Making my forecast here at 3:30pm (I work Sundays-Thursdays now) and I’m noticing it’s sunny just about through our whole viewing area. This is on the day that we figured would be quite cloudy and cool. We got the cool part right; but not the clouds. I doubt anyone is complaining but let me explain…
During a good chunk of the summer we are under a marine inversion…quite strong on the coast and it comes/goes in the valleys. That means relatively warm air is sitting over the Pacific Ocean-chilled airmass down near sea level. But you can see what has happened today on the Troutdale profiler image below. Time goes from RIGHT TO LEFT on this graphic:
This is temperature (well, virtual temperature but more/less the same thing) and wind direction/speed from the surface up to around 5,000′. Note that yesterday AM/Midday it was cool above up around 4-5,000′, as you would expect. But there was a second area just about as cool down around 3,000′. That was the top of the “cool” marine layer. It mixed out nicely in the afternoon, but you can definitely see the weak inversion. Today is totally different with much colder air arriving above 3,000′. You can see temperatures go from real chilly at 5,000′ up to reasonably cool down here at the surface AM/Midday today. The result is a weak to non-existent marine inversion today. That allows mixing and drier air to break up the cloud cover. The end result is a sunny and pleasant 2nd day of the 3 day weekend!
The next 2-3 days appear to be similar, so I’m sticking with the morning clouds to afternoon sun routine through Wednesday.
Chief Meteorologist Mark Nelsen