It is expected that an atmospheric river phenomenon known as the Pineapple Express would carry Washington and Oregon a prolonged duration of rainy weather and the potential for avalanches.
Early this week, the impact of rain and substantial mountain snow will be felt.
Flooding is likely even from the few inches of rain that the storm is predicted to produce with the ground already saturated from previous storms.
Avalanche warnings have been given ahead of this heavy snow for most of the Cascades around Washington.
The Northwest Avalanche Centre has given a “high” avalanche danger warning (level four out of five) for Sunday.
Also at lower elevations, large natural avalanches are likely.
According to the Colorado Avalanche Information Center,avalanches have killed 30 individuals across the United States this winter season.
“This will mark the beginning of a wet period across Western Washington, as the southern periphery of the Atmospheric River will affect the region before it shifts southward over the area Monday,” warned the Seattle National Weather Service Office on Saturday.
For parts of Washington and Oregon, this could be another notable weather occurrence, with localised urban and river flooding along with gusty winds that could lead to power outages in both states.
During February, Seattle averages 88mm of rain, but this year the city has already seen more than a foot of rain, a surplus of 101mm.
As Oregon still has 30,000 customers without electricity from a storm last week, this new system is arriving.