First Atmospheric River of the Season Could Bring Heavy Rain to Northern California
A significant atmospheric river is poised to impact Northern California this week, marking the first such storm of the season.
The National Weather Service (NWS) has described the approaching system as “rather impressive,” with the potential to bring substantial rain and snow to the region starting Wednesday, November 20, and lasting through the weekend.
An atmospheric river carries large amounts of water vapor from the tropics, often delivering heavy rainfall and snowfall upon landfall. These storms can dramatically affect the state, as seen in October 2021, when an atmospheric river brought San Francisco 750% of its average monthly rainfall in a single event.
Meteorologists are still refining forecasts for the storm’s trajectory, but confidence is growing that Northern California, particularly far northern areas of the state and areas near the Oregon border, will bear the brunt of the impacts. Forecasts suggest the storm could range from moderate to extreme, with some experts, like UCLA climate scientist Daniel Swain, noting the possibility of a category 5 atmospheric river, the most severe on the scale.
Presently, it looks like strong (even "extreme," i.e., AR-Cat 5) #AtmosphericRiver (or two) may affect coastal OR & perhaps also parts northern CA. Confidence that strong AR will make landfall *somewhere* is high, but positional uncertainty is also high. #CAwx #ORwx [4/6] pic.twitter.com/0xVYdNao19
— Dr. Daniel Swain (@Weather_West) November 16, 2024
While the precise impacts remain uncertain, the storm could deliver much-needed relief to the Bay Area, which has only received 28% of its normal rainfall to date. Scattered showers are expected Sunday evening, followed by clearer skies on Monday before the storm system arrives midweek.
The NWS will continue to monitor the storm and provide updates on rainfall amounts and potential flood risks as the forecast becomes clearer. Residents are advised to stay informed and prepare for possible flooding in low-lying areas.
