Weak Atmospheric River Fueling a Rainy Week

FastCast—Sunday, Mar. 13 to Tuesday, Mar. 15:

After a warm day on Saturday (highs in the upper 50s), a rainy few days are in store for most of Washington state. A storm will approach the Oregon Coast on Sunday, bringing gusty winds there (50-60 mph) and some showers to Western Washington. On Monday, a weak atmospheric river will impact the region, bringing 0.5-1.5 inches of rain, mainly south of Seattle. Areas from Seattle northward will have 0.1-0.75 inches of rain, generally in the rain shadow. The mountains, foothills, and coast will receive 1.5 to 5 inches of rain. Snow levels will hover between 3,000 and 4,500 feet, likely bringing a mix of rain, wintry mix, and wet snow to Stevens and White Passes, and rain at Snoqualmie Pass. Expect up to 6-12 inches of snow at the higher passes. Temperatures will be steady, with highs in the upper 40s to low 50s, and lows in the 40s.

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Daylight Saving Time begins at 2 AM PDT on Sunday, March 13th. Don’t forget to “spring forward!”

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Continue reading the full blog below!

It’s going to be a wet week in Western Washington. We are in the path of multiple storm systems (not any significant ones) that will bring some rain each day for the next few days. Below is the European model forecast for rain through Wednesday morning.

Through Wednesday, expect 0.75 to 1.75 inches of rain around the lowlands. The coast, foothills, and mountains will receive 2-4 inches, potentially more. Eastern Washington will also receive 0.4-1 inch, much-needed rainfall for the region.

Most of this rain will fall on Monday (0.75-1.25” in the lowlands) due to a weak atmospheric river that will bring more moisture to Western Washington. The UW forecast below for Monday evening, showing moisture in the atmosphere.

The Oregon Coast and Willamette Valley will receive the brunt of the impacts from this atmospheric river, with 2-4 inches of rain on the coast and 1.5-2.5 inland.

The Oregon Coast will also be the epicenter of a small windstorm on Sunday. A compact and weakening low center will make landfall around 7 AM Sunday on the Northern Oregon Coast, as seen below in the UW forecast.

The area outlined in red will receive the strongest winds, due to a higher pressure gradient (close black lines). Expect winds gusting up to 60 mph through Sunday afternoon, particularly from Tillamook to Coos Bay. On the Southern Oregon Coast, expect waves of up to 20-30 feet!