California Faces Atmospheric River Deluge With up to 21 Inches of Rain
A strong and prolonged atmospheric river is expected to affect northwest California this week, with moderate to locally heavy rainfall bringing the potential for rapid rises in rivers, streams and creeks across the region, the National Weather Service said.
The atmospheric river—a narrow corridor of concentrated moisture originating from the Pacific —marks one of the strongest storms to hit the region this season. The river storm is expected to bring a deluge of torrential rain, flooding and hazardous conditions to the region later in the week.
Over the weekend, an atmospheric river hit the Pacific Northwest , with a second round of heavy rain and snow arriving earlier this week. Poor weather conditions are also expected in Oregon and Washington through Thursday.
On November 15, the Center for Western Weather and Water Extremes highlighted the potential for this event to reach an AR4 or even AR5 on its scale—signifying a strong to extreme atmospheric river—especially along the southern Oregon coast.
Meteorologists warn that storm amounts of rainfall could easily reach between 6 and 14 inches over four days, with up to 21 inches predicted for the King Range, posing significant risks to communities and infrastructure.
Last winter, the West Coast faced a slew of atmospheric rivers that caused devastating floods and landslides. However, the storms also brought a deluge of rain that supplemented California's lakes and rivers, helping to eliminate the state's drought.
If the atmospheric river hits as expected, the northern portions of the North Bay would likely take the brunt of the atmospheric river, but those impacts could shift slightly southward closer to the San Francisco Bay, Fox News reported.
Cities on the North Coast could be deluged with over 10 inches of rain, while San Francisco and Oakland could get 1 to 4 inches, according to the National Oceanic and Atmospheric Administration weather prediction webpage, Fox reported.
Rain will be heaviest on Wednesday, the NWS said, with 2 to 4 inches of rain, while high peaks in the King Range could see 6 to 9 inches of rain over 24 hours.
The agency predicted more moderate but persistent rain to continue Thursday through Saturday, with a likely rainfall of 1 to 3 inches each day.
However, the forecast is more uncertain further out. Long-range models show the potential for rain to continue into the week of Thanksgiving .
Newsweek contacted the NWS for comment on Monday via email outside normal working hours.
The greatest risk is for Humboldt and Del Norte Counties, where soils are already near saturation, the NWS said. Significant rain is also expected in Mendocino and Lake Counties, though drier soils should reduce the flood risk.
Much of the precipitation in Trinity County will likely fall as snow, with snow levels in the eastern half of the county as low as 2,500 feet, the agency said.
The NWS has warned of the risk of flooding in the region, especially for the northern half of the area, where previous rain events have already saturated soils.
It added: "Expect flooding in low lying areas, areas with poor drainage, and increased risk of debris on roadways. Rivers, streams and creeks will rapidly rise. The Eel River is around 20 percent chance of exceeding flood stage Thursday evening.
"The Mad River and the Russian River are showing 5 to 10 percent of reaching flood stage."
Residents in affected areas are advised to follow the weather forecast over the next few days, as forecast confidence and details will likely increase. Beyond rain, the storm is expected to bring widespread damaging wind.
Emergency alerts, evacuation resources and real-time updates can be accessed through the NWS and local authorities.
