Rain is finally coming to Southern California: What you need to know
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- Weekend storm is expected to bring some relief.
- But fire weather could return if dry weather and Santa Ana winds return.
- Risk of landslides in burned areas is low, but still exists, forecasters say.
After an epic dry streak that helped fuel devastating fires, Southern California this weekend will get its first real rain of the winter.
Any moisture will help with the region’s parched, combustible landscape. Yet there is concern that the upcoming rain may provide only temporary relief. After this weekend, a dry spell could return — raising serious questions about whether dangerous fire weather could return sooner than later.
One big problem: The Santa Ana wind season can persist through February and March, and one weekend of modest rainfall would be no match for more weeks of dry winds and weather, should that materialize.
“We have not been in this territory before for dryness, not this deep into a winter — ever,” said Alex Tardy, a meteorologist with the National Weather Service office in San Diego, which also provides forecasts for Orange County and the Inland Empire. “This has really been extreme for Southern California.”
The rains are also bringing anxiety about potential for debris flows in areas recently besieged by fire in Los Angeles County, with the Palisades and Eaton burn scars being of most concern, forecasters say.
Most likely, the storm won’t amount to more than a light rain, spread out over many hours. But forecasters are anticipating isolated areas that could see rainfall rates of half an inch to three-quarters of an inch per hour, said Ryan Kittell, a meteorologist with the weather service’s Oxnard office. Those are rates that have the potential of producing debris flow if they emerge over recently burned areas.
The period of most concern, which could bring the highest intensity of rainfall over this storm system, is from Sunday at 4 p.m. to Monday at noon.
This article is provided free of charge to help keep our community safe and supported during these devastating fires.
Southern California is in the throes of a historically dry start to winter — shattering records that have been collected since the late 19th century. And the region is rapidly running out of time to catch up on the severe deficit in rainfall before the winter rainy season ends.
The Southland has been stuck in a punishing weather pattern since October, where not a single significant storm has passed over the region. In January, the weather pattern worsened — with the storm track blocked from “not just Southern California, but all of the West — from Seattle southward,” Tardy said.
Coverage of the Hughes, Sepulveda and Laguna fires in Southern California during a fourth consecutive day of red flag fire weather warnings.
The lack of rain came as seven separate Santa Ana wind events hit Southern California in January alone, Tardy said, a dangerous combination in creating fire weather conditions as the air and vegetation dry out, making brush especially flammable. There have been 15 Santa Ana events since November, Tardy said.
“The Santa Ana winds have really taken their toll on sucking the moisture out of the atmosphere,” Tardy said. “There’s no marine layer, because it’s been blown out the sea. The desert has come to the coast.”
Concern about a dry start to February
After this weekend’s rains, the long-term outlook suggests that Southern California is most likely going back to a dry pattern, Tardy said.
It’s the driest start to the water year, which began Oct. 1, on record in places such as San Diego, Orange County, the Inland Empire, as well as Los Angeles International Airport, UCLA, Van Nuys, Woodland Hills and Camarillo.
Coverage of the Hughes, Sepulveda and Laguna fires in Southern California during a fourth consecutive day of red flag fire weather warnings.
For other spots, it’s the second-driest start to the water year, which includes places such as downtown Los Angeles, which has received just 0.16 of an inch of rain since Oct. 1. That’s only 2.5% of what downtown L.A. gets on average by this point in the season — 6.38 inches of rain. The annual average rainfall for downtown is 14.25 inches.
First real rain of winter expected
This weekend’s rains are mostly expected to bring a welcome respite after several weeks of almost unrelenting fire weather. There have been red flag warnings in some parts of Southern California for 15 of the last 18 days.
This week brought a number of new threatening wildfires to Southern California, including the Hughes fire, which has burned more than 10,300 acres since Wednesday around Castaic Lake, just north of Santa Clarita. By Friday, the Hughes fire was 56% contained. The 23,400-acre Palisades fire was 77% contained, and the 14,000-acre Eaton fire was 95% contained.
Fire crews on Friday were still battling the Border 2 fire, which broke out Thursday afternoon in the Otay Mountain wilderness in San Diego County. The blaze has charred more than 5,300 acres and was 10% contained on Friday and had triggered evacuations.
The rains are expected to break a record streak of minimal rainfall for downtown Los Angeles, which has not seen more than one-tenth of an inch of rain on a calendar day since 0.13 of an inch of rain fell on May 5. As of Friday, it has been 264 days since downtown L.A. has received one-tenth of an inch of rain or more. That’s a record for downtown — the previous mark was 253 consecutive days, from Feb. 25, 2008, to Nov. 3, 2008.
Forecasters are predicting widespread rain over the weekend, beginning with showers Saturday night or early Sunday morning in Los Angeles County, according to the National Weather Service. On Friday afternoon, the weather service said rainfall amounts could be higher than forecasters initially expected. Los Angeles and Ventura counties could see half an inch to an inch of rain, and up to 2 inches in the mountains, said Kittell.
Residents in Pacific Palisades, Altadena and Rancho Palos Verdes fear too much rain too fast will cause landslides and create, as one said, a ‘soupy mess.’
San Diego, Anaheim, Irvine, San Clemente, Riverside and Lake Elsinore could get 0.7 to 1 inch of rain. San Bernardino, Ontario, Temecula, Oceanside, Escondido and Mira Mesa could get 1 to 1½ inches of rain.
The increased rainfall forecast is a result of the low-pressure system, dropping in from Canada, appearing to veer a little bit more to the west — slightly more off the coast of Southern California — than initially expected, which would make this storm wetter.
Periods of rain could start as early as Saturday morning and last through Monday night. But the highest chance for rain will be Saturday night into Sunday, Kittell said of Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties.
The heaviest potential for rainfall will be Sunday and Monday for San Diego, Orange, Riverside and San Bernardino counties.
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Risk of thunderstorms and landslides
There is a 15% to 25% chance of thunderstorms across the region, which could happen at any time, and could bring isolated, brief heavy rainfall at rates of half an inch an hour, Kittell said.
There is a 10% to 20% chance of significant debris flow for recently burned areas of L.A. County, up from an earlier estimate of 5% to 10%.
A flood watch will be in effect between 4 p.m. Sunday through 4 p.m. Monday for recently burned areas, including the Eaton, Palisades, Franklin, Hughes and Bridge fires. The flood watch will not cover the Mountain fire burn scar in Ventura County.
Of the burn scars, the Eaton and Palisades burn zones are of the most concern for debris flows — a type of damaging landslide that involves water rapidly flowing downhill, picking up mud, rocks, branches and sometimes massive boulders.
“The most likely outcome is that there might be some shallow debris flows that are kind of minor impacts, but there’s enough of a threat that we definitely at least want to highlight that,” Kittell said.
Hillsides are vulnerable to landslides after wildfires because the fires make the soils repellent to water, and instead of being absorbed, rain flows downhill and picks up rocks and debris.
Debris flows can be deadly. In January 2018, 23 people died and at least 130 homes were destroyed when a river of mud and rock flowed through coastal Montecito, which had been burned less than a month earlier in the Thomas fire.
Los Angeles city and county officials started preparing for the rain this week. Public works said it would be installing barriers, removing debris and diverting runoff from the stormwater system into the sewer system, where it can be treated, ahead of the wet weather. Crews are also clearing drains and roadways, placing sandbags to shore up vulnerable infrastructure and preparing debris basins for the incoming storm, officials said.
Coverage of the Hughes, Sepulveda and Laguna fires in Southern California during a fourth consecutive day of red flag fire weather warnings.
There is also a moderate risk of small hail.
Snow levels could fall to an elevation of 3,500 feet above sea level. There could be 6 to 12 inches of snow in the San Gabriel Mountains. There’s a potential for perhaps 1 to 2 inches of snow on the Grapevine section of Interstate 5, which could result in delays on the freeway, Kittell said.
Wrightwood and Big Bear Lake could get 8 inches to 12 inches of snow. That raises the prospect of authorities requiring motorists to install chains on tires when driving to mountain areas like Big Bear.
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