(Cover photo credit of Ben Randall)

 

After a slow start, Pacific Northwest summer is in full swing!  The first 10 days of July was the coolest in many years, with only one day in the low 80s, most days upper 60s/low 70s, and tons of low clouds that hardly burned off at all in the afternoon.

 

But now we’ve had many more sunny days in the 80s and low 90s; our classic “Mediterranean ” warm pattern has locked itself in for the most part.  In fact today’s high of 71 was the coolest in 2 weeks!  We’re going to crank the heat up in a BIG way this Sunday and Monday; it just might end up being our hottest weather pattern of the summer if nothing extreme happens in August.

First, today’s 850mb map.  Notice the chilly NW flow coming down from the B.C. coastline.  That’s very similar to the modified arctic fronts we sometimes see in the beginning phases of a major winter cold blast.

 

(All 850mb maps credit of TropicalTidbits.com)

But by tomorrow afternoon the wind is switching to north-northeasterly, and the airmass quickly warms:

Then things go wild Sunday and Monday.  Offshore flow strengthens and the thermal trough forms near the Oregon coast.  This all but guarantees at least 95 degrees at PDX, but 97-100 is very feasible.

Fortunately, it’s only going to be a two-day event for the worst temps.   Tuesday we start to cool off with onshore flow returning.  Probably *only* 90 degrees then:

What this means is a very fast explosion of temperature at the surface. We go from 71 today to mid 80s tomorrow.  Then upper 90s (give or take) Sunday-Monday.  Here’s the sounding over Portland at 5pm on Monday evening, near the time we normally see high temps. It shows a 99, and this is probably the day most likely to see some localized 100s.

East of the Cascades, Monday and Tuesday will be the hottest days instead.  I could definitely see 100-105 degrees in places like The Dalles.

 

The big question is what happens right near the coast. If east wind makes it to the beaches, then 90+ temps can occur right out to the water’s edge. The Sunday surface temp map shows lots of red coming very close to the Northern Oregon coastline.  Maybe it heats up out there, maybe not.  But if you live 4 or 5 miles inland, I’m quite confident Sunday will at least get into the 80s, if not 90s.

Tuesday the return of onshore flow chills the coast and drops Portland about 10 degrees. Then a few degrees cooler Wednesday as the heat wave comes to a close.  Late next week looks very seasonable once again,  with near normal temps over the region:

 

So it will just be 2 or 3 days of misery this time.  Still, we’re not adapted to extreme heat in a mild climate like ours.  Especially not after such a mild first half of summer.  So stay hydrated, avoid heavy exercise and dress lightly unless you are participating in activities which require “full coverage” attire.

 

Stay cool and stay safe! -Karl