Atmospheric river will continue to drench portions of California, forecasters say
An atmospheric river is slamming portions of California, with multiple inches of rain expected to drench the area until the storm runs out of moisture Wednesday morning, forecasters say.
According to the National Weather Service's Tuesday morning forecast, the atmospheric river is expected to "gradually settle southward through the middle of the week as multiple waves of low pressure traverse the front and bring strong Pacific moisture transport" into the coastal ranges, portions of the Central Valley, and the foothill of the Sierra Nevada.
The weather service said this moisture will result in more heavy rain for the region, with concerns for flooding which also includes the Bay Area.
"An additional 2 to 4 inches of rain is expected for the coastal ranges, with 3 to 6+ inches for the Sierra Nevada foothills," the NWS said Tuesday. The Weather Prediction Center has maintained a Slight Risk (level 2 of 4) of excessive rainfall across the region to account for this, the weather service said.
A Flood Watch is in effect for the Bay Area and Central Coast until 4 a.m. local time Wednesday, according to the NWS office in San Francisco, as excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations, as well as in areas of poor drainage and urban areas.
The NWS office in Sacramento said Tuesday "widespread participation is expected to return today through the middle of the week as the next weather system moves through the region." Some areas near Sacramento could see as much as 6 inches of rain, the weather service said.
The weather service is urging residents to monitor later forecasts and be alert for possible Flood Advisories/Warnings.
"Those living in areas prone to flooding should be prepared to take action should flooding develop," the NWS said Tuesday.
What is an atmospheric river? What about a Pineapple Express?
Atmospheric rivers are long, narrow tracts of the Earth’s atmosphere that gather moisture from the tropics near the equator and sweep it toward the poles.
According to the National Oceanic and Atmospheric Administration, atmospheric rivers can vary greatly in size and strength, however the average atmospheric river carries an amount of water vapor "roughly equivalent to the average flow of water at the mouth of the Mississippi River." Strong atmospheric rivers can transport up to 15 times that amount.
"When atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow," the NOAA said.
A Pineapple Express is a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the West Coast of the United States.
Gabe Hauari is a national trending news reporter at Paste BN. You can follow him on X @GabeHauari or email him at Gdhauari@gannett.com.