A storm expected to produce heavy rainfall starting Thursday evening could trigger mudslides and debris flows down slopes previously denuded by wildfires and create highly hazardous travel conditions in the San Gabriel Mountains, forecasters said.
“A storm system is expected to bring rain to the area Thursday through Saturday. The heaviest rain is expected to occur Thursday night through Friday morning when rainfall rates could reach a half-inch per hour, meeting the very low end of the USGS (U.S. Geological Survey) criteria for mud and debris flows over the Whittier, Thomas, Creek, and La Tuna burn areas,” according to a National Weather Service statement.
A flash flood watch will be in force from late Thursday evening through Friday afternoon in the San Gabriel Mountains and the San Fernando Valley.
“Rainfall of this intensity can produce dangerous mud and debris lows near the Creek and La Tuna burn areas,” the NWS warned.
“After the main front goes through Friday morning, showers are expected to continue off and on through Saturday, though intensities during this time are expected to be less than a quarter-inch per hour and not pose any risk to burn areas.”
Burbank city officials were distributing sandbags Wednesday to residents hoping to protect their properties from flooding or mud flows from the La Tuna fire burn area. Several vehicles and homes were damaged in a January mudslide on Country Club Drive.
The Los Angeles Fire Department was offering ready-to-fill sandbags at all of its stations and sand is available at select locations. More information is available at lafd.org/news. But no special parking restrictions were in effect in Los Angeles Thursday.
The storm will have the potential to generate heavy snow and strong, gusty winds in the San Gabriel Mountains in Los Angeles and Ventura counties from Thursday afternoon through Saturday morning, according to an NWS statement. Most of the heavy snow should fall Thursday evening into Friday morning, “although light snow should linger into Saturday morning as well,” it said.
South-to-southwest winds will be strongest Thursday evening through Friday night, with gusts of up 50 miles per hour possible.
“The snow and gusty winds could create very hazardous wintry driving conditions with icy roads and reduced visibility in snow and blowing snow,” warned the statement.
A winter storm warning issued by the National Weather Service and denoting highly challenging travel conditions will be in force in the San Gabriels in L.A. and Ventura counties from 7 p.m. Thursday evening through 4 p.m. Saturday afternoon. During that time, snow accumulation of up to a foot is possible above 7,000 feet and up to 18 inches at higher elevations, with between four to eight inches expected as low as 6,000 feet, the NWS said. Lighter amounts can be expected as low as 5,000 feet by Friday night.
Gusty south-to-southwest winds of between 25 and 35 mph will blow across the mountains from Thursday evening through Friday evening with gusts of up to 50 miles per hour.
“Plan on difficult travel conditions. Be prepared for reduced visibilities at times in snow and blowing snow. High profile vehicles could be impacted by the strong winds,” warned an NWS statement. “The snow and gusty winds will create very hazardous driving conditions with icy roads and reduced visibility in snow and blowing snow.”
The NWS says a winter storm warning “means severe winter weather conditions will make travel very hazardous or impossible. If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency.”
The NWS forecast mostly cloudy skies in L.A. County during daytime hours Thursday and highs of 48 degrees on Mount Wilson;56 in Palmdale and Lancaster;57 in Saugus; 58 in San Gabriel and Burbank; 59 in Avalon; 60 in Long Beach and at LAX; 61 in Downtown L.A. and Pasadena; and 62 in Woodland Hills. Precipitation is forecast through Saturday.
Rain is forecast in Orange County, along with highs of 58 in San Clemente; 60 in Yorba Linda and Mission Viejo; 62 in Newport Beach, Laguna Beach, Irvine and Fullerton; And 63 in Anaheim. Showers are forecast in Orange County Friday, followed by three days of sunshine.
Rescuers have been “highly focused” as usual in their rain preparations, according to Brian Humphrey of the Los Angeles Fire Department.
“We don’t want any property damage but the greatest concern is for public safety,” he said.
Flood control channels, washes, arroyos and storm drains can become deadly when it rains and children are especially drawn to the novelty of rising and rushing water, he warned, adding that trying to rescue a person or pet is dangerous and should be left to public safety personnel.
“The outcomes historically have been terrible,” Humphrey said.
Highly trained swiftwater rescue teams will be at the ready and deployed as needed, he said.
“This is not a startling occurrence to us,” he said. “We know it rains typically at this time of year.”
Humphrey also advised the public to heed the words of lifeguards, public health officials and others when visiting area beaches, including in the days after rains have stopped, due to concerns over rough surf, bacteria and debris.
—City News Service
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