We saw our first strong Gorge wind of the season in the far east Metro area and Western Columbia River Gorge today. The pressure gradient from Portland to The Dalles was up to -6.7 millibars at one point…pretty good for mid-October and just a sign of things to come as we get deeper into Fall. Of course the big east wind season is in the winter, generally November to February, then it disappears quickly in early March. The reason is the cooling of the continent while the ocean stays about the same temperature (a few degrees cooler). Cooler land = heavier & cooler air overhead = high pressure. Higher pressure east of the Cascades and lower pressure west means wind funnels through the only sea-level gap in the Cascades (the Gorge). The wind then spreads out and slows rapidly, in most weather patterns, as it exits the Gorge. Today was a prime example of a “gorge-only” wind event. Sometimes the east wind also goes over the Cascades, bringing more widespread gusts to the entire Metro area.
Of course the result was a bright and warm Autumn day…temperatures into the lower 70s around town today. I had more than one comment from the public that just loves this weather. Cool and clear in the morning, warm and sunny in the afternoon. The easterly wind also gave us great visibility too.
The wind goes away this evening…in fact the gradient is already down to around 2+ millibars. We go to weak onshore flow tomorrow, so expect a drop in the temps as a front approaches, but still a real nice day, until we get some evening sprinkles.
The 7-10 Day Outlook still looks very boring for us weather weenies. In general a ridge of high pressure or split flow through at least the middle of next week. One change in the weather will be a cooler atmosphere Friday through Monday. That plus relatively dry air and mostly clear skies at night could mean the first frost for outlying areas. I mentioned this on Monday and it still seems likely even now.
Chief Meteorologist Mark Nelsen