This blog post explains the approaching atmospheric river expected to strike the Pacific Northwest later this week. It summarizes forecasts from the National Weather Service (NWS) and NOAA, the areas most likely to be impacted, the primary hazards—including heavy precipitation, strong winds, significant coastal waves, flooding, and mudslides—and practical steps residents and communities should take to prepare.
I draw on decades of meteorological experience to clarify the science and suggest sensible precautions.
Overview of the forecast and what an atmospheric river means
Forecasters identify this event as the first “true” atmospheric river of the season for the Pacific Northwest. NOAA describes atmospheric rivers as narrow bands of concentrated water vapor in the atmosphere that can transport vast amounts of moisture hundreds to thousands of miles.
When these bands make landfall they can produce both beneficial snowfall at higher elevations and hazardous heavy rain at lower elevations.
Why this system matters
This system has been on the NWS Climate Prediction Center’s radar for about a week. The Weather Prediction Center’s outlook for October 23–27 highlights a corridor from Northern California through Washington state as the primary impact zone.
The combination of coastal exposure, mountainous terrain, and saturated soils in some basins increases risk potential for rapid runoff, flooding, and slope failures.
Expected impacts across the region
The forecast calls for a multi-day event with coastal and inland differences in hazards. Coastal communities should prepare for heavy waves and high winds.
Inland valleys and river basins should anticipate heavy rainfall amounts that could exceed local drainage capacities. Higher elevations are likely to receive substantial snowfall instead of rain.
This can add complexity to travel and infrastructure stresses.
Key hazard details
Forecasters are calling for the following site-specific impacts and timing:
Practical preparedness advice
As an operational forecaster for many years, I emphasize that preparation reduces risk. Residents and local officials should monitor official NWS and local alerts and take precautionary steps now rather than waiting for last-minute warnings.
Recommended actions
Consider these practical measures:
Here is the source article for this story: Map shows which states will get hit hardest by atmospheric river