inch of rain is expected for the coastal regions during this week’s storm. South-facing mountain slopes could see 1 to 2 inches of rain. Two to 5 inches of snow could fall in elevations above 4,500 feet, according to the weather service.
The storm is also expected to unleash strong winds. Gusts could peak between 30 and 50 mph Thursday.
The weather system also brings the potential for thunderstorms, particularly late Wednesday through Thursday, which could deliver heavy downpours along with gusty winds, lightning, small hail and even weak tornadoes.
Although forecasters expect the moisture will be mostly beneficial, too much rain too quickly could result in debris flows and damage for the Palisades and the Eaton fire burn scars.
“We’re not going to get continuous rain. It’ll come in episodes, and there could be a lot of dryness between those episodes,” said Ariel Cohen, the meteorologist in charge at the National Weather Service in Oxnard. “Don’t let your guard down after the first round of rain comes. It might be coming back really soon.”
Peak rainfall rates could reach between a tenth of an inch and a third of an inch per hour, with rain rates in some areas reaching half an inch per hour. Experts say the risk of mud and debris sliding off burned hillsides rises once rain starts falling at a rate of half an inch per hour.
There’s a 10% to 20% chance of significant flooding and debris flows in the Los Angeles County burn areas, according to the weather service.
“There’s no guarantee at all, but the possibility does exist,” Cohen said of dangers in the burn areas. “It’s something to really keep an eye on because our confidence in those significant debris flows occurring may not be particularly high until right before they occur.”
The burn zones have already seen the effects of wet weather this winter.
However, this week’s storm is not forecast to be as strong.
The system is also expected to bring fresh powder to California’s mountain ranges.
In Northern California, the weather service issued a winter weather advisory for the Lake Tahoe area warning of snow accumulations of 2 to 6 inches at elevations below 7,000 feet and 6 to 12 inches at higher elevations between 4 a.m. Wednesday and 10 p.m. Thursday. Winds are expected to gust as high as 55 mph over the highest peaks.
In Southern California, the weather service issued a winter weather advisory for Los Angeles, Santa Barbara and Ventura counties’ mountain ranges. The warning, which will last from 7 p.m. Wednesday to 7 a.m. Friday, says snow accumulations could be 3 to 6 inches for elevations above 6,000 feet, except locally up to 10 inches near Wrightwood.
Elevations of 4,000 to 6,000 feet could see a dusting of up to 3 inches, according to the weather service.
The coming storms could help bolster the state’s snowpack, which has suffered during the warm, dry winter. As of Tuesday, the snowpack — which typically melts to supply nearly a third of the state’s water — was 83% of average for this time of the year.
A wet March could also help the region delay its return to high fire season, Munroe said.
“The longer we can have wet weather into the spring, it will usually help us delay when things get a chance to really dry out,” Munroe said.
After Friday, the region could see a few days of dry weather before more rain returns Sunday night. That system could bring light to moderate rain through Tuesday. Another storm forecast to arrive the day after that and last through March 13 could potentially bring bands of heavier rain, but exact amounts aren’t yet certain.
