A powerful storm has brought heavy rain and snowfall to much of California, causing traffic jams and closing major roads as the state prepares to usher in a new year.

In the high Sierra Nevada, as much as 2ft of snow could accumulate into early on New Year’s Day.

The US National Weather Service in Sacramento warned about hazardous driving conditions and posted photos on Twitter showing traffic on snow-covered mountain passes, where vehicles are required to have chains or four-wheel drive.

The so-called atmospheric river storm was pulling in a long and wide plume of moisture from the Pacific Ocean. Flooding and rock slides closed portions of roads across Northern California.

The California Highway Patrol said a section of US 101 – one of the state’s main traffic arteries – was closed indefinitely south of San Francisco because of flooding.

Videos on Twitter showed muddy water streaming along San Francisco streets, and a staircase in Oakland turned into a veritable waterfall by heavy rains.

Weather service meteorologist Courtney Carpenter said the storm could drop over an inch of rain in the Sacramento area before moving south.

Flooding in California
Pedestrians carry umbrellas as they walk in the rain in Stanford, California (AP)

One ski resort south of Lake Tahoe closed chair lifts because of flooding and operational problems, and posted a photo on Twitter showing one lift tower and its empty chairs surrounded by water.

The Sacramento agency released a map of 24-hour precipitation through Saturday morning, showing a wide range of totals in the region, from less than an inch in some areas to more than 5in in the Sierra foothills.

The Mammoth Mountain Ski Area reported numerous lift closings, citing high winds, low visibility and ice.

The Stockton Police Department posted photos of a flooded railroad underpass and a car that appeared stalled in more than a foot of water.

Winter Weather California
Snow on US Route 50 in South Lake Tahoe California (San Francisco Chronicle via AP)

The rain was welcomed in drought-parched California, but much more precipitation is needed to make a significant difference. The past three years have been California’s driest on record.

A winter storm warning was in effect into Sunday for the upper elevations of the Sierra from south of Yosemite National Park to north of Lake Tahoe, where as much as 5ft of snow is possible atop the mountains, the National Weather Service said in Reno, Nevada.

A flood watch was in effect across much of Northern California through New Year’s Eve. Officials warned that rivers and streams could overflow and urged residents to get sandbags ready.

Some rainfall totals in the San Francisco Bay Area topped 4in.

The state transportation agency reported numerous road closures, including Highway 70 east of Chico, which was partially closed by a slide, and the northbound side of Highway 49, east of Sacramento, which was closed because of flooding. In El Dorado County, east of Sacramento, a stretch of Highway 50 was closed because of flooding.

California Storms
A rockslide near the McCoy Creek Bridge in Mendocino County, California (Caltrans District 1 via AP)

Humboldt County, where a 6.4 magnitude earthquake struck on December 20, also saw roadways begin to flood, according to the National Weather Service’s Eureka office.

A bridge that was temporarily closed last week due to earthquake damage may be closed again if the Eel River, which it crosses, gets too high, officials said.

It was the first of several storms expected to roll across California over the next week. Hannah Chandler-Cooley, a meteorologist at the National Weather Service in Sacramento, said the current system is expected to be warmer and wetter, while next week’s storms will be colder.

The Sacramento region could receive a total of 4 to 5 inches (10 to 13 centimeters) of rain over the span of the week, Ms Chandler-Cooley said.