Fire and Smoke Update

The visible satellite image this morning shows huge contrasts over the region.  Modest smoke over the western WA lowlands, a bit denser smoke over the western side of the Columbia Basin, and dense, horrific smoke over western Oregon from a series of active fires on the western slopes of the Oregon Cascades.  Also note a lack of smoke at higher elevation over Washington (hint: you could take a nice higher-elevation hike in clean air).

The event in western Oregon is huge, involving hundreds of thousands of acres.

Current air quality (see below) is poor (red and purple) from Wenatchee to Omak, and hazardous in the Willamette Valley.

Satellite technology offers powerful tools for determining where active fires are location, based on the radiation emitted by fires.  Here is an image showing active fires (orange color) and smoke from the NOAA/NWS GOES-17 satellite.  Huge, active fires on the western slopes of the Oregon Cascades, with massive smoke plumes blowing to the west.   Importantly, there is little fire activity across Washington State. 

Most of the major fires earlier this week were mainly grass fires that burn quickly in a flashy way.  They are accessible to firefighters and generally stop when they hit some kind of obstacle (e.g., a river or irrigated agricultural land).  The fires in Oregon include forest with huge amounts of fuel and driven by the persistent easterly winds.

So what is going to happen to the fires and the smoke?   

The key issue is wind.

During the past few days, we have had unusually strong and persistent easterly (from the east) winds in the lower atmosphere over western WA/Oregon and the Cascades.   A plot of winds, temperature, and heights (think pressure) at roughy 5000 ft (850 hPa pressure level) this morning shows the situation clearly (below, click to enlarge).  Those little barbs provide the wind speed and direction.  Higher pressure/heights in eastern Washington, lower to the west.

This flow pattern is moving smoke over the mountains at low levels and will continue during the day, so expect the current air quality to continue for a while.  But northerly winds will develop this afternoon over Puget Sound, which will bring some cleaner air into Seattle later today.

I will end by showing you the predicted near-surface smoke from the NOAA HRRR model.

This morning at 11 AM, there is mega-smoke over western Oregon and modest smoke over western WA.

But things improve a bit over Puget Sound during the day and by 11 PM, the air may not be too bad over Puget Sound.

Unfortunately, overnight (8 AM Thursday shown) more (but modest) smoke is predicted to move back over Puget Sound.  Interestingly, Portland is not doing too bad with flow through the Columbia Gorge and the Oregon fire smoke staying to the south.  And yes, California is terrible as well.

On Friday, the marine air will start moving in, which should improve our air quality, if we can avoid getting hit by the Portland smoke.  More on that later.

A big question that some folks are asking is:  how much of this is due to global warming.  I will deal with that in a future blog.  But let me give you something to think about.   The big fires this week were associated with both warm/dry conditions and very strong northerly and easterly winds.  To determine whether global warming could contribute to the recent events, you have to analyze each mechanism separately.

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from Cliff Mass Weather Blog https://cliffmass.blogspot.com/2020/09/fire-and-smoke-update.html