Southern California will be under the threat of severe weather on Saturday, the strongest storm surge to land over the weekend in Los Angeles County, bringing the risk of mudslides, debris flows and, possibly, tornadoes.
If rain falls as forecast, this storm could result in the city of Los Angeles seeing its wettest November since 1985. Heavy rain brings hills from Eaton and Mlobi.
A threat of severe weather is expected for most of Saturday, from midnight to 9 PM A flood watch will be in effect for Southern California from 4 am Saturday. Evacuation warnings are in effect at 11 a.m. Sunday for areas near the latest burning scars due to the risk of mud and debris. Warnings include areas near Palades, Eaton, Kenneth, Sunset and January’s wildfires.
But it remained unclear as of Thursday which areas will be hit hard by the storm. Rainfall rates on Saturday of 0.75 to 1.25 inches per hour are expected and a small group of land – about the width of California County. Enough rain to cause a landslide, which occurs when rain falls at the rate of half an inch or more per hour.
Forecasters do not yet know where that high rainfall will be concentrated.
“The problem is, we don’t know exactly which region” will be most affected, said Ryan Kittell, a neurologist with the national service office in Oxnard. “If you look at all our predictions, some of them like Ventura, some of them like Santa Barbara County. And at that time, unfortunately, in that way, unfortunately you just can’t say with certainty which is the emergence of Bulls-iso.”
If a band of heavy rain lines over La County, expect rainfall rates of about 1 inch per hour, Kittell said. If the band focused elsewhere, LA could still see an average of half an inch per hour, and resolutions would remain in place.
The area with the worst weather could see thunderstorms that could produce damaging winds or a tornado or two, Kitell said.
“While 99% of the area will not see such conditions, any part of our area, especially the coastal and valley areas, can,” said Kitell. “Consider changing any plans you may have on Saturday. Stay home and indoors.”
In case of lightning, he noted that it is better to stay inside away from windows. Those who must evacuate should not attempt to drive on a busy road.
There is still a chance that Saturday’s storm could be more impressive than expected. It is supported by the power of the “low cut,” which is so difficult to predict that it is called “Weathermanman’s woe.” Because the powerful low pressure system is fueled by the jet stream, “it’s just going to be around the top and that’s where it gets fun -” Kitell said.
Still, Kitell said, most of the more than 100 different computer forecasts suggest moderate to heavy rain. In the most likely scenario, Downtown La will receive 2.62 inches between Thursday and Sunday, which will cause flooding on streets and shallow ditches.
(National Weather Service)
To get that 2.62 inches of rain Downtown La would need to exceed 2.43 inches in November to break that 40-year-old record.
There is a 30% chance of a worst case scenario when Downtown La receives 4.81 centimeters with Debris Flows, the rapid swelling of the earth quickly pours down the hills and chooses not only mud but other debris that can move cars and crash into houses with deadly forces. A total of 4.81 centimeters will be one-third of the city’s annual rainfall.
Both mudflows and debris flows can be created by rain falling at a rate as low as half an inch per hour. But it depends on the burn scar, Kitell said. It would take rain falling at twice that rate — an inch per hour — to start running off some of the scars, he said.
The National Weather Service Office in Oxnard said Saturday there is a 70 percent chance the Eaton and Palisade burn scars will see 0.5 inches or more of rain per hour. There is a 38% chance of average rainfall of 1 inch or more per hour in those areas.
Rain is expected to begin falling Friday morning in Los Angeles, Orange, Riverside, San Bernardino and San Diego counties. Rain was forecast to begin Thursday in Ventura, Santa Barbara and San Luis Obispo Counties.
The heaviest rain in Southern California is expected late Friday into Saturday.
(National Weather Service)
Although tornadoes don’t usually hit California, they do happen. For the most part, “they’re weak, they’re short, and they usually don’t make a lot of news,” Kitell said. “But we get quite a few of them.” Sometimes they build on land, or they start as waterpouts – a storm in the sea – and then move to land.
“They’re not like the kind you used to hear in the midwest last 15, 30, or even an hour or two, and they’re a mile or two wide,” Kitell said. “We don’t have the nature for that,” yet they still pose a risk.
A five-minute tornado touched down in Santa Cruz County last December, damaging three trees, downed and power trees, overhanging trees and damaging road signs.
In this powerful storm this weekend, the river created a long group of rain that Thursday was shepherding across the Pacific Ocean to San Francisco. It was planned to move south and east as it went to Southern California.
The storm cut down trees in the San Francisco Bay area on Thursday and filled the grassy streets below. He was separated from a tree and fell from San Francisco’s Western Expressionar, colliding with a car, local news outlets reported. A tree fell over a fence in Santa Rosa. Rising water flooded part of the road just west of Charles M. Schulz-Sonoma County.
A Solo vehicle crash was reported on Highway 1 in Santa Cruz County, the California Highway Patrol said. A milling truck overturned on the highway between Watsonville and Gilroy, and all lanes of Moundway 17 connecting Santa Cruz and San Jose were closed for a while after the CHP Cruiser crashed; The CHP officer suffered minor injuries.
Rainfall amounts were impressive in the region, with San Francisco seeing 1.28 inches – that’s more than half of the average November rainfall. NAPA received 1.45 inches; San Francisco International Airport, 1.5; and San Rafael, 2.3 inches.
On Sunday, the high seas are expected to receive 2.38 inches; Redondo Beach, 2.48; Oxnard, 2.49; Thousand oaks, 2.63; Santa Clarita, 2.77; Covina, 2.89; and Santa Barbara, 4.21.
San Diego could get 2 to 2.5 inches; Riverside, San Bernardino, Escondido, and San Clemente, 2.5 to 3 inches; and Anaheim and Irvine, 3 to 4 inches, according to the Weather Service.
Even the desert can impress the rain. Palm Springs could get 1 to 1.5 inches, and Joshua Tree Pak Park could get 1.5 to 2 inches.
This storm will not be a major snowmaker in the mountains of southern California. Snow levels are expected to remain around 10,000 feet for the length of the storm, said Dave Munyan, a forecaster with the San Giego national office. By Sunday morning, snow levels will drop to about 7,000 to 7,500 feet, but by then, there won’t be much moisture left in the storm. Big Bear is forecast to get an inch of snow, and Idyllwild is expected to remain snowy, Munyan said.
“You’re going to get your snow accumulation — snow accumulation — on the highest mountain peaks,” Munyan said.
Winds from the south and east are expected to cause delays at Los Angeles International Airport on Friday and Saturday.
Looking into next week, the storm could return to southern California on Monday and Tuesday, with another roll on Thursday and Friday. Both storms are likely to have minor effects. But forecasters are looking at the second of the two storms, which could grow worse, Kitell said.
