Three US states are preparing for potentially disruptive weather as an atmospheric river is forecast to bring heavy rain, mountain snow and strong winds to the West Coast. The NOAA Climate Prediction Center has highlighted areas at risk of significant rainfall, raising concerns about flooding, dangerous travel conditions and possible power outages between November 13 and 15.

An atmospheric river is a long, narrow corridor of concentrated water vapor that transports enormous amounts of moisture through the atmosphere. When it reaches land, that moisture can fall as heavy rain or snow. These systems are a natural part of the water cycle, but particularly powerful ones can overwhelm drainage systems, raise river levels and bring down trees and power lines.

California, Oregon and Washington could all experience different impacts. Northern and central California face increased rainfall concerns, while higher elevations of the Sierra Nevada could receive heavy snow. Oregon may see significant rain, mountain snowfall and strong coastal winds. In Washington, coastal communities face potential high winds, with heavy rain also possible in some areas.

The approaching storm system comes as El Niño is expected to influence the broader US winter weather pattern. This climate phenomenon involves warmer-than-average ocean temperatures in the tropical Pacific and can affect weather conditions across the country. However, it has not been confirmed as the direct cause of this particular atmospheric river. Residents in vulnerable areas are being encouraged to follow local forecasts and prepare for possible disruptions.