The last and strongest of three storms to hit Southern California pounded the region Thursday, generating periods of heavy rain amid fears of street flooding and shallow mud and debris flows in several areas previously denuded by wildfires.
The National Weather Service issued a flood advisory Thursday morning for most of L.A County, and although the warning expired before noon, several streets and even some freeway sections around the Southland were closed due to flooding or mudslides.
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 rates later increased to between a quarter-inch and a half-inch per hour, according to the NWS.
“With these rainfall rates, flooding of roadways and low-lying areas will continue. Additionally, there may be some minor mudslides and rockslides in and around the recent burn areas,” according to an NWS statement.
“Turn around, don’t drown when encountering flooded roads,’ urged the statement. “Most flood deaths occur in vehicles.”
“The rain will cause widespread ponding of water on area roadways through the morning commute with flooding of low lying areas,” warned the NWS.
In Malibu, both directions of Malibu Canyon Road were shut down between Mulholland Highway and Civic Center Way due to rock slides. All lanes of Highway 27 were closed between Pacific Coast Highway and Fernwood Pacific Drive because of mud on the roadway.
In Boyle Heights, flooding in the tunnel closed the northbound 101 Freeway at the I-10/Seventh Street interchange, and traffic was being diverted onto the eastbound 10 Freeway.
A portion of La Tuna Canyon in Sun Valley was closed because of a rock slide Wednesday night, but has since reopened.
In the Hollywood Hills, 21 homes were evacuated as a precaution after soil movement was detected near a home under construction in the 1800 block of North Stanley Avenue.
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 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.
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.”
The Los Angeles County Health Officer is urging swimmers and surfers to steer clear of water near storm drains for a few days, which are flushed out by rain and can contain hazards that can make them ill.
The beach water use advisory was in effect until at least 7 a.m. Monday.
“Avoid swimming, surfing and playing in ocean waters around discharging storm drains, creeks and rivers,” Dr. Muntu Davis said. “Bacteria, chemicals, debris, trash and other public health hazards from city streets and mountain areas are likely to contaminate ocean waters in and around these outlets after a rainfall.”
For updated beach conditions, call the county’s 24-hour hotline at (800) 525-5662 or visit publichealth.lacounty.gov/beach/.
In the San Gabriel Mountains and the Antelope Valley, a wind advisory will be in effect until 3 p.m. Thursday. 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.