Atmospheric river forecast: California, Oregon and Washington face storm risk next week

Three US states are said to be at significant risk of power outages next week, as an atmospheric river is predicted to bring heavy rain, mountain snow and strong winds to the West Coast.

It comes after the NOAA Climate Prediction Center issued a warning for heavy rainfall next week, as vulnerable areas prepare for potential flooding.

Heavy snow and high winds mean that the coasts of Washington, Oregon and much of California are at higher risk of extreme weather causing disruptions such as power outages.

Three US states could see significant disruption (Getty Stock)

What is an atmospheric river?

Despite sounding like something out of a science fiction film, an atmospheric river is actually a weather phenomenon responsible for transporting huge quantities of moisture through the atmosphere.

These relatively narrow corridors of concentrated water vapour can stretch for thousands of miles, carrying moisture from tropical and subtropical regions towards higher latitudes.

When they reach land, that moisture can fall as heavy rain or snow, sometimes producing significant precipitation over a relatively short period.

Although atmospheric rivers are an important part of the natural water cycle, particularly strong systems can cause serious problems for communities in their path.

Heavy rainfall can overwhelm drainage systems and increase pressure on rivers, while strong winds can bring down trees and damage power infrastructure. In mountainous areas, meanwhile, heavy snowfall can create dangerous driving conditions and disrupt travel.

Coastal areas are at risk of flooding (Getty Stock)

Which states could be affected?

Three US states have been highlighted as being under particular threat of potential hazards, however the risk within these states will massively vary depending on location and elevation.

California

Northern and central California are among the areas facing an increased likelihood of heavy rain between next week, between November 13 and 15.

Communities in spots already known to be vulnerable to flooding will need to be on high alert, particularly if rainfall becomes concentrated over a short period.

The Sierra Nevada mountains are also included in NOAA's moderate-risk area for heavy snowfall at higher elevations.

Oregon

Oregon is also included in the Pacific Northwest's moderate-risk area for heavy rainfall. The Klamath Mountains are among the higher areas facing a risk of significant snowfall, while coastal parts of the state could experience strong winds.

These winds may bring down trees and damage power lines, potentially leaving some households without electricity.

The El Niño could play a significant role in extreme weather (Getty Stock)

Washington

Washington is another state being monitored for potentially disruptive weather, with coastal areas included in NOAA's moderate-risk outlook for high winds.

Heavy rainfall is also possible across parts of the state, although the latest forecast suggests the volume of rain could be lower than previously anticipated.

The combination of wet weather and strong coastal winds could still cause disruption, particularly for communities exposed to severe weather.

El Niño could influence the winter ahead

The developing weather system comes as a strengthening El Niño is expected to play a significant role in the US winter weather outlook.

El Niño is a climate pattern involving warmer-than-average sea surface temperatures in the central and eastern tropical Pacific. It can influence atmospheric circulation and shift typical weather patterns across different parts of the country.

While El Niño provides important context for the wider winter pattern, there is no confirmation that it is directly responsible for this particular atmospheric river.