West Coast Storm Warning for 3 States Mapped As Gale-Force Winds Forecast

Huge swaths of the Oregon and Washington coast have been issued with a Storm Warning as a blustery atmospheric river approaches the Pacific Northwest.

Parts of the remaining Washington coast, as well as the northern California coast, are under a Gale Warning, while the rest of the California coast has been issued a Small Craft Advisory and a Hazardous Seas Warning.

Gale warnings are also issued for further out in the ocean off the coast of Washington, Oregon, and Southern California.

“An atmospheric river will bring heavy, low elevation rain and high elevation mountain snow to the Pacific Northwest and northern California beginning Tuesday evening,” the National Weather Service said in a short-range public discussion.

An atmospheric river is a long, narrow band of concentrated moisture in the atmosphere that transports vast amounts of water vapor, often originating from tropical or subtropical regions. These “rivers in the sky” can carry as much water as some of the world’s largest rivers on the ground, and when they make landfall, they can release this moisture as heavy rain or snow, especially over mountainous regions.

A Storm Warning means winds of 48 to 63 knots—55 to 72 mph—are either currently occurring or are about to, while a Gale Warning means that winds of 34 knots to 47 knots—39 to 54mph—are occurring.

On the Beaufort Wind Scale, 39-46 mph winds are classified as gale-force, with winds between 47-54 mph considered a strong gale, and 55-63 mph considered storm-force. Winds between 64-72 mph are classified as a violent storm, and 73 mph winds or over are hurricane-force.

Small Craft Advisory is in place on the West Coast when “sustained winds of 21 to 33 knots (24-38 mph), and/or wave heights exceeding 10 feet (or wave steepness values exceeding local thresholds),” while a Hazardous Seas Warning is issued when “a warning for wave heights and/or wave steepness values meeting or exceeding locally defined warning criteria.”

Hazardous Sea Warnings will graduate to Storm Warnings off much of the Oregon coast on Tuesday evening when waves of up to 24 feet and wind gusts of 63 mph are forecast.

“Very strong winds will cause hazardous seas which could capsize or damage vessels and reduce visibility,” the National Weather Service Portland warned.

“Recreational boaters should remain in port, or take shelter until winds and waves subside. Commercial vessels should prepare for very strong winds and dangerous sea conditions, and consider remaining in port or taking shelter in port until winds and waves subside.”

In the Gale Warning areas, waves of up to 21-foot seas are forecast off the California coast, with 23-foot seas anticipated off the Oregon and Washington coasts.

“Seas given as significant wave height, which is the average height of the highest 1/3 of the waves. Individual waves may be more than twice the significant wave height,” the NWS Ocean Prediction Center said.

Under the Hazardous Sea Warning, areas off the Oregon coast, “very steep and hazardous seas 17 to 22 ft at 16 seconds and southwest winds 20 to 25 kt [23-29 mph],” are forecast, while under the Small Craft Advisory areas, “strong winds will cause hazardous seas which could capsize or damage vessels and reduce visibility.”

The atmospheric river system will move inland after whipping up the seas, bringing windy and rainy weather.

“[The] Atmospheric River will approach the West, bringing a wave of Pacific moisture and triggering increasingly heavier lower elevation/coastal rain and higher elevation mountain snow. The system will move inland bringing an expanding area of lower elevation/coastal rain and high elevation mountain snow to northern California and a wintry mix into the northern Rockies and Great Basin through Wednesday,” the NWS said.

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