Another powerful atmospheric river is set to hammer the Northwest, bringing heavy rainfall and exacerbating the already significant flood threat in the region. The storm, expected to arrive late Monday, will intensify the flood risk, with over half a foot of rain forecasted to drench the already soaked area.

Flood watches have been issued for more than 10 million people across the Northwest, covering portions of Washington, Oregon, Northern California, and Idaho through Wednesday. Northwestern Washington is particularly at risk, with a Level 3 out of 4 moderate risk of excessive rainfall in place on Monday.

Atmospheric rivers, tropical moisture systems that transport heavy rain and snow from the Pacific, are known for causing severe winter storms in the Northwest. Categorized on a five-point scale, this week's event is considered a Level 4 out of 5, or "extreme," atmospheric river for most of the Oregon coastline and a Level 3 out of 5 "strong" event for the Washington coast.

The heaviest rainfall is expected to begin on Monday evening, hitting coastal Washington and Oregon before reaching the Cascade mountains. Snow-covered elevations in the Cascades may see over a foot of rain from Monday through Wednesday. Meanwhile, western parts of Washington and Oregon could experience rainfall amounts ranging from 3 to 6 inches this week.

The recent heavy rainfall over the weekend has already saturated the ground, reducing its ability to absorb more water. The first atmospheric river brought more than 4 inches of rain to parts of Washington, Oregon, and California, contributing to a heightened flood risk. In addition, significant snowfall was recorded in the Cascades and northern Rocky Mountains, further increasing the potential for flooding as the snow melts and flows into rivers and streams.

Rivers in western Washington, such as the Skagit and Snoqualmie rivers, are projected to reach moderate and major flood stage, posing threats to roads, farms, and residential areas. Avalanche warnings have also been issued in Washington and Oregon as heavy rain combines with deep snow in the mountains. Areas previously affected by wildfires may face an increased risk of landslides or debris flows due to the ground's reduced ability to absorb the rainfall effectively.

While storm activity is expected to subside by Thursday and Friday, there are early indications from forecast computer models of yet another atmospheric river approaching the region during the upcoming weekend. The precise strength and impact of this potential event will become clearer once this week's atmospheric river concludes on Wednesday.

As the Northwest braces for another onslaught of heavy rain and a heightened flood threat, authorities advise residents to stay updated on weather conditions, heed evacuation orders if necessary, and take precautions to protect themselves and their properties from potential flooding and associated hazards.

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