Flooded roadway in Los Angeles
Flooding on a Los Angeles-area roadway. File photo courtesy OnScene.TV

The last and strongest of three storms to hit Southern California this week slid into the region Thursday, generating periods of heavy rain, which could trigger street flooding and shallow mud and debris flows in several areas previously denuded by wildfires, National Weather Service forecasters said.

The rain could unleash mudslides and debris flows “in and near recent burn scars across Los Angeles, Ventura, and Santa Barbara Counties. These include the Hill, Sherpa, South, Stone, Thomas, Whittier and Woolsey burn scars,” according to an NWS statement.

The weather service at 5:40 a.m issued a flood advisory for most of L.A County and eastern Ventura County and said it would expire at 8:30 a.m. This was in response to Doppler radar and rain gauge indications that widespread moderate rain was falling, “with numerous embedded heavy showers.”

Rainfall rates were highly variable but generally averaged .15 to .30 inches per hour, with up to .50 inch per hour in some areas.

“The rain will cause widespread ponding of water on area roadways through the morning commute with flooding of low lying areas,” warned an NWS statement.

Also in L.A. County, a flash flood watch will be in force until 1 p.m. along the coast, in the Santa Monica Mountains Recreational Area, the San Gabriel Mountains, the San Fernando and Santa Clarita valleys, beach cities, Long Beach, Beverly Hills and Hollywood. In all, it covers the Woolsey, Hill, South, and Stone burn scars in Los Angeles and eastern Ventura Counties, the NWS said. Forecasters say they expect peak rainfall rates of between a half-inch and three quarters of an inch of rain per hour in the watch zone.

“Rainfall of this intensity can produce shallow mud and debris flows in and near recent burn areas. In addition, localized flooding is possible across other parts of Los Angeles and Ventura Counties, along with rockslides and mudslides that could produce road closures,” according to the NWS statement.

“A flash flood watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation,” said the NWS, adding that Southern California residents in or below the recently burned areas are urged to take the steps necessary to protect their property. Persons in the watch area should remain alert and follow directions of emergency preparedness officials.”

A rockslide prompted the closure of Topanga Canyon Boulevard between Pacific Coast Highway and Grand View Drive, according to the Los Angeles County Sheriff’s Department. Other closures include Malibu Canyon Road between Piuma and Mailbu Knolls and Decker Road between Mulholland Highway and PCH. A portion of La Tuna Canyon in Sun Valley was closed because of a rock slide Wednesday night, but has since reopened.

A tree fell along Lookout Mountain Avenue in the Hollywood Hills, knocking out power to 300 customers, according to a Los Angeles Department of Water and Power outage map. Repair crews were working to clear the tree and restore power.

Along the coast, an extended period of high surf is expected through Friday, the NWS said. A high surf advisory will be in effect in L.A. County until 2 p.m. Thursday, followed by a less serious high surf warning from 2 p.m. Thursday until 9 p.m. Friday.

Breaking waves of 5-8 feet will pound the shore through Thursday morning, then increase to 6-10 feet, then 10-15 feet Friday morning, according to an NWS statement.

“Minor coastal flooding is possible Thursday, with moderate coastal flooding and significant beach erosion likely on Friday, it said.

Amid the high surf, ” there is an increased risk for ocean drowning. Rip currents can pull swimmers and surfers out to sea. Large breaking waves can cause injury, wash people off beaches and rocks and capsize small boats near shore,” warned an NWS statement. Moderate coastal flooding is possible over low-lying coastal areas including beaches, beach parking lots and harbor walkways, and with vulnerable coastal roadways during the highest surf and tides.”

Off the coast, a gale warning expired at 3 a.m. Thursday, and a small craft advisory will follow suit at 9 a.m.

In the San Gabriel Mountains and the Antelope Valley, a wind advisory will be in effect until 3 p.m. Winds of 20-35 mph are expected, along with gusts of up to 55 mph.

“Gusty winds will make driving difficult, especially for high-profile vehicles,” warned the NWS, saying that driving will be particularly difficult on Interstate 5 and Highways 14 and 138, especially for high profile vehicles.

The NWS forecast rain in L-A County Thursday and highs of 52 degrees on Mount Wilson; 57 in Palmdale and Lancaster; 59 in Saugus; 60 in Avalon … Pasadena … San Gabriel; 61 in Burbank; 62 in Downtown L.A. … Long Beach … Woodland Hills and at LAX. A mix of partly cloudy and sunny days are forecast over the next six days.

In Orange County , showers were forecast Thursday, along with highs of 48 on Santiago Peak; 55 on Ortega Highway at 2,600 feet; 58 in Fremont Canyon; 60 in Yorba Linda; 61 in Laguna Beach and San Clemente; 62 in Anaheim and Mission Viejo; and 63 in Newport Beach, Fullerton and Irvine. Orange County will also experience a mix of partly cloudy and sunny skies over the next six days.

Leave a comment

Your email address will not be published.