Rain pelts L.A.; Malibu schools shut; I-5 closed at Grapevine

Los Angeles County’s first significant storm in more than eight months has already forced the closure of the 5 freeway at the Grapevine, unleashed mud on roadways, and triggered the closure of Malibu’s public schools Monday due to dangerous road conditions.

There’s still concern about the potential for mudslides and rockslides in L.A. County areas recently burned by wildfire. Before 4 a.m., a severe thunderstorm capable of producing waterspouts and hail was detected near Catalina Island.

The National Weather Service has issued a flood watch for several recently burned areas, warning of a 10% to 20% chance of significant flash flooding and debris flows capable of damaging roads and homes in and around areas devastated by wildfires.

Here’s what you need to know:

Impacts

Interstate 5 at Grapevine shut

Interstate 5 was closed at the Grapevine — the key section of roadway through the Tejon Pass that connects Los Angeles County with the Central Valley.

The Grapevine was ordered shut late Sunday night, and crews were “working to clear snow,” Caltrans said. Caltrans on Monday morning suggested using U.S. 101 as an alternate route between Los Angeles County and Central California.

“The closure will be in place for an unknown duration,” the California Highway Patrol said.

Malibu public schools shut on Monday

The Santa Monica-Malibu Unified School District announced all four of its Malibu schools are closed Monday due to dangerous road conditions and challenges accessing the schools. Public schools in Santa Monica remain open.

Pacific Coast Highway affected by flooding

Part of Pacific Coast Highway was closed due to flooding in Topanga Canyon, National Weather Service meteorologist Joe Sirard said Sunday. A rain gauge picked up 0.74 of an inch on Topanga Canyon Boulevard on the edge of the fire boundary, he said.

Mudflows forced the closure of Pacific Coast Highway west of Topanga Canyon Boulevard, Caltrans said Sunday afternoon.

Caltrans’ QuickMap website said early Monday that the northbound Pacific Coast Highway remained closed at Topanga Canyon Boulevard, and southbound PCH was closed from the Sweetwater Canyon Road.

Topanga Canyon Boulevard, also known as California 27, is closed. The rains caused Topanga Creek to overflow, and debris covered the roadway. Crews that were fixing damage from the Palisades fire had to evacuate, Caltrans said.

Vehicles trapped in mud

Four vehicles were trapped in mud along Mulholland Drive, around the 4100 block of Alhama Drive in Woodland Hills, Sunday evening.

No one needed to be rescued, the Los Angeles Fire Department said, but officials did summon tow trucks to remove the trapped vehicles.

Movement of mud and ash from burned areas

Officials at a Pacific Palisades town hall said the Los Angeles Fire Department was working to remove mud that had accumulated on Palisades Drive on Sunday evening and that black ash-laden water had reached the beach.

White-out conditions in the high desert

Caltrans said a section of eastbound California 138 — in Los Angeles County’s high desert — was experiencing white-out conditions due to heavy flurries. Caltrans said to avoid California 138 between the San Bernardino County line to the junction with California 18.

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The California Highway Patrol said snow was falling at the Cajon Pass — the mountain pass that connects the San Bernardino area to the Mojave Desert.

Caltrans plows were plowing Interstate 15, the CHP said.

“If you’re traveling, slow down, increase distance, and expect delays,” the CHP said.

Concern about mudslides in recently burned areas

Flood watch for burned areas

A flood watch is set to continue through 4 p.m. Monday for the burned areas of the Eaton fire in the Altadena and Pasadena areas; the Palisades and Franklin fires in the Pacific Palisades and Malibu areas; the Hughes fire around Lake Castaic; and the Bridge fire in the San Gabriel Mountains west and southwest of Wrightwood.

There’s a 15% to 25% chance of thunderstorms over a wide swath of Southern California through Monday afternoon, which can bring heavy rainfall, and with it, the risk of mudslides and debris flow.

A debris flow can happen when water rapidly flows downhill and, besides mud, picks up rocks, branches and sometimes boulders — something capable of damaging cars and homes. It can be life threatening.

How much rain and snow has fallen

Rainfall

Downtown L.A. has so far received 0.47 inches of rain from this storm, including 0.11 of an inch on Saturday.

Saturday’s rainfall alone breaks a record dry spell for downtown Los Angeles. The last time downtown got one-tenth of an inch of rain or more on a single calendar day was May 5, when 0.13 of an inch of rain fell.

That means, starting May 6 through Friday, downtown L.A. has spent 264 consecutive days without seeing at least one-tenth of an inch of rain on a single calendar day. The last record of this kind for downtown was 253 consecutive days, from Feb. 25, 2008, to Nov. 3, 2008.

Here’s how much rain has fallen in this rain storm, through 10 p.m. Sunday:

Fillmore: 1.36 inches
Pepperdine University: 1.15 inches
Thousand Oaks: 1.13 inches
Calabasas: 1.06 inches
Ventura: 1.02 inches
Santa Monica Pier: 0.98 inches
Northridge: 0.97 inches
Bel-Air: 0.93 inches
Canoga Park: 0.9 inches
Beverly Hills: 0.83 inches
Claremont: 0.56 inches
La Cañada Flintridge: 0.53 inches
Downtown Los Angeles: 0.47 inches
Whittier: 0.45 inches
Alhambra: 0.4 inches
Culver City: 0.2 inches

Snowfall

Heavy snow was expected in the eastern San Gabriel Mountains, with total snow accumulations of up to 14 inches, the weather service said. Snow levels could drop to 3,000 feet above sea level into Monday.

Travel in and around Mount Baldy, Wrightwood, Mount Wilson and along the Angeles Crest Highway “could be very difficult to impossible,” the weather service said Monday morning.

Where L.A. stands in terms of its seasonal rainfall

Downtown L.A. has now seen 0.63 of an inch of rain since Oct. 1. That’s a drop in the metaphorical bucket of how much downtown on average gets at this point in the season — 6.66 inches. That’s about 9% of the average.

Before this weekend’s rain, the extraordinary dry start to the water year was ranked as the second worst in downtown L.A.’s record books.

The extraordinarily dry conditions have kept vegetation flammable, an explosive combination during strong Santa Ana wind events that can rapidly spread embers if a fire breaks out.

Weather outlook after this storm

Light showers are expected over L.A. and Ventura counties by the late afternoon. There’s a chance of partly cloudy skies late in the afternoon for most areas, the weather service said, and the storm is expected to be mostly gone by late Monday.

On Tuesday, there’s a slight chance of afternoon showers in the San Gabriel Mountains.

Forecasters then expect dry weather later in the week. The weekend could bring clouds next weekend, and a slight chance of rain, although mainly to San Luis Obispo and Santa Barbara counties, the weather service said.