Next Atmospheric River Ahead for the Pacific Northwest

FastCast—Monday, Jan. 10 to Wednesday, Jan. 12:

After a beautiful day on Sunday, with sunny skies and highs in the upper 40s to low 50s, the next atmospheric river is ahead. (An update on the mountain passes is below). The next atmospheric river will arrive late Monday to Tuesday. It isn’t completely certain where the most precipitation from the atmospheric river will be focused, but it is likely that Vancouver Island and the Western Olympic Peninsula will get significant rain. The Cascades will also pick up significant rain, with snow levels of 5,000-7,500 feet. Expect 1-2 inches of rain in the lowlands, 2-5 inches on the coast, and 3-7 inches in the mountains, most in the Olympics. Regarding river flooding, check back, because the outlook largely depends on where the atmospheric river sets up. Temperatures will drop to the low-mid 30s on Monday morning, then rise steadily to the mid 40s on Monday, then to the low to mid 50s on Tuesday and Wednesday. Stay tuned for more details about this atmospheric river!

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Continue reading the full blog below!

Mountain Pass Update: Snoqualmie and Blewett are open as of Sunday evening! White will remain closed through at least Monday evening. Stevens has been impacted by power outages, over 200 snow slides (some 70 feet high), and 4 inch thick ice on the road. It will not open before Wednesday.

More information: Snoqualmie Pass Twitter and WSDOT Twitter

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After a beautiful Sunday and a dry weekend, another atmospheric river is heading for the Pacific Northwest. 

Below is the UW WRF model showing water vapor in the atmosphere on Tuesday evening.

You can see a “Pineapple Express” plume of moisture extending from the subtropical Pacific Ocean into the Northwest.

How much rain is expected? Let’s take a look at the Euro and GFS (American) forecast models.

The Euro is below, with precipitation through early Thursday morning.

The Euro shows the bulk of the precipitation (10+ inches) in the Olympics and on Western Vancouver Island. This is a hazardous amount of rainfall for these areas. The lowlands will receive 1-2 inches, with more north of Everett (2-3 inches).

The GFS is similar, but with less mountain rain.

It also shows 1-2 inches in the lowlands, with a more prominent rain shadow northeast of the Olympics. The Olympics and Vancouver Island still get the most rain (5-10”).

This will be a warmer system, due to the subtropical component of this atmospheric river. Expect lowland highs in the low to mid 50s on Tuesday and Wednesday. 

Additionally, snow levels will rise above the passes and will generally be in the 5,000 to 7,500 foot range. Some snowmelt is expected, meaning that rivers draining the Cascades and Olympics could flood. 

Stay tuned for more information about this system!