9pm Sunday...

The long Thanksgiving weekend is coming to a close this evening. We've had some pretty good weather! A dry Thanksgiving Day, then lots of sunshine in the metro area Friday. A weak system gave us a drippy day Saturday, with about 0.10" total in Portland, then bright sunshine again today. Of course it's been a different story south of town. Two of those days the fog & low clouds just wouldn't go away. In fact today the southern edge of the metro area could be seen sitting in fog/clouds from our Skyline camera

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Next spring when I look back for a winter recap, it's obvious November will go down as a boring month. Sure, we had a couple of windstorms at the coastline, but no gusts above 37 mph in Portland. Temperatures ran near normal across most of Oregon and Washington

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Rainfall ends up near normal as well...

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...although slightly below in Portland

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What's Ahead?

A weak system moves into the region tonight, bringing a quick shot of valley rain and mountain snow, you can see the dip in the upper-level flow over us tomorrow

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By Wednesday a strong upper-level ridge will have developed overhead

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And it sticks around through the end of the week.  8 days from now the ridge is still there, although weakening quite a bit

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It looks most likely that we won't see significant rain again until about the middle of NEXT week; 9-10 days away. So it's clear December will start quite dry. Notice lots of ensemble members from this morning's ECMWF model show rain around next Tuesday/Wednesday.

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Models have been consistently advertising that change about 10 days out for several days now. Will the upper-level ridge back to the west and allow some cold air to come down from the north, or do we go back into some sort of wet westerly flow? Too soon to know, but I'll be watching that closely

In the meantime, the strong ridging means a classic "gap wind" event is on the way for the Columbia River Gorge. High pressure pops up east of the Cascades behind tomorrow's system. For the first time this season a cold surface high develops late Tuesday and into Wednesday over the Columbia Basin of Eastern WA/OR. The WRF-GFS has been showing about 10 millibars worth of pressure gradient through the Gorge by sunrise Wednesday. That's the only one sea-level gap through the Cascades and all the wind is headed there.

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At the same time, temperatures at 850mb overhead reach around +10 or so, that will be quite an inversion! It's a classic setup for extra-strong east wind in the western end of the Gorge plus out into the east Portland/Vancouver metro area. Check out the thin layer of easterlies in the WRF sounding from Wednesday afternoon to Saturday.

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When the east wind layer is "squished" relatively low to the ground by the strong inversion, two things happen:

1) We don't get a widespread wind event like Labor Day, but most wind remains confined to central/east metro and the West Hills.

2) The wind is even stronger IN THOSE AREAS as opposed to when it's widespread over the entire metro area. Same volume of air is forced into a smaller "channel" = stronger wind.

Expect wind gusts 35-50 mph east metro and 60-80 mph in the west end of the Gorge Wednesday-Friday. Yes, this setup should produce 100 mph gusts on the steps of Vista House. If not Wednesday, then Thursday or Friday. The wind sensor there is offline, but the new part should arrive this week, hopefully it'll start working again.

TO SUMMARIZE

  • There's no sign of a stormy weather pattern and/or lowland snow/ice in the next 10 days. That's through December 9th
  • Other than light rain tonight and Monday morning, we should be mainly or all dry for the next week
  • Expect lots of sunshine most areas west of the Cascades Tuesday afternoon through the rest of the week
  • Prepare for a very strong "winter-strength" east wind episode for at least 4 days starting Tuesday afternoon in east metro and western Columbia River Gorge

That's it for this evening, I'll be back on TV at 10pm. Enjoy the rain later tonight and bright sunbreaks following the showers tomorrow afternoon.

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