The forecast was perfect until about 3pm…then it went down the drain quickly. A shortwave passing overhead allowed clouds and showers to build, mainly over the mountains. But a few popped up here and there over the Valleys. Around 5-6pm strong thunderstorms developed over the North Coast Range…looks like Mist and Vernonia really got hammered. As of 10pm it’s real quiet with just a few sprinkles over the central Oregon Cascades. A unique feature this afternoon was a low-level gust front that moved through the Metro area from the intial batch of showers over the Mt. Hood National Forest. You could see it on the radar and in observations on the east side of town. It came in from the southeast, very obvious from the Corbett observation between 3-4pm. The all-day long east wind (in comes in from the East to Northeast) suddenly went SE or briefly even south and the temp dropped. Similar thing happened in Troutdale and the Eagle Creek RAWS obs. I was riding my bike along Skyline from Cornelius Pass to Cornell during this time. The breeze and cooldown were noticeable even up there.
I have to admit our RPM model nailed the showers and I pretty much ignored it yesterday evening. So what does it show for tomorrow? The upper trough shifts east a bit and seems to take MOST of the instability with it. However it shows some convection over the North/Central Coast Range and Cascades drifting off to the east. Not as impressive as today but I sure wouldn’t do a project outside that REQUIRES dry weather. Most likely most of us stay dry, but watch out in the mid-late afternoon.
Sunday the convection should slip farther south and east, in advance of a cold front that moves in Sunday night.
It appears that weak upper-ridging takes hold the rest of next week. Not real high upper-level heights, but dry weather and mostly sunny skies. ECMWF 850mb temps were the highest…as high as +13, giving us highs over 80 degrees, but GFS is a bit more subdued. A +8 to +10 is more in the 75+ range. We (Drew and I) took the middle road and went with mid-upper 70s later next week. My garden could sure use it and I’d be perfectly happy with a string of 70 degree days. I’ll take anything between 65 and 85 in the month of May without complaining.
Chief Meteorologist Mark Nelsen