Whew, what an unusual season it has been!  As of October 19, Portland International Airport is running 8.7 degrees F above normal, by far the warmest early/mid October period in recorded history.  Today, October 20, was the last warm day before cooler and wetter conditions arrive tomorrow.  Yesterday was the last “really” warm day…at 75 degrees, it was 12 above normal and only 3 degrees shy of the record.  It sure didn’t feel that toasty, though – at least not after our historic heat last weekend (87 & 86 at PDX!)  If we had had a cool and wet start to October with lots of days in the upper 50s/low 60s, and then jumped up to 75 midmonth, we would be aweing about how fantastically warm it felt.  (Not to mention there would be lots more fall colors and likely no wildfire smoke.)

Speaking of smoke…after the Nakia Creek Fire exploded last Sunday, the smoke settled in the western valleys this week.  Air quality in Portland and Vancouver was in the “unhealthy” to “very unhealthy” categories for most of Tuesday-Thursday, and has only begun to improve this evening.  Seattle and the Puget Sound have been just as bad or worse due to the Bolt Creek Fire.  Yuck!  It’s not as bad as the hazardous air quality we had during the September 2020 megafires, but it was still pretty awful.

The air should gradually clear up tomorrow and over the weekend as the cold front and incoming rain begin to sweep out the low-level inversions that have trapped the smoke near the surface.  Rain should arrive in the metro area some time around 9-11am tomorrow.  Here is the 12z GFS map from this morning, for 11am tomorrow:

Tomorrow’s rain will usher in a more progressive storm track, and one that has a cool northerly connection.  High temperatures should drop into the mid/upper 50s over the weekend.  We might get a break from the rain on Sunday before the next slug of rain arrives Monday.  Here are the 7-day rain totals through 5am next Thursday morning:  first the GFS, then the ECMWF:

The ECMWF is slightly wetter for Portland while the GFS is wetter for the southern Willamette Valley and SW Oregon.  But the theme is similar:  cool and wet weather is finally here!

The airmass will become quite chilly over the weekend and again early next week, with temperatures at 5,000 feet dropping to near 0C or slightly cooler.  That means snow could fall to 4,000 feet or lower over the Cascades and parts of the high desert in central/eastern Oregon, as well as the Blue Mountains.  I don’t have a ECMWF snow map, but here is the 12z GFS for the next 7 days:

Be prepared for some possible winter driving conditions over Government Camp and the Oregon Cascade passes if you are headed that way.  That said, after all this warm weather the snow may have some trouble sticking to pavement, especially for the first couple days.

Models are in disagreement as to what happens late next week into the following weekend.  But that is to be expected in an active fall/winter pattern like this.  I’m quite confident we won’t see any more 75-degree days, and probably not 70 either.  But we could still see some days in the 60s as we head toward early November, if conditions clear out again and we get some offshore flow to keep the fog at bay.

For one last look back at our unusually warm first half of October…here is the data for Oct. 1-16 for several stations across the Pacific Northwest:  Portland Airport (NWS Portland NOWdata); Sea-Tac Airport (NWS Seattle NOWdata); Rogue Valley Regional Airport (NWS Medford NOWdata); as well as The Dalles Airport and Redmond Airport (NWS Pendleton NOWdata).  All of them show the same theme:  historically warm and dry conditions, with an abnormal number of days in the 70s and 80s (and in some cases 90s!).

(Please forgive the uncropped screenshots; I’ve been very busy today and didn’t have time to edit them!)

ONE FINAL NOTE:  This will probably be my last weather blog for a while (at least a month or two) due to some other priorities in my life.  I’m starting a new job next month, and also want to focus more extensively on my music & social life.  I am not going to do a “winter outlook” this season, though I will say that it will be our 3rd consecutive La Niña winter.  If you want to learn more, come to the 30th annual AMS Winter Weather Conference at OMSI, this Saturday, October 22 at 10am!  I will be there and you’re welcome to hang with me.

Enjoy the turn of seasons this weekend and next week!

Karl