Relief Ahead After One of the Smokiest Days in Seattle History

17th Century English theologian Thomas Fuller said, “It is always darkest before the dawn,” and that seems to be the case with the smoke situation in Western Washington. While relief is on the horizon, Wednesday brought one of the smokiest days in Seattle history, with AQI that was the worst in the entire world.

The air quality maps from Purple Air (link on right side of blog) as of 8:45 PM Wednesday show horrible AQI around the region.

The amount of areas with AQI of 200+ in Washington is staggering. This is in the “very unhealthy” to “hazardous” categories, meaning that the air is very unhealthy for all people. 

Zooming in on Seattle, you can see the horrible air quality measurements around the city and its suburbs.

On the Seattle side of Puget Sound, there are no measurements under 180. This means that AQI in all of Seattle and its suburbs is unhealthy to hazardous.

Seattle’s air quality is the worst among all major cities in the entire world, far outpacing the pollution hotspots of Delhi and Beijing. The table below is from IQAir and is constantly updated.

Notice that Portland has AQI comparable to Delhi, Dubai, and Beijing, cities known for pollution. It is staggering how much worse Seattle’s AQI is than those cities. I think we all can agree that it is NOT fun living in the city with the worst air quality in the world.

So…why is so incredibly smoky? The short answer is an inversion, trapping smoke in the low levels of the atmosphere. However, the inversion needed some help to make AQI this bad. The proximity of the Loch Katrine and Bolt Creek Fires to the Puget Sound area is what has caused the horrible AQI. The InciWeb map below shows the Bolt Creek (larger fire) and Loch Katrine Fires. Notice that both fires are nearly due east of Seattle.

As Cliff Mass explains, today was Seattle’s worst air quality since September 2020. His blog explains how the local fires spewed smoke under the inversion to produce horrible air quality, with far smaller fires than in 2020. Read it below:

Cliff Mass Weather Blog: How Could Air Quality in Western Washington Be So Bad When the Wildfires are Third Rate?

There is good news…relief is coming!

Let’s start with the HRRR smoke forecast for 8 AM Thursday.

Surface smoke will still be heavy in places, and AQI will still be degraded, but it will be an improvement from Wednesday.

By 4 PM Thursday, onshore flow has clearly kicked in.

Notice that at 4 PM, smoke has not fully cleared from Western Washington. This is due to the inversion, which will delay the full exit of surface smoke until very late Thursday, when winds can finally mix out the inversion with cleaner air. Onshore flow Thursday afternoon will create large plumes of smoke that will push into Eastern Washington, bringing areas of unhealthy to hazardous AQI.

By 8 AM Friday, conditions are back to normal for Western Washington!

However, Friday will bring more areas of surface smoke for Eastern Washington, particularly on the eastern slopes of the Cascades and in the Spokane/Davenport area.

By 5 PM Friday, smoke plumes will be present again.

By Friday afternoon, continued onshore flow will bring more smoke plumes to Eastern Washington, degrading air quality downwind of fires.

However, expect conditions to improve even more over the weekend, with the near complete end of smoke plumes. This is due to the upcoming rain and mountain snow. 

Below is the European model forecast for rain through 5 AM Sunday.

Expect 0.5-1” in the lowlands and 1-1.5 inches in the Cascades! This will significantly impact area wildfires, and will also bring a chance of debris flows off burn scars if rain is heavy enough.

Additionally, temperatures will cool enough that snow could fall on some wildfires. The European model forecast for snow through 5 AM Sunday is below.

Areas above 4,000 feet will receive 1-4 inches of snow, with even higher elevations picking up 6-10 inches! 

In short, less than 48 hours after one of the smokiest days in Seattle history, rain will fall in the lowlands and Cascades, with higher elevations getting snow. It will be a relatively quick transition from dangerous air quality to a fall storm. Stay tuned!