Hopefully everyone here has been able to enjoy the (mostly) smoke-free weather in Northwest Oregon and SW Washington this summer!  Sadly, I’ve been having knee problems ever since the beginning of July, limiting my mobility to a fair extent.  But I still managed to get out and enjoy it within reason.

Last weekend I was at the Oregon coast (again!), this time in Oceanside and Pacific City exclusively.  Fellow weather blogger Charlie Phillips knows that area well thanks to some old family ties, and he was able to recommend a “secret” hike on Cape Kiwanda for some stunning vistas.  It was a normal onshore flow day this time around, with 30+ mph NNW wind gusts and temps in the 60s.

The cover image of a Gorge sunset, though, was taken Sunday, August 1 near White Salmon, WA.  I was visiting old friends in the White Oak Grove for our Lammas potluck; that symbolizes the dog days of summer and the beginning of the harvest season.  The faces have changed quite a bit since I first started going in 2014, but the general vibe of the group is still very much carrying on.

Late July and early August are the normal peak of summer temps in this corner of the world. Portland’s average daily high temperature is 84 degrees F now….a full 2 degrees F warmer than under last decade’s climate normals.  That said, it’s just an AVERAGE. Sometimes we hit 100 or higher at this time of year. And sometimes, we even have periods of cool and overcast weather in the peak of summer. In fact, we’re going to see precisely such a cooldown later this week- with Portland’s first solid chance of rain showers in 7 weeks!

THE OUTLOOK 

1.  We have three more days of warm weather and hazy sunshine; expect temps in the upper 80s to low 90s through Wednesday!

2.  Thursday evening will be Portland’s first short at rain. Showers could linger through Friday and early Saturday.

3.  Temperatures will actually drop into the 70s for a few days…the longest stretch of sub-80 weather since mid-June.

4.  Next week it appears we go back into warm/hot weather, but as usual it’s too early for details.

=====

First things first.  July 2021 in Portland ended up at 73.0 degrees F, with an averaged high of 85.5 and low of 60.6.  That makes it the 5th hottest July on record for PDX, in 83 years of records.  The hottest July, in 1985, came in at 74.1F.  What I find most fascinating is that three of the four hotter Julys, happened in just the past 12 years.  Had July 2021’s temps occurred in 2008, for example, it would have been the 2nd hottest ever.

And yet, this July was only 2.8 degrees F above the new 30-year normal, and had only 6 days 90+ and no days at 100.  It was just consistently warm all month, with all but four days at least reaching 80 degrees.  It goes to show how rapidly Portland’s summer climate has changed in just the last decade.  We are basically a “true” Mediterranean zone now.  Every August since 2012, and all but two Julys, have been at or above 70.0F.

Today’s upper-level pattern is very much a proxy for our overall July pattern. Weak warm anomalies in the upper troposphere (about 3 miles above sea level), with warm temps in the lowlands but no extreme heat:

But by the end of this week, our medium-hot pattern is replaced by a cool one.  An upper-level trough of cool air moves in from the Gulf of Alaska. This is the exact same pattern responsible for the best Cascade snowstorms in winter. In August though, it just means a few days in the 70s with light showers.

This trough of cool, low-pressure air in the upper atmosphere is still with us next Monday afternoon, even if the showers are gone:

This means we should cool down to below normal (i.e. mid to upper 70s) for at least Friday-Monday.  The system moving in late Thursday also has some precip; notice that nearly everyone in and west of the Cascades gets wet Thursday night and Friday:

It’s only light rainfall of 0.05-0.2″ for the Willamette Valley, so there’s always the possibility that no rain could make it here.  However,  ensemble models show a fairly distinct signal for light rain Thursday-Friday.  The 00z GFS from last night shows the blue line at the bottom bulging up a bit.  It’s not a case of a few wet “outliers” driving the signal.  Most members hint on something happening, albeit not very much:

Again…Friday seems to be the epicenter of the precipitation, though it could begin Thursday evening and/or continue into Saturday.  The shift to cool temps should feel very refreshing, regardless of how much rain falls.

Starting next Tuesday or Wednesday,  most long-range maps suggest that temperatures rebound and summer warmth returns. But the verdict is still out as to how warm it gets:  we could just have a bunch more days in the 80s with light marine influence.  Or we could see 90s, possibly even 100, return yet again.  The very long range of the GFS even shows another “heat dome” developing over Western Canada, even if it’s not quite as hot as the last one!

Obviously we’re not going to call shots on a couple anomalously hot maps, until or unless we start to see models lining up behind such a scenario. For now, I’m looking forward to cooler temperatures beginning this Thursday for a few days, and hopefully at least a few rain showers!

-Karl