Northwest Fire Update 9-9-2020

Northwest Fire Update 9-9-2020

We’re waking up to another morning of heartbreaking images coming out of Oregon as fires continue to rage, driven by offshore flow and incredibly dry conditions. This morning’s satellite image continues to show an unfathomable amount of smoke pouring out of these majors fires.

So far over 587,000 acres have burned in Washington, breaking our previous record of half of a million acres burned in 2015. There are currently no estimates on how many acres have burned in Oregon, but they will likely be breaking their record as well.

Some of the air quality readings coming out of the central and southern Willamette Valley are beyond what have seen west of the Cascades, with many stations reading well above the hazardous threshold of 300 AQI.

Air quality readings in Washington this morning are in the unhealthy range around Seattle, with hazardous air quality being reported near the Cold Springs Canyon fire near Okanogan.

Air quality will continue to be a concern across the west coast for the rest of the week thanks to a building ridge of high pressure. This ridge of high pressure will act as a cap that will trap all of this wildfire smoke in the the lowlands.

Fire danger remains incredibly high through Thursday night due to easterly winds and a ridiculously dry atmosphere. Our relative humidity has been ranging from 20-35% in Oregon and 30-50% in Washington which is incredibly dry for our maritime climate.

Thankfully the easterly winds that have been driving these major fires in Oregon will start to diminish today and into tomorrow as our ridge of high pressure helps to weaken the cross Cascade pressure gradient that has been fueling the rapid spread of these fires.

While the winds have weakened compared to yesterday, models are still showing some gusty winds near the gorge during the day today.

However, by 8pm tonight, notice how those east winds have started to diminish.

Weakening winds should make a significant difference in helping firefighters get a handle on some of these out of control blazes. However, as that ridge continues to build, our flow will start to shift from easterly to northeasterly. The first model image is for 11am local time, while the second is for 11pm local time.

Notice how that very heavy smoke from Western Oregon stays south of Portland this morning, but by tonight, that incredibly heavy smoke plume makes its way north to Portland. Smoke can be pretty unpredictable sometimes depending on fire behavior, but I think it is safe to say that air quality will get considerably worse in downtown Portland and on the north side of the metro area this evening as our flow continues to shift.

Whether that heavy smoke makes it up to the Seattle metro area remains to be seen. Regardless, bad air quality will be the name of the game for the next few days.

Just to put those model images above into perspective. This video from Portland to Salem shows just how thick that smoke plume is.

The other weather story is this late season heatwave that will really get going today. Right now it looks like highs will reach the 90 degree mark today and tomorrow, which puts us in record high territory. The currently record high temperatures in Seattle are 89 for Wednesday and 85 degrees on Thursday. We may not break the record today, but we will likely break our record for Thursday.

With all of these evacuations taking place in Oregon, its a good idea to familiarize yourself with the levels of evacuation. This graphic from Snohomish County Emergency Management describes each of the 3 evacuation levels.

Level 1: Ready

Level 2: Set

Level 3: Go

Onshore flow will start to filter into the interior lowlands on Friday, which will help significantly with controlling these fires through the weekend. Stay safe everyone!

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