Major Air Quality Threat For Puget Sound Sound and Western Washington

There is the potential for a major degradation of air quality over Puget Sound, a threat serious enough that vulnerable folks should be prepared.

Specifically, it is looking increasingly likely that some of the dense smoke produced by the fires in western Oregon will move northward and northeastward into western Washington, producing a profound degradation of air quality.

Potentially as bad or worse than we experienced in 2017 and 2018. 

The visible satellite image for today (top, 10:31 AM) and yesterday afternoon (bottom, 5:01 PM) shows the story.  There is a dense plume of wildfire smoke over northwest Oregon from the massive fires, and that plume of smoke is slowly moving northward.

Here in Puget Sound, we have been "protected" by the easterly (from the east) flow crossing the mountains, leaving us with the modest smoke remnants from eastern Washington.

But this is going to change in a major way as the weather pattern shifts and southerly flow develops over western Oregon and Washington.   Such southerly flow will bring smoke northward into western Washington. 

Let me illustrate our problem by the forecast winds at 2000 ft.   This plots show wind speed (color coded in knots) and wind speed/direction barbs (if you want a tutorial on how to read them, go here). 

Here are the winds at 8 AM this morning:  mostly from the east and thus protective of western Washington.

But tomorrow, everything changes with the winds switching so that they are from the south and southwest.  Very bad.  Would Oregon move smoke into Puget Sound.

And there is another major surge of southerly flow on Sunday. 

We can view the implications of the wind shift by looking at the forecasts of the wonderful NOAA/NWS HRRR smoke modeling system.  I will start by showing you predictions of near-surface smoke (purple is the worst, followed by red and orange).

At 5 PM today, only modest smoke over Puget Sound, but terrible over western Oregon.  A spur of smoke is moving into southwest Washington.

 But by 8 AM Saturday morning, substantial smoke has moved into western Washington, and very dense smoke has extended over Portland.

Sunday is a day when things may potentially get even worse for Puget Sound. An east-west vertical cross section of the smoke at 5 AM Sunday shows the worst smoke moving northward over Puget Sound (the low area between the Olympics and Cascades in the cross section).    If that mixes down, the conditions will get very unpleasant.

 The bottom line is that Portland and Puget Sound residents should be ready for unhealthy to hazardous air quality conditions.  My colleagues in the Washington State Department of Ecology have just put out a smoke alert on their excellent web site (https://wasmoke.blogspot.com/).  And I just got an email from  Eric Saganic of the Puget Sound Clean Air Agency and they are working on messaging of this potential serious event as well.

To protect yourself, there are many things you can do.  If your home or apartment has forced air with a decent air filter, stay inside with the system running.  Fortunately, temperatures will cool into the  70s over the weekend.  Buy a good air filter and tape it to a box fan...that really helps.  Purchase a commercial air filter system (some are as low as $ 50-100).   If you can get an N95 mask, use it (but they are difficult to secure because of COVID).  Most COVID-19 masks (e.g., cotton masks) are not effective for wood smoke particles.  Don't exercise during bad smoke periods.  Finally, you can check the current air quality by going here.

My podcast tomorrow will delve in depth on the smoke situation.


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from Cliff Mass Weather Blog https://cliffmass.blogspot.com/2020/09/major-air-quality-threat-for-puget.html