Floods and landslides are hazards like fire la gird and cold rain

Areas recently burned by wildfires in Los Angeles County are at some risk for flooding and landslides as southern California prepares for its first critical weekend of winter.

“The threat is high enough to prepare for the worst,” the National Weather Service office in Oxnard said on social media.

Forecasters say there is now a 10% to 20% chance of severe flooding and road washouts in the most vulnerable areas later, namely, the pacific burn areas and Malibu, the Eaton fire around Altadena and Pasadena, the HUZES fire around Dataic Lake, and the bridge fire in the Angele National Forest north of Glendora.

The Bridge Fire burned more than 56,000 acres in Los Angeles and San Bernardino, in the fall, destroying 81 structures and injuring eight firefighters.

Based on US Geological Survey research, these scorched areas have the potential for significant debris flows, said Ryan Kitell, a meteorologist.

“They are some of the burning scars. They are close to communities and / or vulnerable infrastructure. And the direction of the area was looking for those places, in particular, to have high chances, high power, for those high people and intensity of rain, said Kitell.

The chance of flooding and runoff in those recently burned areas, released Friday afternoon, comes from the 5% to 10% chance predicted the day before. “While damaging debris flows are not a likely outcome, there are still many uncertainties about this storm,” the weather service said.

Recently burned areas are vulnerable to flood damage and global warming because the heat from the fire makes it difficult for water to penetrate the top layer of soil. The soil becomes water, then it starts to flow up and down and pick up rock and debris.

That can lead to “Mnumlolozi,” where the water starts to run only on muddy hills, usually meters of water that destroys and is killed by thick rocks and where it pulls rocks, branches and sometimes maspive walls. Mudflows and debris flows are types of landslides.

“The potential outcome is that you don’t have a significant waste flow, but there’s a very high potential to increase that it’s definitely there, it’s on the table,” Kitell said. The possibility of debris flows “is still a threat that people should at least plan and consider.”

“The most likely outcome is that there would be a shallow debris flow with kind of minor impacts,” Kitell said.

Time

Forecasters with the weather service have issued a 24-hour high risk flood watch – from Sunday at 4 PM to Monday at 4 PM

Sunday night will be the time of highest concern, said meteorologist Ryan Kitell.

A flood watch is issued when the weather is too favorable for flooding. “It doesn’t mean flooding will happen, but it’s possible,” the weather service said.

Among the Weather Service’s recommendations: Avoid an area that has recently been burned at that time. Use sandbags to protect the property. And residents who decide to stay can ‘keep shopping’ when street access is restricted. “

(National Weather Service)

A scheduled flood watch did not include the Burn Scar mountain fire in Ventura County.

A chance of rain begins to pick up Saturday afternoon in Los Angeles and Ventura Counties, and a period of heaviest rain is expected by Sunday afternoon in Los Angeles and Ventura Counties. It will be normal for the rain to appear light, and come and go every weekend into Monday.

This is “a slow-moving storm, so it’s going to be stubborn. It’s going to stick around,” said Alex Tardy, a meteorologist for the National Weather Service in San Diego. “It’s going to send waves of moisture on Monday. So I think that’s going to add up to a lot of rain and snow.”

Forecasters have raised their predictions for how much rain could fall. The adjusted weather is the result of a low pressure system, coming down from Canada, it seems to be a little veer to the west – less on the coast of southern California – than before, which will make this storm in the water.

That results in ‘more concern for debris flowing into other burn scars,’ Kitell said.

(National Weather Service)

The mountains of Los Angeles and Ventura Counties could get 1 to 2 inches, while half an inch to 1 inch is possible elsewhere.

Between Saturday and Monday, Oaks and Oxnard thousand received three buckets of rain; Redondo Beach, Santa Clarita and Carlimore, seventy – seventieth of an inch; Long sea, and fifteenth of an inch; and Downtown Los Angeles and Covina, nine-ninths of an inch.

If the storm produces rain at the upper end of the scale, from 1 to 1.5 inches of rain could fall in Orange County, Ontario, Riversula, Lake Elsinore, Tempecula and Northern San Diego County. From 0.7 to 1 inch of rain may fall in San Diego, and from 1.5 to 2 inches in San Bernardino.

The rain is expected to snap a record, or record, streak of dry weather for southern California. Many areas of the region received less than 5% of the accumulated rainfall of this point in the water year, which began in Oct. 1.

Downtown Los Angeles has received just 0.16 percent of rainfall since Oct. 1, which is 2% of the average for this time in the water year – 6.48 centimeters. The annual rainfall for the city of Downtown is 14.25 inches.

Southern California is now in “extreme drought” or “severe drought,” according to the US drought.

Chance of thunderstorms, and risk of flooding

There is a 15% to 25% chance of thunderstorms anywhere in Los Angeles, Ventura, Santa Barbara and San Luis Obispo included in this rain event. With that comes the possibility, in remote areas, of rainfall rates of one-half of an inch per hour to three inches per hour.

That’s important, because rainfall amounts in the half inch per hour during the first hour when debris flows can be created in newly burned areas. If the rainfall amounts are above this figure – and they happen to come directly from the hot area – “That’s where we could get some interesting and some important swearing,” said Kitell.

“Most areas won’t see this much rain, but expect a few areas,” Kitell said. “It’s very difficult, if not impossible, to predict exactly which areas will see those numbers.”

Average rainfall rates across the region are expected to be 1/10 of an inch per hour to 1/2 of an inch per hour, Kitell said. That should have beneficial side effects.

If the rain falls with an intensity of one quarter of an inch per hour and half an inch per hour, it tends to get flooding in cities and water bodies, said Tardy, which can, he said, force other roads or a traffic road will be closed.

There could be a significant cut, coming from the South, Kitell said. Wind gusts of 15 mph to 30 mph could hit at times over the weekend, and up to 60 mph in the Antelope Valley. That could lead to flight delays, including at Los Angeles International Airport, and dangerous driving conditions, with the possibility of power outages and falling trees.

There is also a slight chance of hail.

Snowfall

Snow levels can fall 3,500 feet above sea level, and six to 12 inches can fall on San Gabriel Mountain. There could be 1 to 2 inches on the Grapevine portion of Interstate 5, and the Tejon Pass, but there could be less or more, Kitell said.

Big Bear Lake and Wrighwood saw 12 to 18 inches of snow, Tardy said.

“Mt. Baldy – which has been really suffering this year – could get a few feet of snow … maybe up to 3 feet, depending on if this storm moves as slowly as expected,” said Tardy.

For most of this storm, there will be light snow, but there could be a period between Sunday afternoon and Monday morning when the snow could have moderate snow intensity, Kittell said. Expect frozen and snow-covered roads in the mountains “with delays, and possibly some localized closures,” Kitell said.

This will be one of the first winter storms of the season, Tardy said, following the first that arrived Jan. 7 coming from the north, he brought just a few centimeters.

“This one will be widespread again [get to an] Even the low altitude,” Tardway said.

Some hot spots are forecasters to be hired

Elsewhere in southern California, meteorologists will also closely monitor the burned area of ​​the 43,978-acre Fire in San Bernardino County, which started in the city of Pearland Bernardino, which spread to one building.

The line fire burned all the way to the end at 8,000 feet above sea level, Tardy said.

Also highly regarded is the 23,526-acre airport hot spot at the Orange and Riverside Airport. The airport fire, which destroyed 160 structures, burned its way through the Santa Ana mountains and burned in Santiago Peak, which rises about 6,000 meters above Orange County.

Long weather

By February, Northern California saw the return of winter storms. But southern California could remain dry early in the month, Tardy said.