Hot For A Day Tuesday, But Another Cool Weekend Ahead

June 22, 2020

9:30pm Monday…

As expected, after a bunch of rainy weather in June we’ve dried out quite a bit in the last week. PDX picked up a third of an inch on Saturday, but otherwise it’s been dry since last Tuesday. That’s good, since we’re now sitting on our fifth wettest June (of the last 80 years) at PDX.

A large ridge of high pressure is covering the entire Western USA right now. This is our midsummer weather pattern. Hot weather for all except coastal locations and areas near the Canadian border.

Today we hit 86 in Portland, 11 degrees above the average for this date. What changes tomorrow? Well, the 850mb temperature (temp in Celsius over Salem around 5,000′) on the afternoon sounding was +18. Models are forecasting about 4 degrees warming at that elevation tomorrow, and 3-6 degrees down here at sea level. That puts us somewhere between 89-92 for a high at PDX tomorrow. Seems reasonable so we are forecasting 91.

We get a moderate marine push tomorrow night and Wednesday as a weak system “dents” the upper-level ridge. High temps only 75-80 degrees with a cloud/sun mix is the result that day. Then the ridging pops up again Thursday-Friday for a return of 80 degree weather.

Then it gets a bit more interesting. A pattern that would possibly bring us snow or arctic air in winter sets up Saturday through Monday. A cold upper-level trough drops down out of Canada, centered over Eastern Oregon by Sunday. If it stays that far east, we won’t be very wet west of the Cascades. But the entire region will be unusually cool for the final days of June.

The ECMWF is forecasting an 850mb temp over Salem down around +2 to +3 on Sunday morning. It appears it has not been down to zero in late June in the past 60 years, so this is close to the coldest it can get this time of year overhead.

Will this ruin your outdoor event either Saturday or Sunday? Possibly, although right now models are dumping a ton of rain west of the Cascades in the I-5 corridor since the center of the real cold air is farther east. Areas without color on this map from the ECMWF model indicate less than .10″ rain. Most of it falls Sunday.

IF YOU HAVE AN EVENT OR PLAN ON CAMPING IN THE FOOTHILLS OF CASCADES OR IN THE MOUNTAINS, there’s a good chance for a soaking. Not so much in the middle of the Willamette Valley and west of I-5. Unfortunately once again it doesn’t look like great “lake weather” in the Cascades. This is total rain forecast by one model ending one week from now.

Sorry about the timing! A summer weather pattern weekdays and cooler temps weekends has been the theme lately. Be safe jumping in local lakes/rivers on these warm days, they are slow to warm up in June. The numbers today:

That’s it for now. I’m off tomorrow, but back on Wednesday-Thursday this week, I’ll try to update again before the weekend.

By the way, keep an eye to the sky the next couple of weeks when we have clear evenings. There have been lots of noctilucent cloud sightings recently around the northern hemisphere. They are typically seen between 10-11pm after the sun has set and you can’t see “regular” clouds well. Suddenly thin blue clouds may appear in the partially lit sky. We’ll see.

Chief Meteorologist Mark Nelsen