A “strong atmospheric river” has started bringing rain to Northern California, according to the Center for Western Weather and Water Extremes.
Atmospheric River Impacts
The rain began late Monday, February 23 and is expected to move into Central California throughout Tuesday, February 24. With warmer temperatures, the precipitation is likely to fall as rain. Freezing levels in the northern Sierra Nevada are forecast to remain above 8,000 feet, potentially reaching 10,000 feet.
The atmospheric river is “associated with a poleward surge of tropical and subtropical moisture from the Northeast Pacific” and is expected to dissipate by Wednesday, February 25.
What is an Atmospheric River?
According to the National Oceanic and Atmospheric Administration, atmospheric rivers are long, narrow regions in the atmosphere that carry most of the water vapor outside of the tropics. The average atmospheric river carries an amount of water vapor roughly equivalent to the flow of water at the mouth of the Mississippi River, but exceptionally strong ones can carry up to 15 times that amount.
Meteorologist Katrina Hand of the National Weather Service’s Sacramento office stated the “warm storm system is already moving into the area.” Scattered showers were reported across the northern San Francisco Bay Area overnight Monday, February 23. Showers are expected to expand across the San Francisco Bay Area and into the Monterey Bay area Tuesday evening, then slowly spread into the Central Valley and the Sierra Nevada throughout the day.
Precipitation is expected to taper off overnight Tuesday, with lingering showers over the Sierra Nevada mountains Wednesday morning. The weather is forecast to be drier through Saturday, though a weak system may approach the area later in the weekend, potentially bringing very light, scattered precipitation.
Frequently Asked Questions
What is an atmospheric river?
“Atmospheric rivers are relatively long, narrow regions in the atmosphere — like rivers in the sky — that transport most of the water vapor outside of the tropics,” according to the National Oceanic and Atmospheric Administration.
When do atmospheric rivers typically impact California?
“The most frequent and significant atmospheric rivers” in California happen in December, January and February, according to the Center for Western Weather and Water Extremes.
What is the current forecast for the precipitation type?
With the warm nature of the storm, the predicted precipitation will likely fall as rain, according to the Center for Western Weather and Water Extremes.
As this atmospheric river moves through California, how will communities balance the need for water resources with the potential for flooding?
