California Winter Storm: Heavy Rain and Snowfall Cause Flooding, Mudslides and Travel Disruption Across North

A large winter storm system brought heavy rain and snow—as well as strong winds—to northern California on Tuesday, leading to flooding and travel disruption in several areas, along with mudslides and power outages.

The downpours are the result of a so-called "atmospheric river"—a long, narrow corridor of moisture—that is transporting water vapor from the Pacific.

"We're just getting an atmospheric river of rain coming in," National Weather Service (NWS) meteorologist Johnnie Powell told NBC News. "The Bay Area, Napa County, Lake County, Sacramento northward—that's where the main water hose is."

By Tuesday afternoon, many parts of Sonoma County had received several inches of rain, causing the Russian River to flood by the evening, according to the NWS. This prompted authorities to issue a mandatory evacuation order in the county, which affected thousands of people who live near the water.

"Sonoma County is recommending evacuations to residents living near the Russian River," the warning—which was issued yesterday—read. "The river is expected to reach flood stages (32 feet) today at 7 p.m. and is expected to crest at 45 feet at 10 p.m. Wednesday night in Guerneville."

Should the river reach 45 feet, many buildings in the town of Guerneville—which lies around 75 miles north of San Francisco—could be flooded, The Associated Press reported.

"We're definitely in high concern mode," Sonoma County sheriff Spencer Crum told AP. "We're bringing our boats out here and we're letting the public know to take this one serious."

There were further reports of flooding from around the San Francisco area and Santa Rosa, causing travel disruption on the roads, AccuWeather reported.

Flood warnings were also issued on Tuesday for the Navarro, Eel, Napa and Carmel rivers, NBC News reported.

Meanwhile, the NWS issued an urban and small stream flood warning for an area stretching from Stockton to Redding. The alert advises drivers never to cross flooded roads, while urging residents to be aware if they live near streams and creeks.

The heavy rain even caused a mudslide in the town of Monte Rio—located on the banks of the Russian River—which trapped motorists and cut off a highway that residents were using to escape the flooding, SFGate reported.

Furthermore, Tuesday's downpour even broke records in one location. Santa Rosa logged 5.66 inches on Tuesday—a one-day rainfall record, according to the NWS. It also led to the cancellation of more than 150 flights at San Francisco International Airport, The Weather Channel reported.

Aside from the rain, Northern California also experienced heavy snowfall at higher elevations, making travel extremely difficult in some areas. For example, a large section of Interstate 80—which runs through the Sierra Nevada—was closed Tuesday afternoon, according to Caltrans District 3.

Currently, more than 35,000 homes and businesses are without power in Northern California, according to poweroutage.us, likely as a result of the storm.

Meteorologists say there will be no let up from the storm over the course of Wednesday as it moves over Northern California into Oregon and the interior of the United States, raising the risk of more flooding, heavy snowfall, mudslides and travel disruption.

"As the storm track centers on Northern California through midweek, a general 4-8 inches of rain will fall along the northern coast of California and lower west-facing slopes of the Sierra Nevada through Wednesday," AccuWeather Senior Meteorologist Kristina Pydynowski told the site.

Many areas of Northern California at lower elevations will likely see between 1 and 3 inches, according to Pydynowski, although some parts could see as much as 14 inches by Wednesday night, Powell said, NBC News reported.

According to Pydynowski, 4-8 feet of snow could fall in the central and northern Sierra Nevada through Wednesday night, while the southern Cascades could see around 2 feet. This is likely to lead to more severe disruption on mountain roads, particularly interstates 5, 80 and 84. Thus, authorities are warning people not to travel through the mountains unless it is absolutely necessary.

"Extremely heavy mountain snowfall is expected through Thursday," NWS Sacramento said in a Tweet. "Mountain travel is HIGHLY DISCOURAGED! If you must travel, be prepared for hazardous travel conditions, significant delays, chain controls, & possible road closures. Bring winter clothes & extra food & water."