A storm system swollen with moisture from an atmospheric river will bring rain to Southern California Tuesday afternoon through Wednesday, prompting the National Weather Service to issue a flash flood watch for all burn areas in Los Angeles, Ventura and Santa Barbara counties.
Across Ventura and Los Angeles counties, the heaviest rainfall is expected late Tuesday evening and Wednesday morning, affecting the Thomas, Hill, Woolsey, Stone, South, Creek and La Tuna burn scars, according to the NWS.
Peak rainfall rates are expected to range between a half-inch and 0.80 inches per hour. There is the potential for isolated thunderstorms, which could produce higher hourly rates, forecasters said.
The flash flood watch will be in effect from 6 p.m. Tuesday until 11 a.m. Wednesday.
“Shallow mud and debris flows will be likely, especially in the first-year burn areas, with the potential for more significant and damaging debris flows. In addition, roadway flooding is likely, especially in low-lying areas, along with rock and mudslides on canyon roads and below steep terrain,” according to the NWS.
Los Angeles County officials warned residents in the Woolsey Fire burn area — where even small amounts of rain may cause significant mud and debris flows — to prepare for the possibility of evacuations, road closures and power outages. Residents were urged to identify two exit routes, make plans for pets and family members with special needs and pack an emergency kit with extra medication, important documents and warm clothing.
Additional sheriff’s deputies, firefighters and public works personnel will be on patrol in the area through Thursday morning, according to the county.
Authorities urged everyone to avoid crossing flowing streams or driving through flooded roadways.
The rain will turn to showers by Wednesday evening, then showery conditions will persist through Friday, according to the NWS. Dry weather is expected Saturday, and showers are possible Sunday through Monday.
Rainfall totals across eastern Ventura and L.A. counties should be generally 0.75 to 1.5 inches in coastal and valley areas, and 1.5 to 3 inches in the foothills and mountains. Through Friday, rainfall for Orange County is expected to range from one-half to three-quarters of an inch near the coast to 1.5 to 2.5 inches in the mountains, with local amounts to around 3.5 inches.
In the San Gabriel Mountains, a wind advisory denoting an expectation of 35-mph winds will be in force from 8 p.m. Tuesday to noon Wednesday amid south winds of 20-30 mph gusting at as much as 60 mph.
“Gusty winds will make driving difficult, especially for drivers of high-profile vehicles,” warned the NWS. “When driving, use extra caution. Be prepared for sudden gusty cross-winds.”
Snow levels will be high through Wednesday — generally above 7,500 feet, then drop.
In coastal waters, there is the possibility of isolated thunderstorms from this evening through Wednesday morning. The usual thunderstorm risks will be possible, including gusty and erratic winds, rough seas and the possibility of waterspouts.
Another upper low will drop southeastward through the eastern Pacific Sunday through Monday.
The NWS forecast rain in L.A. County Tuesday and highs of 57 on Mount Wilson; 60 in Avalon; 64 at LAX; 65 in Saugus and Long Beach; 66 in Downtown L.A., Lancaster; 67 in Palmdale, Burbank and San Gabriel; 68 in Woodland Hills; and 69 in Pasadena. Rain is forecast for Wednesday, followed by showers Thursday and Friday, sunny skies Saturday, and more showers on Sunday and Monday.
Partly cloudy skies are forecast in Orange County Tuesday, along with highs of 59 on Santiago Peak; 60 in Laguna Beach and San Clemente; ; 65 on Ortega Highway at 2,600 feet; 62 in Newport Beach; 66 in Fremont Canyon; 68 in Yorba Linda; 69 in Trabuco Canyon, Fullerton and Irvine; 70 in Anaheim; and 71 in Mission Viejo. Rain is expected in Orange County Wednesday, followed by showers Thursday, partly cloudy skies Friday, sunny skies Saturday, partly cloudy skies Sunday and more showers Monday.
More information on storm preparation is available at www.lacounty.gov/LARain. Road closures can be tracked at dpw.lacounty.gov/roadclosures or on Twitter at @CaltransDist7, @LASDHQ, @LHSLASD, @LACoFDPIO and @LACoPublicWorks.
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