Atmospheric Rivers to Bring Heavy Rain, Snow, and Potential Flooding to Western U.S.
A series of atmospheric rivers is poised to deliver significant precipitation and turbulent weather to the western United States this week, according to the National Weather Service (NWS).
These weather events, often referred to as “rivers in the sky,” transport moisture from the Pacific Ocean inland, bringing heavy rain, mountain snow, and possible disruptions across multiple states.
Monday: Focus on Oregon, Northern California, and the Rockies
On Monday, the heaviest precipitation is expected to target regions stretching from Oregon and northern California to central Idaho and northwest Wyoming.
Coastal rain and mountain snow are already impacting the area, with higher elevations receiving 4 to 8 inches of snow, and over a foot forecasted for Oregon’s southern Cascades.
The NWS has issued a coastal flood advisory until 10 a.m. PST Monday for parts of Washington, including San Juan, Western Whatcom, and Western Skagit counties.
Another advisory for the Central Coast Zone remains in effect until 4 p.m. PST, warning of minor coastal flooding. Residents are urged to avoid driving through flooded areas and to adhere to road closures.
Shift Northward on Tuesday
By Tuesday, the atmospheric river will shift its focus north, bringing heavier rain to coastal Washington and increased snowfall to the northern Cascades, according to the NWS.
While these systems provide much-needed precipitation for the region’s water supply, they also raise risks of localized flooding, mudslides, and hazardous travel conditions.
Atmospheric Rivers: Vital Yet Risky
Atmospheric rivers are narrow corridors of concentrated water vapor in the atmosphere, capable of transporting as much moisture as the Mississippi River. Stronger systems can carry up to 15 times that amount, according to the National Oceanic and Atmospheric Administration (NOAA).
These systems contribute about 50% of the West Coast’s annual water supply and have ended three-quarters of the region’s droughts between 1950 and 2010, the U.S. Department of Energy reports. Earlier studies revealed 51 atmospheric river systems impacted the West Coast between October 2023 and March 2024.
Safety Warnings and Future Outlook
The NWS has urged residents to prepare for hazardous travel, avoid flood-prone areas, and stay informed through official updates. Coastal flooding may coincide with high tides Monday morning, potentially inundating roads and parking lots.
Forecasters from AccuWeather predict a brief break in the pattern midweek, with another round of storms expected to resume into the weekend and early next week.
Recent atmospheric rivers have already brought extreme weather to California, including a rare tornado warning in the Bay Area over the weekend. In Scotts Valley, suspected tornado activity overturned vehicles and recorded wind gusts of up to 83 mph.
While this week’s systems may be less impactful than earlier storms, meteorologists warn that the rainy season has officially begun. Residents are advised to remain vigilant, avoid barricaded roads, and heed local warnings.