After weeks of air quality issues throughout from wildfire smoke and high temperatures nearing 90 degrees, changes are coming. We've been seeing smoke clearing out and cooler temperatures rolling in over the last week.
Could it mean the end of summer heat? KNKX weather expert Cliff Mass says yes, especially over Labor Day weekend with high temperatures only hitting the upper 60s and low 70s.
"Saturday should be the best day, I think, with a little bit of clouds in the morning then it'll open up," Mass said.
Sunday will bring more clouds, and Mass says an upper level trough off the Pacific will move in and could mean rain for the region.
"People need to be prepared for that," he said.
Monday could still be cloudy, but might clear as the day goes on. Mass says he expects to see improvements on Tuesday and Wednesday, though the cooler temperatures will linger because of a shift in the region's weather.
"There's been a big shift in the atmospheric circulation. We had an area of high pressure, which we call a 'ridge' in the business, that was over the western United States. That high pressure was giving us warm air, offshore flow, which also brought smoke in. That pattern was locked in for a few weeks," Mass said.
Now that ridge has weakened and weak troughs are coming in with relatively cool northwesterly flow off the ocean.
"It doesn't look like anything is going to be disturbing that," Mass said. "I've looked two weeks ahead --that's as far as I have any skill--and it looks like there is no heat waves in our future."
He says the region may be through the worst in terms of heat and smoke. But, it turns out, the smoke that blanketed the area earlier in August was actually helping to keep temperatures down during the day.
"The smoke actually reflects a lot of the sun's rays back into space and it causes cooling," Mass said. "So, on the smokiest days the temperature was actually cooled by 5 to 15 degrees. It tends to prevent us from getting as warm. Then at night, we're often warmer than we could have been because of the smoke. The smoke acts as a blanket."
Mass says the Earth tends to emit infrared radiation to space at night, which leads to cooler temperatures, but the smoke slowed down that process, trapping in the heat.
Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, via iTunes or Google Play.