It’s the most boring time of year weatherwise, but thought I’d try to find something interesting to chime in about.

First of all…our June in The Dalles was slightly warmer than average, but definitely not hot. Averaged high of 81.4 and averaged low of 55.9, added up to 1.7 degrees F above normal. We had one significant cool spell in the 2nd week of the month, with nights as cool as 43. There was no prolonged heatwave, just a few 90-plus days scattered here and there (including a 99 on the 24th).

Precipitation was actually pretty close to normal, thanks largely to some thunderstorm activity in the middle of the month. But it won’t be enough to “erase” the droughty, high-fire conditions that were created during the latter half of spring.

We have some curious developments on the way for July, it seems. Originally the “game plan” for this summer was to have lots of hot weather in the Western U.S. The seasonal temperature outlook maps showed solid red anomalies over the Pacific Northwest and Northern Rockies alike. But…take a peek at what our revised July outlook has to offer:

Hmmm…VERY interesting. If you’re a seasonal weather geek like myself, that map looks a whole lot like the 6-10 day maps do in early fall, when chilly Canadian high pressure begins diving southward into the Rockies. That pattern usually brings a dry east or northeast wind to The Dalles, with cooler-than-normal nighttime temps.

And oddly enough…today’s weather was actually more characteristic of September than of July. There was very little wind in The Dalles, and yet temps only managed to make the low 80s by afternoon. That’s extremely rare at this time of year; usually when the wind stops it at least jumps up into the low 90s. Even more telling…Spokane had a high of 68 degrees today and Sandpoint, Idaho never got out of the low 60s! Both places are normally close to 80 at this time of year. That has ‘Canadian Cool Spell’ written all over it.

The short-term effect of this has been to shut off the normal west-to-east pressure gradients in the Gorge, since there is higher pressure to the north-northeast of us. Dewpoints have dropped into the low 20s today under the light northerly breeze. With low humidity, little wind and a not-too-hot atmosphere overhead, temps tonight should get quite cool for early July. I wouldn’t be surprised to see 50-52 degrees for a low at DLS airport, maybe even a 49!

The pressure maps are undergoing a rapid evolvement over the 48-hour period from this morning to tomorrow night. Here are the WRF-GFS maps showing it. First, 11am this morning:

Notice how there are no tightly packed isobars through the Gorge. That was indicative of the nearly windless day we had today. Pressure gradients were nearly flat due to a weak high-pressure center directly over northeastern Oregon.

Now at 5pm:

Not much different, the high pressure is still centered slightly to our east, but not strong enough to give us much of an east wind.

11pm tonight:

Notice an area of lower pressure trying to poke up into southern Oregon from California. This is normally what happens when we’re about to have a big heatwave in the PNW.

5am to 11am, tomorrow July 4, is when things get curious:

We have a weak low-pressure center to the south-southwest, and now there’s cooler Canadian high pressure to the northeast as well. This is going to set up a northeasterly upper-level flow tomorrow morning, coupled with brief east wind in the Gorge. I say brief, because….

By 5pm an area of hot surface low pressure (thermal trough) has developed over Eastern Oregon, and is beginning to put an end to the Canadian airmass party. By 11pm tomorrow night we’re back to a pretty typical summertime pressure map, with a bubble of hot air to our east and moderate westerly wind through the Gorge:

So…we have an attempt tonight and tomorrow, to throw a fall-like Canadian trough into the mix. But it quickly gets ‘beaten back’ by the midsummer sun, late tomorrow and Thursday. Needless to say, with the low humidity and dry east wind tomorrow, it would be very stupid to get careless with fireworks…be safe!

As for the long-range forecast? I don’t know for sure if the cool Northern-Rockies pattern is going to hold. The current 6-10 day maps look pretty hot in our greater region. It appears that the hot weather in the Midwest and East, may in fact migrate westward for a while as we move towards the 2nd week of July. That would likely mean plenty of upper 80s/low 90s for Portland, and some mid 90s to low 100s for The Dalles and points eastward.

In any case…we don’t know exactly which way the rest of this summer will roll. Stay tuned!