I hope you’ve been making the most of this once-in-a-lifetime October weather!  Granted, for some of us (especially in the Puget Sound and the southern Willamette Valley), the persistent wildfire smoke has been pretty rough.  And there are plenty of weather geeks who are eager for cooler, wetter conditions to arrive.  I, on the other hand, appreciate the unseasonability of this fall.  It has really tested previously-held assumptions of what is possible in our climate region.

Today we hit 82 degrees F at Portland Airport, making today the tenth 80+ day in October thus far.  Up until this year, the record for 80+ days was only six days – most recently happening in 1991.  Furthermore, the running average for the first 14 days of October is nearly 81 degrees F, which is about the same as a normal July or August (at least prior to the past 10 years, when summer temps began to skyrocket!).  Even our nighttime temperatures have been about as warm as a normal September.  Combine with the total lack of rain, and it’s fitting that the label “Augtober” is trending recently.

Even more outstanding?  The Dalles Airport has not had a single day below 80 degrees this month.  Further south, in the Rogue Valley, towns like Grants Pass and Medford have had numerous days in the low/mid 90s.  This unusually warm and dry weather has had two major effects:  first of all, fall foliage colors are way behind schedule compared to a normal mid-October.  Sure, there are a few “early birds” beginning to change…the same early trees that normally begin to show in late September.  Even in Bend, where I spent the day on Sunday the 9th, I was amazed at the lack of significant color.  Bend is much higher in elevation and has much cooler nights, so you’d expect there to be lots of color by this time.

The other big feature has been a prolonged fire season and wildfire smoke.  The two biggest fires – Cedar Creek in the central Oregon Cascades, and Bolt Creek in the Washington Cascades – are still plaguing cities like Eugene and Seattle with lots of smoke and difficult air quality.  Last Sunday there was even a new fire in eastern Clark County, about 15 miles east of where I live, called the Nakia Creek Fire.  Fortunately it didn’t blow up out of control, but it’s a reminder of how unusually late the fire season is dragging this year.

We even have a Red Flag Warning up for the Cascade foothills and western Columbia River Gorge tomorrow and Sunday due to the expected return of dry east winds.  More on that in a moment.

What is the cause of all this wildly warm & dry weather?  We have a massive “Rex Block” ridge anchored along the West Coast of North America.  These ridges are notoriously persistent, and can last for two weeks or more under the proper circumstances.  Here is the 500mb anomaly for this afternoon.  The big red zone is an area of unusually warm air.  Warm air bubbles up into the upper troposphere more easily than cold air, which tends to hug the ground.  As a result, warm upper-level airmasses tend to exhibit higher pressure three miles above the surface.

That ridiculously resilient ridge is not expected to budge much for the next 7 days, except for a brief push of marine air on Monday and Tuesday.  By Wednesday afternoon the area of ridging has actually expanded across the western half of the continent:

But look what happens come next Saturday.  It appears the ridge will FINALLY back off to the west, allowing cooler air and moisture to come in from the north/northwest:

Long-range models have been hinting at a pattern change beginning around the 21st/22nd of October, for several days now.  There has been a lot of disagreement as to the details, however:  we could either see zonal flow directly out of the west, or we could see cooler troughing digging down from the Gulf of Alaska and Western Canada.  Either pattern could give us decent rainfall, but zonal flow tends to be wetter and milder than deep troughing.

The ensemble “spaghetti map” for the 12z GFS clearly shows the pattern change around the 21st, with much cooler air moving in at the 850mb (5000-foot) level:

I don’t have easy access to the ECMWF spaghetti charts, but those models have been showing rain and cooler air as well; in fact, the Euro models tend to be somewhat cooler than the GFS.

…Before the pattern change, though, we have one more extremely warm bout of weather to get through.  East wind is expected to develop tonight into tomorrow, and continue through Sunday morning across the Portland metro area.  At the same time, 850mb temps are going to be around +19 to +20 degrees Celsius.  This combination could easily push us to around 92-94 degrees in the middle of summer, but it’s mid-October and the sun is much weaker.

The WRF-GFS image above shows especially warm air to the south of Portland.  In fact, the HRRR model is showing temps close to 90 degrees tomorrow in Corvallis and Eugene!  Portland is shown as being slightly “cooler” due to extra east wind near the surface.  But we should still make it to the mid 80s quite handily.  Then Sunday should be similar at least in Portland, perhaps slightly cooler to the south as marine air begins to seep in.

We’ve never hit 85 later than October 11 at PDX, so this weekend should be historic to say the least – record highs at this time of year are in the upper 70s/low 80s, and normal highs are around 65.  Much like last April’s snowstorm, this October is truly testing the limits of off-season weather in our region!

Definitely try to enjoy the summer-like weather for one last weekend.  Just don’t do anything that involves starting fires, due to the Red Flag Warnings nearby.

Monday and Tuesday we should cool into the low 70s as marine air seeps in.  Then Wednesday and Thursday we warm back into the upper 70s/near 80 again.  That means at least two more daily records will fall this weekend, perhaps one or two more next week.

Evidence is growing on the models that we will see some sort of change to cooler/wetter beginning next Friday or Saturday.  What is still unclear is the total amount of rainfall in our immediate area, as well as the temps/snow levels.  If we see a milder and wetter solution, then October 2022 will almost certainly go down as the warmest on record.  If we get a cooler pattern with deep troughing and snow down to the Cascade passes?  We could still theoretically beat the all-time monthly mean record from 2014-2015 (60.1 F), but it will be a closer call than in the mild zonal scenario.

That’s it for now…I’m off to visit family in The Dalles tomorrow!

Take care,

Karl