Western Washington has avoided severe smog for most of the summer, but that will change tomorrow, as cloudy skies, red sun and deteriorating air quality move west of the Cascades.
Current visible satellite imagery shows a significant plume of smoke moving southeast from a fire over the North Washington Cascades (I put in an arrow indicating the plume of smoke)
Currently, eastern Washington is fuming, but later today the weather pattern will change, with flow from the east (from the east) moving into Washington State. As a result, the chimney will rotate and point southwest towards Puget Sound.
Now let me show you the smoke prediction from the NOAA HRRR smoke model.
First I will present vertically integrated smoke prediction, which is basically the summation of smoke in a vertical column of air. Smoke at the surface will be less. But this is a good measure of how a smoky sky will appear.
At 5 p.m. today, most of the smoke will be east of the Cascade Peak.
But by 4 a.m. tomorrow (Friday), smoke is billowing across Seattle and the WA central coast. Many people will wake up to a sky full of smoke.
And by 11 a.m., the obstacle will have spread to the southwest coast of WA and north of the Willamette Valley.
So hazy skies are a good thing, but what about poor surface air quality? This can be determined from the near-surface smoke predicted by the HRRR smoke model.
At 4 a.m. tomorrow morning, surface smoke will spread over the western slopes of the Cascades.
And by 2 p.m. Friday, smoke will rise over much of northwestern Oregon, central Puget Sound and southwestern Washington.
A saving grace for Seattle would be that the low-flow northward from northwest Washington would be relatively clean. Smokey air will pass through it.
Smoke will be present for most of Saturday, with low smoke levels increasing on Sunday morning (3 a.m. shown below).
If you are sensitive to smoke and fire, now is the time to prepare. All of our COVID preparations can be used to reduce exposure to secondhand smoke. If you have an air purifier, you can run it in a small room to clean the air. You can wear an N95 mask. If you have a box fan, stick a good furnace filter on it and use it in a small room.
By the end of Sunday, the smoke situation should have improved. One unknown is whether new fires will start west of the Cascades over the next two days – and that will be up to you all.