Summer Weather Heating Up

July 13, 2020

9:30pm Monday…

I’ve seen quite a bit of complaining about Summer 2020 so far. A wet June was followed by a cool July start. In fact this month is running 2.5 degrees below average; the coolest start to summer in 8 years. Summer is defined by June 1st through July 12th in this case. We have seen 5 days of very pleasant weather with temperatures near normal though.

Today’s 80 degree high under mainly sunny skies was about as “normal” as it gets for July 13th.

A clear shift into the dry season arrived right on schedule though. We have seen less than .10″ rain in the past three weeks! And I see very little in the next 1-2 weeks. Check out the very dry ensemble rain forecast from the ECMWF model. It shows 51 different ensemble members as horizontal lines through the next two weeks. Only TWO of those members produce any significant rain over Salem (Portland is similar) and it’s brief. Most likely attempting to bring thunder up from the south.

So what’s ahead? A quick summary:

The next two weeks will feature the weather some of us wait for. Expect reliably dry and warm weather with near to above normal temps…plus abundant sunshine. This is it folks!

What has changed? All models are, in general, keeping upper-level heights quite high over us the next two weeks. A hot ridge of high pressure doesn’t seem to want to sit directly over us for a major heat wave, but heights remain high. Here’s the GFS ensemble 500 millibar chart for tomorrow

The cool trough that brought us sprinkles/showers Sunday morning is over the Rockies and northern Plains. A warm upper-level ridge is sitting just to our west over the Eastern Pacific. It’s not right over the West Coast, but heights are above average for mid July (the warm colors) over us. Then look at Thursday night; a fast moving upper-level wave rides over the ridge. In summer this means a strong marine push of cooler ocean air, but typically no rain.

By this Sunday (the 19th) the ridge is rebounding and moving closer again. Notice heights are up to 588dm. That means the 500 millibar pressure level is way up over 19,000′; a warm/hot airmass is pushing overhead with the core of the warm air offshore.

By Tuesday the ridge offshore is a bit weaker and farther away. But the main thing to see here is that upper-level heights are above average all across the region. This is a warm weather pattern through these 10 days, but not excessively hot.

With that ridge nudging a bit closer to us next Sunday-Tuesday, we may turn hot for a brief period. It’s not real tough to see a few 90-95 degree days in late July in Portland! This is what we’re thinking right now for Portland:

Enjoy the dry and warm summer weather!

Chief Meteorologist Mark Nelsen