Voluntary and mandatory evacuation orders will go into effect in portions of Los Angeles County Wednesday amid fears of mud slides and torrents of debris down fire-denuded slopes as a result of the biggest storm to strike the Southland this rainy season.

The storm — something of a meteorological double-whammy: a strong Eastern Pacific weather system greatly bloated by an “athmospheric river” consisting of a subtropical plume of moisture — produced showers in Los Angeles County beginning Tuesday afternoon but won’t generate heavy rain in the county until late Wednesday evening, forecasters said.

The event is likely to produce 1 to 3 inches of rain in L.A. County Coastal and valley areas and between 2 and 5 inches in the mountains, said National Weather Service meteorologist Curt Kaplan, adding that rainfall expectations for L.A. County have been scaled down slightly since Tuesday, but Ventura and Santa Barbara counties are still expected to receive 2 to 5 inches of rain in coastal and valley areas and between 5 and 10 inches across the foothills and coastal slopes.

A flash flood watch will be in effect from Wednesday evening through late Thursday night not only in burn areas of Los Angeles County but also in urban areas. It will be in effect in the San Gabriel and Santa Monica mountains; the San Gabriel, San Fernando and Santa Clarita Valleys; Los Angeles, including the coast, metropolitan Los Angeles, downtown, and the Hollywood Hills; and both coastal and inland Orange County.

“In addition to the flash flooding and mud and debris flow risk in recent burn areas, there will be other flooding threats in non-burn areas due to the long duration and intensity of this storm,” according to an NWS statement.

“Widespread urban roadway flooding is possible as well as rockslides and mudslides, especially near canyon roadways. As a result, there could be significant travel delays and road closures across the region between Tuesday and Thursday night.”

The rain likely will stop late Thursday or early Friday, according to the NWS.

The NWS said rainfall rates up to six-tenths of an inch per hour are possible late Wednesday evening, possibly increasing to three-quarters of an inch per hour or higher at times Thursday. “Isolated rainfall rates as high as one inch per hour cannot be ruled out,” it added.

“Rainfall of this intensity can produce dangerous mud and debris flows near recent burn areas,” forecasters said. “Flash flooding is a very dangerous situation.

“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,” it said.

Duarte city officials said the city would adopt a “yellow alert” status at noon Wednesday in areas below the 2016 Fish Fire burn area. The alert calls for residents to move vehicles, trash bins and other large items out of streets to keep them clear for emergency crews and prevent items from being washed away.

The city also plans to close Mel Canyon Road to through-traffic below the burn area beginning at 6 p.m. The street will remain closed to at least 7 a.m. Friday. Valley View Elementary School, which is on Mel Canyon, will remain open, but students must be dropped off and picked up on Deerlane Drive.

Duarte officials will distribute filled sandbags to residents at the corner of Brookridge Road and Opal Canyon Wednesday. Empty bags and sand will also be available at Los Angeles County fire station at 1105 Highland Ave.

The Los Angeles County Fire Department advised people who reside in the areas affected by the La Tuna Canyon, Creek and Skirball fires to prepare for evacuations and street closures. Evacuations are anticipated to begin at 6 p.m. in the following areas:

–Voluntary evacuations were issued for the 9000 block of La Tuna Canyon Road to Sunland Boulevard; from Day Street (north border) to Plainview Avenue (east border) to Sherman Grove Avenue (west border).

–Mandatory evacuations in the Creek Fire and La Tune Canyon Fire burn areas include Kagel Canyon, Lopez Canyon and Little Tujunga. The 8300 block to the 9000 block of La Tuna Canyon Road also will be under a mandatory evacuation.

The city of Burbank, meanwhile, issued a voluntary evacuation order that will take effect at 8 p.m. and continue through at least 6 p.m. Thursday for the following streets in danger of flooding and mud flows due to the recent La Tuna Fire:

— Country Club Drive east of Via Montana;

— all of Hamline Place;

— Groton Drive east of Kenneth;

— 830-849 Stephen Road;

— Irving Drive between Kenneth and Joaquin;

— 2906 and 2934 Olney Place;

— 2934 Remy Place;

— 2949 Mystic View Place;

— 3430-3436 Brace Canyon Road;

— 3301-3310 Brookshire Court;

— 3318, 3321, 3322 and 3422 Wedgewood Court;

— 3514-3519 Folkstone Court; and

— 3529-3530 Castleman Lane.

An evacuation center will be established at Verdugo Recreation Center at 3201 W. Verdugo Ave. The center will not accommodate animals.

No-parking restrictions will also take effect at 8 a.m. on:

— Country Club Drive east of Via Montana;

— all of Hamline Place;

— Groton Drive east of Kenneth; and

— Bel Aire Drive from Cambridge Drive to Vista Ridge.

All of Burbank’s hiking trails have been closed, along with the Stough Canyon Nature Center and Wildwood Canyon recreation area, until further notice.

The NWS forecast rain in L.A. County Wednesday and relatively mild temperatures, including highs of 57 degrees on Mount Wilson; 62 in Lancaster; 64 in Palmdale and Saugus; 65 in Avalon; 66 in Burbank; 67 in Woodland Hills; and 68 in Downtown L.A., Long Beach, Pasadena, San Gabriel and at LAX. Temperatures will go down slightly amid more rain Thursday and remain in the 60s through at least Tuesday, including on days forecast to be sunny.

Rain was also forecast in Orange County, along with highs of 66 in San Clemente; 68 in Newport Beach and Laguna Beach; 70 in Yorba Linda; 71 in Fullerton; 72 in Mission Viejo and Anaheim; and 73 in Irvine. Temperatures will go down several degrees Thursday and remain in the 60s through at least Tuesday, including over four sunny days.

—City News Service

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