(Bloomberg) -- Torrents of rain and heavy mountain snows are expected to sweep across California at the end of the week, raising the risk of floods and mudslides on a region that’s already drenched.

The state is still getting snow from a weekend storm that’s winding down, creating an avalanche threat in the eastern Sierra Nevada, the National Weather Service said. A more powerful storm, called an atmospheric river, is forecast to roll in from the Pacific Ocean later this week, bringing heavy rain to some of the same areas, said William Churchill, a forecaster for the US Weather Prediction Center, an arm of the weather service.

“That will be starting Thursday and kicking into high gear Friday into Friday night,” Churchill said.

• Read more: California Reels as ‘Rivers’ in Sky Morph From Blessing to Curse

California was slammed with a series of these storms from late December to early January. Flooding and heavy snows killed at least 19 people, caused billions of dollars of damage and sparked widespread power outages. However, the storms are also crucial to providing California with the water it needs to make it through the year. The most populous state gets most of its rainfall from November to March and relies on heavy snow in the mountains to create a massive frozen reservoir that crucial in spring and summer when it melts.

Those storms, along with several smaller ones in recent weeks, have helped California begin to emerge from a three-year drought. Last week the amount of land in drought across California dropped below 50% for the first time since 2020, according to the US Drought Monitor.  

The Pacific storms are called atmospheric rivers and can transport as much water as flows from the mouth of the Mississippi River. While these storms can be beneficial to California’s water supply, if they arrive with warm temperatures they bring mainly rain that can cause mudslides and floods and erode the snowpack. 

©2023 Bloomberg L.P.