A strong late-season Pacific storm brought more wind, rain and snow to saturated California on Tuesday as the first full day of spring showed little change from the state's extraordinary winter.

Forecasters said the storm would focus on the southern half of the state, bringing threats of heavy runoff and mountain snowfall measured in feet.

Ponding water shut down multiple lanes of U.S. 101 in downtown Los Angeles before dawn, and there were numerous reports of cars being disable by freeway potholes.

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Historic Sierra Snow

Working inside a nearly 18-foot-deep snow pit at the UC Berkeley Central Sierra Snow Lab, from left, Shaun Joseph, Claudia Norman, Helena Middleton take measurements of snow temperatures ahead of a weather storm on March 9, 2023, in Soda Springs, California. (Karl Mondon/Bay Area News Group via AP)

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The National Weather Service said the storm is a Pacific low pressure system interacting with California's 12th atmospheric river since late December.

California's unexpected siege of wet weather after years of drought also included February blizzards powered by arctic air.

The storms have unleashed flooding and loaded mountains with so much snow that roofs have been crushed and crews have struggled to keep highways clear of avalanches.