Large Weather Swing Ahead

 FastCast—Friday, Jan. 27 to Tuesday, Jan. 31:

After a very persistent high pressure ridge kept clouds and calm conditions in place most of the week, a change is ahead. Rain is expected at times through late Saturday, most from Seattle northward to Skagit County. For those areas, expect 0.4-1 inch of rain. Outside those areas, expect 0.1-0.3 inches. Snow will fall in the mountains as well, most from Thursday night to midday Friday and then on Saturday. At the passes, expect totals of 8-12 inches, with some impacts possible. Conditions will rapidly clear and dry out late Saturday night into Sunday morning, with temperatures dropping from the low 40s to the upper 20s. Brisk northeasterly winds will bring wind chills in the teens on Sunday and Monday. Monday morning’s lows will be in the upper teens to low 20s across the lowlands, before temperatures begin warming back up, with lows in the upper 20s to low 30s on Tuesday morning. Overall, expect highs in the mid to upper 40s on Thursday and Friday, with lows in the upper 30s to low 40s. Saturday is the transition, with highs in the low to mid 40s changing to lows in the upper 20s by Sunday morning. On Sunday and Monday, expect mostly sunny conditions with highs in the mid to upper 30s and lows in the upper teens to low 20s. 

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Continue reading the full blog below!

After a very persistent high pressure ridge dominated weather this week, a significant swing is ahead over the coming days.

This will start with a couple weak systems bringing rain and mountain snow through Saturday night, before high pressure builds east of the Rockies, pushing frigid air into the Pacific Northwest. 

Below is the European model forecast for rain through Saturday night.

Expect 0.4-1 inch from Seattle northward to Skagit County. From Seattle southward and on the coast, expect 0.1-0.4 inches. This odd distribution of precipitation is due to the weak nature of these systems and the northwesterly angle they’re arriving from.

Next, take a look at the European model forecast for total snow through Saturday night.

Expect 8-12 inches in the passes through Saturday night, with 1-3 inches for Spokane and 0.2-1 inch for Wenatchee and Yakima. Travel impacts are possible in the passes, with the most snow expected from late Thursday to midday Friday and on Saturday.

Then, on Saturday night, a big change occurs. Surface high pressure will build east of the Rockies, ushering in arctic air to the Pacific Northwest. Below is the European model upper-air map for late Saturday.

Notice the green arrows, showing the arctic air moving in from the interior of Canada. This means that it is very dry, ending any chance of lowland snow this weekend.

How cold will it get? There will be a significant decrease in temperatures from Saturday morning to Sunday morning, as seen in the European model forecast below.

This forecast shows that temperatures at 7 AM Sunday will be 10-20 degrees colder in Western Washington and 15-25 degrees colder in Eastern Washington than they were at 7 AM Saturday.

As of now, the coldest temperatures are expected to be on Monday morning. The European model forecast below shows Monday morning’s lows.

Expect very cold temperatures in the upper teens to low 20s for the lowlands, except in the mid 20s near the water. Eastern Washington will be even colder, with lows of zero to the mid teens expected. 

I will have another update on the cold by Saturday evening. Stay tuned!