Atmospheric river soaks Pacific Northwest again this weekend with heavy rain, mountain snow

Heavy rain returned to the region this weekend, adding more water to swollen rivers that have mostly returned to their banks after reaching moderate to even record flood levels last week but are still running high.

SEATTLE – An atmospheric river is dumping another round of heavy rain and mountain snow across the Pacific Northwest, which is still dealing with swollen rivers and saturated grounds from a deadly rainstorm last week.


The storm began drenching the region Saturday morning. It promised a solid 24-30 hours of steady rain that would continue into Sunday afternoon, adding more water to rivers that just returned to their banks after reaching moderate to even record flood levels last Tuesday and Wednesday and are still running high.

As much as 5 inches of additional rain could fall

This weekend's atmospheric river differs in three ways from its predecessor last week: It’s a bit weaker, it’s moving faster, and it isn’t anywhere near as warm as the record-breaking temperatures that brought snow levels as high as 10,000 feet last week. Those changes will keep snow levels lower, meaning less water will immediately reach the rivers.

A three-hour radar loop showing where rain (green) and snow (blue) are ongoing. Severe Thunderstorm Warnings are indicated in yellow. Tornado Warnings are indicated in red, while Tornado Warnings with a confirmed tornado are indicated in purple. Flash Flood Warnings are indicated in green, while Flash Flood Emergencies are indicated in pink.
(FOX Weather)


On the other hand, the return of impactful snow and then freezing rain to the mountains and their passes will present travel challenges to those heading into the passes until snow levels rise once again above pass levels on Sunday. And rainfall amounts will still be impressive. 

By Monday, about another 1-2 inches of rain is likely along the coastal regions and mountains. 

Rain forecast through Monday.
(FOX Weather)


"This is a lot of heavy rain kind of moving in and butting up against the Coastal Range and Olympic Mountains … so that’s going to add to the flood factor there," FOX Weather Meteorologist Britta Merwin said.

Wind gusts are likely to reach 45 mph along the coast and in far northwestern Washington, adding a sideways angle to the pelting rain. Wind Advisories are in effect through Sunday morning. 

The rain is coming on top of what has already been a month's worth of rain in the Northwest. 

Pacific Northwest December rainfall totals.
(FOX Weather)


So far, it appears any new flooding impacts will be minor but still bear watching. Flood Watches are in effect for the northwestern Oregon and Washington's Skokomish River. The National Weather Service warns some rivers in the central Washington Cascades may return to flood stage if the rain persists.

Flood alerts.
(FOX Weather)



Travel impacts will also return to the mountains, with winter weather alerts in effect for the eastern Washington Cascades. 

Snow changed over to freezing rain in the mountain passes by Sunday morning, with snow also pushing into Wyoming, Montana and Idaho.

Snow will spread east into parts of the inland Northwest and far northern Rockies, with moderate snow accumulations of 2-4 inches likely around Spokane, Washington, and northern Idaho through Sunday.

The long-range forecast shows a break in the weather early this week as a brief ridge of high pressure allows the region to wring out.