The flood forecasts come as a strong atmospheric river pummels the Pacific Northwest. The storm follows a weaker system that inundated the area over the weekend. Atmospheric rivers are a "long, narrow region in the atmosphere—like rivers in the sky—that transport most of the water vapor outside of the tropics," according to NOAA.

A potent atmospheric river will unload several days of heavy rain across the Pacific Northwest starting Monday, raising

A powerful atmospheric river has triggered historic flooding across western Washington, forcing evacuations as the Skagit River nears record-shattering levels and communities brace for widespread damage.

Landslides and high water are impacting highways and roads around the county and region Monday night, Dec. 8, as a powerful AR4 atmospheric river begins a multi-day onslaught on the Pacific Northwest.

Some rivers may break records. Already, overnight into Tuesday, the Naselle River near Naselle, Washington, has gone from its normal 5 foot depth to nearly 20 feet deep, growing by 10 feet in 12 hours and coming within less than 1 foot of the historical record.

Heavy rain​ has triggered flooding, rescues and road closures in Washington state, with Gov. Bob Ferguson declaring a statewide emergency​.