Los Angeles - The most recent storm surge of heavy, wind-driven rain and snow churned into California on Tuesday, causing scattered floods and mudslides, uprooting trees, and issuing evacuation orders to thousands of storm-weary residents.

The latest onslaught, which arrived early on the second day of spring, was mainly focused in Southern California, the state's central coast, and its agricultural heartland, which were still drenched from a relentless string of storms that started in late December.

High wind advisories and warnings were issued for a wide area that included Los Angeles, the border with Mexico, and the San Francisco Bay area. High mountains were under winter storm warnings, and several feet of snowfall were anticipated.

The majority of greater Los Angeles and a sizable portion of western and central Arizona were among the areas in which the National Weather Service (NWS) issued flood watches to a population of more than 17 million people.

According to Frank Pereira of the NWS Weather Prediction Center, sustained winds of 60 to 70 miles per hour (97 to 113 kilometres per hour) were a greater threat in the Santa Cruz and Bay areas, toppling trees and power lines.

A person killed in a car by a falling tree in Sonoma County, north of San Francisco, was at least one wind-related fatality, according to Pereira.

According to Diana Crofts-Pelayo, a spokesperson for the California Office of Emergency Services, more than 14,000 people were ordered to seek higher ground due to flooding, with evacuation warnings issued for another 47,000 residents.

The majority of the evacuation orders, covering approximately 12,000 people, were issued in Tulare County, a flood-prone region in the San Joaquin Valley where high water from recent levee breaches has inundated a number of communities, according to Crofts-Pelayo.

Otherwise, flooding on Tuesday was mostly confined to the south. According to Pereira, they included the rescue of a motorist whose vehicle was swept away in a flooded stream and the recovery of an SUV from a mudslide in San Diego County.

According to the utility outage tracking service PowerOutage.us, nearly 250,000 homes and businesses were without power across the state.

To prevent populated areas from flooding, emergency teams across the state patrolled rain-swollen streams, repaired damaged levees, and cleared debris from storm drains and culverts.

Crews in San Luis Obispo County were on high alert for Lopez Reservoir to reach full capacity for the first time in 25 years and spill over into an adjacent creek that runs to the seaside town of Oceano and is bounded by a weakened levee, according to Rachel Monte Dion, a county emergency services coordinator.

If the levee is overtopped to the north instead of the south as designed, it could flood the homes of about 1,500 Oceano residents, she said.

High winds, heavy rain, and snow were expected to spread across the southwestern United States into the central Great Basin and Rockies by late Tuesday and last through Wednesday night, according to the NWS.

The storm was the 12th so-called "atmospheric river" to hit the United States' West Coast since December, formed by an enormous airborne current of dense water vapor carried aloft from the ocean and flowing overland in bouts of heavy rain and snow.

The latest system was driven by a Pacific cyclone swirling around an intense low-pressure system off the coast of San Francisco, sucking up massive amounts of moisture and channeling it to the coast.

Unlike previous atmospheric rivers this season, the latest brought a cooler load of moisture, resulting in more snowfall in the coastal mountains and Sierra Nevada range.

At elevations above 6,000 feet, where some areas are still blanketed in snow from last month, up to 4 feet (1.2 meters) of snow was forecast.

The NWS predicted up to 3 inches (7.6 centimeters) of rain in Southern California's coastal regions and valleys and up to 6 inches in the lower mountains and foothills.

The rapid succession of Pacific storms over the last three months has come as a surprise to a state that has been plagued by drought and wildfires in recent years—a shift in weather extremes that experts say is symptomatic of human-caused climate change.

California's harsh winter has caused widespread property damage and upheaval for thousands of residents, with storms responsible for more than 20 deaths.

However, the abundance of precipitation has replenished severely depleted reservoirs as well as the state's mountain snowpack, both of which are critical sources of drinking water, irrigation, and food for fish and wildlife.