Two powerful storm systems are walloping parts of the nation’s northern tier and are expected to cause serious disruptions and travel headaches through Friday.
A concentrated strip of deep atmospheric moisture, known as an atmospheric river, is blasting the Pacific Northwest with heavy rain and mountain snow. And, in the Upper Midwest, an intensifying, windy storm, sometimes referred to as a “November witch,” is unleashing pasty, wind-whipped snow in northern and western Minnesota and the eastern Dakotas.
The atmospheric river, drawing tropical Pacific moisture from as far away as Hawaii, has prompted flood watches through Friday for western Washington state and northwest Oregon. Seattle and Portland, Ore., are included in the watch, with river flooding the primary concern.
In the Upper Midwest, the November witch has prompted a blizzard warning through Friday evening for northeast South Dakota and a sliver of west-central Minnesota. Here, the combination of several inches of snow and wind gusts up to 55 mph could create whiteout conditions and extremely difficult travel.
The turbulent conditions in the Pacific Northwest and Upper Midwest are typical of weather patterns in La Niña events, which are characterized by cooling waters in the tropical Pacific Ocean. The cooling waters set off a chain reaction, which often steers storms across the northern United States during winter. What we’re seeing now is probably a sign of things to come.
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SOURCE: The Washington Post, Jason Samenow and Matthew Cappucci