FastCast—Wednesday, Jan. 25 to Monday, Jan. 30:
A very strong high pressure ridge is dominating weather for the Pacific Northwest, and it is expected to continue influencing our weather for the next few days. The highest pressure in recent years (30.68-30.75”) will impact the region on Wednesday. Expect overcast conditions through Saturday. Weak systems sliding across the northern boundary of the ridge will bring 0.2-0.5 inches of rain through Saturday night, except 0.75-1.25 inches from Seattle northward. Highs will be in the mid to upper 40s, with lows in the upper 30s to low 40s. A significant change is expected on Sunday. The ridge will retrograde north to Alaska, opening up a cold air conduit for Arctic air to enter the Northwest. Conditions will clear up and temperatures will be noticeably colder. Brisk northeasterly winds will bring cold wind chills, and the air will be much drier. From Sunday to Monday, expect mostly sunny conditions with highs in the mid 30s to around 40º, and frigid lows in the low to mid 20s for the lowlands, and potentially in the upper teens for the foothills and outlying areas. Eastern Washington will likely drop into the 5 below to 10 above range. Stay tuned for updates over the next few days.
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A large ridge of high pressure is dominating weather across the Pacific Northwest, bringing the highest atmospheric pressure in years (which will negate king tides). Below is the European model forecast showing the ridge (green box) late Wednesday.
The ridge will dominate weather at upper and lower levels of the atmosphere (it’s smaller at lower levels). However, since Western Washington is on the northern edge of the lower-level ridge, some weak systems will make their way over the ridge and bring showers to the region from Thursday to Saturday.
Below is the European model, showing rain through Saturday night.
Expect the most rain (0.75-1.25 inches) from Seattle northward, as the angle of these systems causes rain shadowing over the South/Central Sound. For areas from Seattle southward, expect 0.2-0.5 inches of rain. The coast will pick up 0.3-0.5 inches.
These weak systems will bring snow to the mountains, especially on Friday. Below is the European model forecast for total snow through Saturday night.
Delays will be possible if you’re crossing the mountain passes. Expect 6-10 inches at the passes through Saturday. Additionally, areas from Ritzville eastward in Eastern WA will pick up 1-4 inches of snow.
From late Saturday into Sunday, a big change will take place. Below is the European model upper-air forecast for late Saturday.
Notice that the ridge has gotten much larger and moved away from the Pacific Northwest. Its new position allows arctic air to enter into the region, as seen in the dark blue/purple colors (a trough, opposite of a ridge) that are over our region.
This will bring significantly colder temperatures, especially in the mornings. The European model forecast for Monday morning’s lows is below.
The European model shows very cold temperatures for the entire region. The entirety of Western Washington has a good possibility of dropping into the upper teens to low 20s, with brutally cold temperatures in the 5 below to 10 above range for Eastern Washington and the Cascades.
This overall pattern change can be seen in the NWS Climate Prediction Center outlook for temperatures from January 30th to February 3rd.
Wow. This outlook shows a 70-90% probability of below average temperatures for January 30th-February 3rd. Percentages this high usually indicate that it’s fairly certain that we will have cold temperatures.
Stay tuned for more information as this cold pattern continues to evolve. Next blog on Thursday night!
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