Cooler temperatures are more likely to occur where smoke is the thickest

Posted: Sep 11, 2020 / 05:00 AM PDT

Updated: Sep 11, 2020 / 08:08 AM PDT

PORTLAND, Ore. (KOIN) — This will be a test of mental strength for everyone as a hazardous smoky blanket infiltrates the sky at least until Monday with Air Quality Alerts posted across the region.

Dense smoke will be even worse today for the western half of Oregon and Washington. According to IQAir, Portland ranked the worst for air quality across the globe due to wildfire smoke. Smoke will follow a new wind pattern moving in a northeasterly direction, spreading across the entire Pacific Northwest out past Montana.

Expect highs in the upper 70s to low 80s. Cooler temperatures are more likely to occur where smoke is the thickest.

So what’s the good news? Rain is in the extended forecast. Onshore winds will help to push the smoke away and bring moisture to this desert air mass.

Because we have large wildfires burning up and down the western half of Oregon and beyond, there’s a large supply of smoke. With the new wind direction in motion, smoke will drift to the north and east. That means eastern and central Oregon, you’re the next recipient of our hazardous plume.

What is in wildfire smoke?

Smoke is a complex mixture of carbon dioxide, water vapor, carbon monoxide, particles, hydrocarbons and other organic chemicals, nitrogen oxides, and trace minerals. Fine particles are the principal pollutant of concern from wildfire smoke for short-term exposures (hours to weeks).
Airnow.gov

A stronger onshore push could spell westerly wind gusts through the gorge tonight, gusts up to 25 mph. Again, this would be localized for the gorge not widespread like Monday’s unwelcome offshore blast.

Other things that keep smoke in place: nearly calm wind at the surface and this inversion – high pressure/sinking air. This essentially pulls smoke to the surface. It will take a trough of low pressure to give this smoke a good push out. How about some rain?

There is a chance for rain by Monday night. On a broad scale it appears an atmospheric river may be developing over the Pacific. If so, that would give us the chance to get some measurable rain next week.