A major storm began to flood Northern California on Sunday bringing up to ten feet of snow at higher elevations before moving south on Monday and Tuesday.
Forecasters said the southern California storm would be “significant,” with up to 3 inches of rain in coastal areas and up to 5 inches in the foothills and mountains.
“We expect a bit more rain in Los Angeles after midnight on Monday and through Tuesday morning,” said Mike Wofford, a meteorologist with the National Weather Service in Oxnard.
One to 3 feet of snow is expected in mountains above 7,000 feet, with a few inches being possible to a depth of 4,500 feet.
“Ski resorts will do well,” said Woofford.
The storm will usher in lower temperatures, with highs in the 50s on Monday and Tuesday and lows plummeting into the 30s on Tuesday night in the mountains and parts of the San Fernando Valley.
Nighttime temperatures could drop to the 20s in Antelope Valley, where officials are forecasting gusts of wind of up to 40 to 65 miles per hour.
Coupled with the storm are potential travel delays, the potential for debris flows in the recent burn areas, local flooding, mud and rock slides on mountain roads, and dangerous winter driving conditions in the mountains at an altitude of approximately 2,000 feet, the weather service said.
In Northern California, an atmospheric river broke through the San Francisco Bay Area on Sunday morning and is expected to deliver the heaviest rain from Sunday night to Monday.
Forecasters said they expect the frontline moving through the Bay Area to grind to a halt over Santa Cruz on Sunday evening, causing increased rainfall and flooding concerns in the recent burn scars.
At higher elevations, there could be more than six inches of rain, with some parts of the Santa Lucia Mountains reaching up to 10 inches, the weather service said.
Forecasters said they were also concerned about the potential for fallen tree branches and fallen power lines when strong winds blow through.
But officials said the storm that is sweeping the bay is “nothing like the snowy weather that will hit the Sierra Nevada.
Late Sunday morning, snow pelted portions of Freeway 5 north of Redding and was supposed to spread southeast into the southern Cascades and the northern Sierra. The weather service forecasts “enormous accumulations of snow at the pass height with the standards required for snow measurement”.
“There will be a lot of snow up there. We can get 110 to 120 inches over 8,000 feet, ”said Amanda Young, a meteorologist for the National Weather Service in Reno. “The worst will be early in the morning Monday through Tuesday.”
Our crews work hard to keep the roads free and safe for the traveling public. If you are planning to travel during this storm please make sure you have chains in your vehicle, drive according to conditions, stay vigilant and drive safely around our crews. pic.twitter.com/AOmshBmO2z
– Caltrans District 2 (@ CaltransD2) December 12, 2021
The heavy snowfall will create significant travel delays with “extremely difficult to impossible journeys over the mountains,” officials said, accompanied by strong winds that affect visibility and create potential whiteout conditions.
The Mammoth Mountain ski area has alerted skiers and snowboarders to the potential for heavy snowfall and strong winds for the next few days.
“If you plan to travel to the area during this time, please plan ahead and contact CalTrans for real-time chain control information and road conditions,” the resort said on Facebook. “This storm is going to be a big one – stay safe, plan ahead, obey all closings, and enjoy a classic High Sierra storm.”
The National Weather Service in Sacramento does not recommend travel because chains are required on many mountain roads.
In some parts of Shasta County, 5 to 6 feet of snow could be above 5,000 feet, with more than 6 feet being possible at higher elevations in Lassen and Sierra Counties.
A second weather system could bring more rain and snow on Wednesday and Thursday.
“After this storm we will need a new color scale for our snow forecast maps,” tweeted the weather service.