Torrential downpours and damaging winds left tens of thousands of homes and businesses without power in northern California on Friday even as the area braced for the next onslaught of severe weather later in the day and through the weekend.

The next system of heavy downpours was expected to dump 3 to 6 inches (15 cm) of rain on the region, potentially causing scattered flash flooding and mudslides in areas where the soil was already saturated, the National Weather Service (NWS) said in its forecast.

Much of the northern two-thirds of California, the most populous state in the nation, was under flood, gale-force wind and winter storm warnings on Friday as forecasters urged residents to prepare for flooding and to stay off the roads.

In addition to heavy rains, one to three feet of snow was expected to fall during the weekend in the Sierras, where snow accumulations of a foot to 18 inches or more were measured earlier this week, the weather service said.

The ominous forecast comes on the heels of a massive Pacific storm that unleashed high winds, torrential rains and heavy snow across the region for two days. As of Friday morning, some 60,000 homes and businesses remained without power because of the weather, according to data from Poweroutages.us.

Strong winds uprooted trees, already weakened by drought and poorly anchored in rain-soaked soil, knocked down power lines and blocked roadways across the region.

The storm was powered by two overlapping phenomena – an immense airborne stream of dense moisture from the ocean called an atmospheric river, and a sprawling, hurricane-force low-pressure system known as a bomb cyclone.

The blast of extreme winter weather marked the third and strongest atmospheric river to strike California since early last week. Research predicts that climate change will cause atmospheric rivers to become larger and carry more water.

At least six people have been killed in the severe weather since New Year’s weekend, including a toddler killed by a fallen redwood crushing a mobile home in northern California.

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