Friday, September 8, 2017

Last bit of smoke holding on in western WA; limited relief en route east of the Cascades

The fact that the Pacific Northwest is the smokiest part of the country should come as no surprise to most, given the # of wildfires and the not-so-cooperative weather we've been having. Here's how we stacked up nationally yesterday, with the dot colors explained in the map legend above. Grey shading indicates smoke plumes of varying density.
An aside: if you're wondering how on earth west coast smoke could impact the east coast, bear in mind that plumes have been observed to circle the globe in about two weeks.

What is that smoke still doing in western WA?
Overstaying it's welcome for sure! A few green dots have appeared on the real-time monitoring map and that trend is set to continue today as light on-shore winds persist. Reason air quality hasn't yet gone all green is because (1) on-shore winds are very light (<5 mph) so ventilation is limited, and (2) some light Oregon/ California smoke hanging aloft has likely mixed down. Balloon data from the Washington coast show the inversion is much weaker than 24 hours ago, but still present.

Here's how several representative monitors across western WA have trended in the last 2 days. Improvements through noon yesterday and then some stalling:

An all-green western WA is expected later today and will stay that way through Sunday, possibly Monday. If models have it right, Tuesday is looking ripe for some smoke along the I-5 corridor. Please stay tuned.

Will it really improve east of the Cascades?
Yes, a little. But not for long. There are fewer Hazardous/ Very Unhealthy spots on the monitoring map compared to two days ago, and we can expect a few more locations to drop a color notch or two by Saturday. Unlikely to see much Good air though.

Here's the 24-hr average fine particle pollution levels predicted by WSU's Airpact model for Saturday, showing not-so-Good air after all the Montana smoke is gone and the Cascade fires have filled the void. Concentration scale is transparent < blue < green < yellow < orange < red.

Sunday marks a return to light winds, implying smoke accumulation. Conditions are likely to worsen Monday- Wednesday for most of eastern WA and the marginal improvements today and tomorrow will be of little comfort to most but sadly that is the forecast we have to live with.

A more detailed forecast for the communities downwind of the Cascades fires will be posted separately.

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