Back-to-Back Atmospheric Rivers Are About to Dump Huge Amounts of Rain and Snow On the West

Image: NWS Seattle/NASA
Image: NWS Seattle/NASA

It’s been a few days without a major weather event, which in 2017, feels like forever. But it appears that the next week will make up for lost time.

A series of so-called ‘atmospheric rivers’ currently stretch across the Pacific and will bring major rain, snow and winds the Northwest for the latter half of this week and early into the next. A few welcome drops of moisture could find their way into wildfire-ravaged California, too.

On Tuesday, NASA satellites captured a continuous band of clouds roughly 5,000 miles long stretching from the western Pacific straight to Seattle. This band of supercharged storms contains two atmospheric rivers, which tap moisture from the Pacific, and send it racing along the jet stream.

The first atmospheric river to hit the Northwest this winter reached the region on Tuesday. Image: CIMSS

Atmospheric rivers are responsible for up to half of the rain and snow that falls during the West’s wet season, which lasts from fall to spring. They also cause 80% of major floods that hit the West Coast.

This is the first atmospheric river event of wet season for the West. And it’s going to be a fairly major one, owing to the fact that it’s a two-for-one event.

The first river rolled ashore in the Northwest on late on Tuesday. Wind gusts topped out at 98 mph on Mt. Rainier in Washington before ice froze over the weather station.


Winds will continue to ramp up on Wednesday, with high wind warnings and watches along the Washington coast and across the Seattle metro area. Fierce winds have already knocked power out as of Wednesday morning local time in parts of the San Juan Islands in Puget Sound.


The second atmospheric river will descend on the region this weekend, bringing more of the same wet and windy weather.

Snow levels will slowly drop over the coming days from 10,000 feet to 5,000 feet throughout the Cascades in Oregon, Washington, and British Columbia. Mt. Baker ski area, located about 100 miles north of Seattle, could see up to 9 feet of snow by Friday. Other resorts could also post snow totals measured in feet, leading to early openings and prime early season backcountry conditions.


Some of the cool, wet conditions could even dip in Northern California. While the storms won’t be major rain makers for that region, every bit of water helps after some of the worst wildfires in California’s history devastated wine country. The reprieve for California could be brief, though, with hot, dry conditions in the forecast by the middle of next week.

Back-to-back atmospheric rivers aren’t rare per se, but a few things make this event standout. For one, the awe-inspiring satellite image of clouds forming an unbroken path across the Pacific is a reminder of how weather connects our planet. On a more nuts and bolts level, the intensity of this series of storms is also rare this early in the West’s wet season.


In addition to the cool, wet weather helping quell Northern California’s fires, the mountain snow in the Northwest will also help build a good base for this winter’s snowpack to cling to, which could in turn help it stick around longer in the summer.

Scientists are intensely studying how climate change could affect atmospheric rivers since they’re such an important source of precipitation for the West Coast.


A warmer atmosphere is able to hold more water, and scientists project that atmospheric rivers will be juicier when they roll ashore in the future, according to research published last year in Geophysical Research Letters. While more precipitation is likely to fall as a result, rising temperatures on land mean more of it will fall as rain rather than snow.

Managing editor, Earther

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