The storm next week is expected to bring ‘significant rain and hill snow’ to Southland, forecasts say


The National Weather Service says a storm system likely to receive widespread moderate to heavy rain in southern California during the second half of next week.

The rate of rain can be high at times, increasing the likelihood of debris flows in recently burnt areas, as well as falling mud and rock on mountain roads. Significant snow accumulation is possible with storms, mainly over 5,000 feet.

The largest storm, the third in a series, is predicted to involve an atmospheric river. Atmospheric rivers are a concentrated stream of water vapor in the middle and lower levels of the atmosphere. Because they are low in the atmosphere, they are hot, even when they are not directly piped to the tropics.

This atmospheric river will come more from the west, said Eric Bold, a coordinating coordination meteorologist with the National Weather Service in Oxford. “It’s not a direct tropical relationship, but [has] Above-normal water content that can bring continuous moderate rain for several hours. “

An atmospheric river is forecast to be the most powerful in a series of three storms.

An atmospheric river is estimated to be the most powerful in a series of three storms affecting the Southland through the weekend.

(Paul Daginsky / Los Angeles Times)

The change in pattern comes after summer, with record heat, the worst fire season in California history, and the drought and early winter plagued by Santa Ana studs.

After a hot summer, the entire state is unusually dry during the fall and early winter.

After a hot summer, the entire state is unusually dry during the fall and early winter.

(Paul Daginsky / Los Angeles Times)

Although the Pacific Northwest and Northern Intermountain West have enjoyed heavy rainfall from a series of North Pacific storms, the central and southern parts of the West are in drought that is as bad as it can be. Areas that have already been classified as extreme and exceptional droughts “may not present a lot of fall,” the US Drone Monitor reported on Thursday.

A wet pattern will provide welcome relief to the southwest.

A wet pattern would provide welcome relief to the southwest, which has been desolated by prolonged drought. The most recent data from the US Drought Monitor was released on Thursday.

(Paul Daginsky / Los Angeles Times)

The only way such a parched, scorched landscape can worsen would be to stop heavy rain from an atmospheric river – rain that is like a fire hose – washing up soil and debris beneath rugged slopes. Rain is needed, but not at once. If there is a heavy rain rate, there is a risk of debris flows in the recently burned trail, such as the Lake, Bobcat and Ranch 2 fires, and other fires in Orange County and the Inland Empire.

The forecasts do not anticipate an epic rain scenario, but warn that the public should focus on updating and follow officials’ instructions if they are asked to evacuate.

Heavy rainfall is not required to create a dangerous situation. For example, the Thomas Fire was followed by the Montecito Modslide in Santa Barbara County on January 9, 2018, with only half an inch of rain. But that rain fell in about 5 minutes, and produced debris 15 feet high.

A gentle storm in December prevented an otherwise dry fall and early winter in the city of Los Angeles.

A gentle storm in December prevented an otherwise dry fall and early winter in the city of Los Angeles.

(Paul Daginsky / Los Angeles Times)

How did we get to this point?
A la Nina is in place in the equatorial Pacific, and the rest is expected to persist through the winter. La Niña usually results in dry winters in Southern California and the Southwest, although this is not always the case. El Nino, La Nina’s waiter cousin, usually means a wet winter in Southern California based on history, but, again, there is no guarantee.

Southland has seen a storm in the past nine months, and the drought pattern so far corresponds to a typical La Niña winter – which also typically features wet-to-normal weather in the Pacific Northwest and in the northern-eastern season of the North Tier. is. United States of america.

Even though the Los Angeles area received almost normal rainfall last winter, the extreme summer heat and fall has left Santa Ana winds and fuel tinder dry in the early winter. Several large fires burned over 4 million acres in California in 2020, sometimes turning almost the entire state into smoke.

In Mediterranean climates such as California, it rains mostly during winter. Even without the influence of El Niño and La Niña, Southern California relies on five to seven significant storms for its rainfall each year.

“It doesn’t rain in LA or every day during the winter, as it does in Seattle,” meteorologist Bill Pattert said. “The rain comes in five, six or seven incidents. There is usually less than 20 days of rain, and all seasons receive less than 10 days of significant rainfall. “

The Los Angeles Basin is a floodplain. After the drought-onset season in 1937–38, two hurricanes fell in five days as sudden rain in the region in late February and early March 1938, as usually throughout the season. There is devastation from the foothills to Long Beach, causing a billion dollar loss in today’s dollars. Angelinos were fed up with such repetitive, flood damage. These events ultimately prompted authorities to lining the Los Angeles River and other waterways with concrete for flood control.

As Paetzert points out, these solid channels do not flow prominently about 99% of the time.

A reminder of what could happen before these waterways were built into concrete channels on the New Year in 1934.

In November 1933, a 7.5-square-mile area in the foothills above Montrose and La Crescenta caught fire. Then, on December 31, 1933, and January 1, 1934, an atmospheric river storm dropped 10 to 15 inches of rain on the foothills communities, and 20 to 30 inches over the foothills and mountains. As reported by The Times, Downtown Los Angeles received 8.27 inches of rain.

The fatal New Year's flood was front-page news in the Los Angeles Times.

The fatal New Year’s flood was front-page news in the Los Angeles Times.

(Los Angeles Times)

Local historian Art Cobri said, “The Montrose flooding, soon to be called a disaster, killed at least 45 people, destroyed about 100 homes and transformed the small community into a soil-filled, barren landscape gave.” Devastation and beyond, “the Times reported in 2009.

After the New Year's Flood in Los Angeles in 1934, cars are trapped in mud outside the Bohemian Gardens.

After the New Year’s flood in Los Angeles in 1934, cars are melted in mud outside the Bohemian Gardens on Mission Road. A man lost his life there.

(Los Angeles Times)

Singer-songwriter Woody Guthrie recalled the tragedy in a song about the “Los Angeles New Year’s Flood”.

Atmospheric rivers are extremely wet moisture rivers. They can dump rain on flat land as they come in the form of ash, but when they rise on steep and rugged coastal hills and mountains, the cargo of their moisture falls out. This means that they are releasing heavy rains, presumably at a rapid rate, with vegetation stripped by wildlife last summer and during fall.

“All this serves as a cautionary tale for those living under burnt areas like the Bobcat fire in the San Gabriel Mountains. Mudslides cannot be predicted, but they can be predicted, ”said Paitzert. Authorities issued a warning saying, “The best protection for mudslides is to stay informed and evacuate.”

“Great drought, fire, flood and heavy rain followed by flood, decade after decade. This is a story told for thousands of years, ”said Paizart. “This is a California classic.”

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