(Bloomberg) -- A powerful Pacific storm knocked out power to thousands across California and is threatening heavy mountain snow and flooding rain near the coast before it moves across the country.

The storm could churn tornadoes in the US South and drop snow in the East by the end of the week. 

Snow piled up in Washington state, Oregon and California on Saturday, and an additional 2 feet (60 centimeters) could fall in the higher peaks of the Sierra Nevada range through Monday, the National Weather Service said. Southern California could get drenched Sunday with as much as 2 inches of heavy rain along the coast and valleys and 6 inches in the foothills.

The storm had knocked out power to 49,411 customers early Sunday, according to PowerOutage.us. On Saturday, California’s power grid operator issued a transmission emergency in the Humboldt area because of high winds, rain and heavy mountain snow.

The system will cross the Rocky Mountains, moving into the Great Plains on Monday into Tuesday, and “then it really intensifies,” said Marc Chenard, a senior branch forecaster at the US Weather Prediction Center. There’s an increased risk tornadoes, high winds and thunderstorms will break out across parts of Texas, Arkansas, Louisiana and Mississippi, according to the US Storm Prediction Center.

As the storm moves east it could bring heavy snow, as well as blizzard conditions from Montana to Minnesota, Chenard said. It could eventually drop snow from central Pennsylvania to northern New England at the end of the week. New York and the other large cities along the Interstate 95 corridor will likely get mainly rain.

--With assistance from Mark Chediak.

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