Don’t put away your umbrellas just yet: More rain is expected in Los Angeles on Thursday, continuing an unusually early and wet start to the rainy season.
About half an inch to an inch of rain is expected in coastal and valley areas of Los Angeles County. While the rainfall won’t be as severe as the storm that swept through the area over the weekend, it could be severe enough to force the cancellation of outdoor activities, according to the National Weather Service office in Oxnard.
Rainfall totals are expected to increase in the foothills and mountains, around 1 to 2 inches.
Los Angeles County has a 10 to 20 percent chance of rain Thursday morning, but that will increase to 60 to 70 percent by the afternoon and 80 to 100 percent by evening. There’s also a 60 to 70 percent chance of rain Friday morning and a 30 to 50 percent chance of rain later Friday.
Showers in Los Angeles County may continue into Saturday morning, but the remainder of the weekend is “expected to be dry but cool,” the weather service said. The rest of Thanksgiving week is expected to be dry and warm, with highs in the 60s and 70s in many areas, the weather service said.
Thursday’s storm may do more good than harm, helping to further dampen the fall fire season. However, the rainfall may cause minor flooding of roads and trigger some landslides and mudslides, and ice and snow may appear on mountain roads.
And there’s still a chance (around 10 to 20 percent) that rainfall totals could be double the wider forecast.
This uncertainty is due to the nature of the storm, which is driven by a “cutoff low,” meaning it is isolated from the jet stream and spins unpredictably like a top, making it difficult to predict whether the system will slow down over Los Angeles and dump more rain than expected.
Forecasters said heavier downpours were possible in some areas. There is a three-fifths chance of half an inch per hour of rainfall between Pasadena and the borders of Los Angeles and Orange counties from 10 p.m. Thursday to 3 a.m. Friday.
Rainfall rates of half an inch or more create the risk of mudslides and mudslides.
A mudslide is a type of landslide that is caused when heavy rain begins rushing down a hillside, kicking up mud and debris. Small mudslides can cover roads and driveways, while large mudslides can cause boulders and cars to slide at speeds of up to 35 mph and send a wall of mud crashing into homes and businesses.
“While the overall risk of burn debris flow is low, it is certainly not zero,” the weather service said.
The latest storm is not expected to bring snow to the Grapevine section of Highway 5, which reaches an elevation of 4,144 feet at Tejon Pass.
But heavy snow is possible in large areas of the San Gabriel Mountains in Los Angeles County, including Baldy Mountain and Wrightwood Mountain, with wet snow accumulations up to 8 inches (elevation 6,000 feet). A winter storm watch is expected Thursday afternoon into Saturday morning.
Heavy snowfall could begin Thursday morning in the mountains of San Bernardino and Riverside counties, including Big Bell County, with 2 to 6 inches possible at 6,500 feet; 6 to 12 inches at 7,000 to 8,000 feet; and 12 to 18 inches above 8,000 feet. A winter storm watch is expected in the area Thursday morning into Saturday morning.
In Orange County, San Diego County and the Inland Empire, showers are expected to begin as early as Thursday morning and become more widespread and heavier Thursday night and Friday morning.
The San Diego Weather Service said thunderstorms are possible during this time.
A recent series of storms has resulted in wetter-than-usual rainfall across Southern California, significantly reducing the risk of wildfires and potentially bringing an early end to the annual fire season.
Since the start of the water year on October 1, downtown Los Angeles has received 4.89 inches of rain, five times the average for this time of year and one-third of the annual average. This time last year, only 0.07 inches had fallen since the start of the water year.
Forecasters say 3 to 4 inches of rain will be needed in lower elevations to effectively end Southern California’s high fire season.
In November alone, 3.48 inches of rain fell in downtown Los Angeles, nearly 10 times the average rainfall for that time of the month. It was the wettest November for downtown Los Angeles in more than 40 years, second only to 1982, when 4.41 inches of rain fell.
The wettest November on record for downtown Los Angeles occurred in 1965, when 9.68 inches of rain fell.
This November was also the wettest at the Santa Barbara Airport since records began in 1941, according to John Dumas, a meteorologist with the weather service’s Oxnard office.
The weather service said 8.42 inches of rain fell there. Dumas said this November just exceeded the airport’s 20 wettest calendar months on record.
Roads in Santa Barbara County were covered in mud and trees were uprooted by heavy rains over the weekend, but no major injuries were reported.
