Atmospheric river to continue flowing over Pacific Northwest early in the week

The Pacific Northwest got a respite from heavy precipitation to begin the weekend. However, AccuWeather forecasters say that another atmospheric river will bring a renewed threat of flooding.

Even though much of the West is still in a drought according to the United States Drought Monitor, the recent train of storms has eliminated the drought in northwestern Washington and far northwestern Oregon. Even with the drought gone, other issues have arisen.

"Many area rivers are running near bankful already from the recent stormy pattern, so the risk of flooding will increase rapidly throughout the day on Monday as the storm moves inland," cautioned Buckingham.

Cities such as Astoria, Oregon, and Seattle are likely to receive 2-4 inches of rain total. On the Puget Sound to the west of Seattle, locations such as Quillayute, Washington, could have 4-8 inches of rain.

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Buckingham also noted that rain may fall heavily enough for landslides to also be a concern in rugged terrain and any areas burned by this past summer's wildfires. In some areas of southern British Columbia, Canada, mudslides and heavy rain buried and flushed multiple vehicles off highways as residents sheltered in recreation centers. The nearby county of Whatcom, Washington, declared a state of emergency due to these threats. A team of 35 first responders commenced rescue operations for up to 10 people trapped in their vehicles early Monday morning.

In addition to the rain and flooding potential, winds also increased throughout the day on Sunday. The precipitation and strong winds will continue into Monday night, but changes will also be taking place.

Not only will there be a risk for flooding, but snow levels will fall rapidly into Monday night, quickly falling below most major pass levels across the Cascades.

This will be due to a cold front moving ashore. Given the very warm air preceding the front, the drop in snow levels will be faster than what is typical in the Pacific Northwest. Therefore, even motorists used to traversing the region in winter weather may be caught off guard.

"On top of the falling snow, making for difficult driving, the rapid drop in temperatures can lead to a quick freeze-up of any standing water on the roads as well," warned Buckingham.

Rain and snow will also work farther to the south into Monday evening, with a brief period of heavy rain along the coast of Oregon and heavy snow in the Cascades of Oregon. Since precipitation will not fall for nearly as long as farther north, impacts will be minimal but minor flooding is possible and travel will be treacherous in the higher elevations with snow-covered roads likely.

Precipitation will rapidly taper off late Monday night, although some snow may linger in the Washington Cascades. However, that will not be the end of the storm. While some snow will fall, the main issue will become wind and the wind is likely to be stronger than what it will be in the coastal Northwest.

"The storm will continue to march inland early this upcoming week, likely bringing along dangerously strong wind gusts to eastern Washington, northern Idaho and across Montana and travel can become extremely difficult, especially for high-profile vehicles across typical wind-prone areas," stated Buckingham.

A precipitation-free and less windy day is expected on Wednesday. Another system is forecast to come ashore by Thursday. This time, the focus will be across Oregon and Northern California and precipitation amounts are not expected to be excessive. This system will largely fall apart on Friday before it crosses the Rockies.

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