An Atmospheric River, Or A Pineapple Express, Explained

Northern California is bracing for a heavy storm system that is expected to cause flooding across the region. This is a special type of storm, an atmospheric river, that is often referred to as a Pineapple Express.

Courtney Obergfell is a meteorologist with the National Weather Service.

She explains, “An atmospheric river is a narrow band of moisture that typically comes from the tropics, so usually near Hawaii, and then it makes its way to California and brings heavy rainfall to the area."

The atmospheric river forms over the Pacific Ocean and turns into a warm, dense funnel of rain, like a hose aimed at the West Coast.

The National Weather service has issued a flood watch across the region, especially near the Yuba and Cosumnes Rivers, which have fewer flood controls than the Sacramento River.  

Emergency officials are keeping an eye on the Yuba River, which is expected to rise quickly on Sunday and peak Monday because of the storm system.

Yuba County spokesman Russ Brown says there are areas along the river outside Marysville, near Linda, that are prone to problems.

"We're going to see those areas flood," says Brown. "There are a handful of business and homes in that area that will see water coming in."

Brown says they've been going door to door warning people near the river about the flood danger. He says the department believes most residents are prepared for rising water.

Sheriff's deputies have spent the last several months talking to homeless people and clearing them out of encampments along the river.

Brown says ranchers in the flood prone areas are used to it and most have already moved their livestock to higher ground.

The Sierra could see 10 to 15 inches of rain on Sunday, which will contribute to flood conditions in the foothills and burn scars.