Severe Storms Possible Along OR/CA Coasts
The Pacific Northwest will get locked into a wet and windy pattern this week, as a series of storms push onshore.
This map indicates how strong the atmospheric river will be for a given location. Blue and green indicate lighter impacts, while orange and red indicate stronger impacts.
(Scripps Institute of Oceanography at UC San Diego)
(MORE: What is an atmospheric river?)
We will break down the timing and impacts here:
Timing: rain, snow and wind
Two waves of rain, snow and wind will push inland from the Pacific and through the Northwest and Northern California.
Here’s a look at where the rain and snow are occurring now:
Current Radar
(This map shows where rain and snow is currently falling.)
Here’s an overview of when we’ll see each storm:
Though Early Thursday (Storm #1): The strongest of the events is working its way onshore now. This will be considered a significant atmospheric river for portions of Northern California.
Wind will be an issue with this first storm. Winds could gust at least 45 miles per hour or more in the lower elevations from northern California to the Intermountain West.
In the higher elevations from far Northern California to southern Oregon, we could see winds as high as 60-75 mph, especially in areas in dark purple on the map below. This could be enough to uproot trees and cause power outages. At the crest of the Sierra, winds could gust over 100 mph.
These winds will calm down Wednesday night.
Wind Alerts
(Areas in high wind warnings can expect difficult travel, power outages and property damage while those in a wind advisory can expect strong winds and minor damage. )
Thursday: A slight break will come between the two events, but lighter rain will remain possible in western portions of Washington and Oregon while lighter snow showers are possible in the northern Rockies.
Thursday night – Friday (Storm #2): A less strong storm system with another atmospheric river will arrive late Thursday afternoon for Washington, Oregon, Idaho and western Montana. This will bring gusty winds, rainfall well into the higher elevations and highest-elevation snow in the northern Cascades and far northern Rockies. This storm will have fewer impacts in California.
How much rain and snow?
As waves of rain push onshore this week, the rainfall totals will be stacking up. Heavy rain, mountain snow and potential mudslides will be a threat, especially in burn scar areas.
From northern California to northern Washington, widespread rainfall totals will range from 3 to 7 inches. However, there will be isolated areas that could pick up as much as a foot of rain.
There will be a threat for flash flooding, as relentless rain pushes in. The flooding potential will increase as the week pushes on, as new rain falls on already saturated ground.
The Snoqualmie River in Washington is already running high because of an atmospheric river that impacted the region over the weekend.
This should be interpreted as a broad outlook of where the heaviest rain may fall. Higher amounts may occur where bands or clusters of thunderstorms stall for over a period of a few hours.
While heavy rain falls in the lower elevations, temperatures are cold enough for mountain snow in the higher elevations.
Parts of the Cascades and northern Rockies could pick up as much as 12-18 inches of snow. Some areas could see even higher amounts.
Even parts of the Sierra Nevada will pick up some snow, albeit not quite as widespread as the northern mountain ranges, and at much higher elevations.
Snowfall Forecast
(While it is too far out in time to specify exact forecast snowfall totals, areas in the purple and pink contours have the highest chance at heavy snowfall.)
Make sure to check back often, as the forecast could change.
Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world’s biggest weather and climate stories for the last two decades.
