A White Christmas In The Gorge, & Some Christmas Evening Wind Westside

11am Christmas Eve (Thursday)

Merry Christmas! It’s almost here, although a much changed version from any other year…very quiet for obvious pandemic reasons. It’s a dark time across the USA. That said, it HAS been nice to see bright sunshine the past two days.

I’ve been off the last 6 days, but will be back at work tomorrow evening through the middle of next week. We had quite a well-forecast soaking, warm temps, and gusty southerly wind. Now it’s quiet except for dense fog in the Willamette Valley and strong easterly wind blowing in the Gorge.

A wet weather system moves inland Christmas Day. With cold air stuck in the Gorge, that means some of you will have a White Christmas! In this case I’ll define that as seeing at least a dusting on the ground.

HIGHLIGHTS

  1. Nothing interesting happens through tomorrow morning, except lingering areas of dense fog south of Portland metro and easterly wind gusts 50-70 mph at the west end of the Gorge. Crown Point has gusted to 75mph this morning.
  2. Rain moves inland by late morning tomorrow; it’ll be a gray, wet, & cool Christmas west of the Cascades
  3. As that moisture rides over cold air in place, snow begins falling early afternoon from Bonneville Dam eastward to The Dalles and down into north-central Oregon (Dufur, Maupin). Expect 1-5″ Christmas afternoon through early Saturday morning in those areas. A White Christmas for Hood River, Stevenson, White Salmon, Lyle, & The Dalles. Least would be at freeway level and at The Dalles, most up around 1,000′ and above. Expect there may be some snow on I-84 late tomorrow afternoon possibly through Saturday morning.
  4. Depending on how cold the airmass is, there could be the usual spots of freezing rain/sleet west of Bonneville Dam to hills above Corbett on Oregon side, and hills above Washougal on Washington side of the Gorge. Likely only up above 500-1,000′. East wind will increase further; gusting 60-80 mph midday/afternoon Christmas before suddenly turning light around midnight tomorrow night.
  5. A sudden surge of southerly wind should push up the coastline and Willamette Valley in the late afternoon & evening hours Christmas Day. Most models are relatively weak with the wind, but WRF-GFS suggest gusts to 40 in the valley and Portland metro area are possible around sunset and beyond Christmas evening. We will see…ECMWF isn’t on board

A quick look at the “supporting documents”. Sea level pressure forecast for 10am Christmas day shows a developing low offshore…

Then at 4pm the low has strengthened a bit. Pressure gradient through the Gorge is up to 8 millibars = cold & windy there.

Then at 10pm you see the surge of south wind and tight pressure gradient in the valley. It’s important to note that this model is strong than others. Much weaker low would mean just light southerly breezes.

This WRF-GFS model brings 70kt wind down to around 2,000′. Again, the strongest I’ve seen of all this morning’s runs

As for snow, ECMWF has been looking like this for the past 4-5 days! Several inches in Hood River and an inch or so at The Dalles.

That’s because it’s holding in a cold pool at 925mb tomorrow afternoon and evening. It also thinks Hood River and The Dalles only top out in the upper 30s today. If it gets well into the 40s (today), then it’ll be obvious modeling has been a bit too cold.

The brand new IBM GRAF model (along with soon to be extinct RPM) thinks there will be no pool of cold air east of the Cascades and no snow anywhere near the Gorge. I think the GRAF missed the last snow event out there too.

It’s interesting that the 2.5km (very high resolution) HDRPS model (Canadian) brings plenty of snow to the central/eastern Gorge. Strange little no-snow zone around Lost Lake to Parkdale, apparently punching in a little warmer air aloft.

But just for fun, you can see what it’s doing. Slightly warmer air overhead = sleet. Accumulation graphic here “fills in” those no-snow holes.

The main message when looking at differing models/maps? You should never take any one image and say “that’s going to happen”. Far smarter to stick with ensembles, not just of one model but combine several of them together to get a general picture. In this case, “there will be some white tomorrow afternoon/evening and a little silver in spots east of Portland in the Gorge”.

That’s it for today. Enjoy your Christmas!

Chief Meteorologist Mark Nelsen

108 Responses to A White Christmas In The Gorge, & Some Christmas Evening Wind Westside

  1. Mountain Man says:

    Weird my comments never land where they are supposed to. Reply to Jason just went way down the page. Whatever!

  2. lurkingsince’14 says:

    Things finally starting to look interesting 🧐

  3. Jason Hougak says:

    I sure the blog when Mark used to be part of the fun. I think the trolls kicked him off his own blog. Very sad, we miss you on here Mark. Thanks Rob for joining in on the weather action. This is the best time of the year for weather watching.

  4. Jason Hougak says:

    12Z GFS had 7.5” at PDX through Jan. 14th. Most snow seen yet on the GFS model runs.
    Snow looks likely for the foothills next Wednesday night into Thursday for the foothills with colder weather that weekend with snow down to the valley floor.

    • Chad says:

      Outlier

      • W7ENK says:

        Oh, so you follow the models, but you have to ask whether it’s “South wind or East?” Yet you know how to toss out the word “outlier…” 🤔

        Yeah, you’re not fooling anyone, Chadwiggy. 🤷🏼‍♂️

    • Mountain Man says:

      I know Jason, you are one of the best people who has been here so long like me and Rob too. The trolls are as bad as the sometimes long complaining about the trolls. I still glance every day or two, it used to be better. Mark even used to talk to people. He still does on FB occasionally, where I often go first now. We’re both in the foothills at 1300 ft. Just I’m on a different mountain. Just all the dustings up here like you and nothing for the rest of everyone to do or feel anything about but to be pessimistic about, in a world of different beliefs and hard times. Maybe something exciting will happen and liven things up, this blog certainly needs it and so be out spirits. There’s still time.

  5. Definite wind storm pattern coming up as we move into January. If we want any Cold and SNOW we’re going to need jet suppression and offshore flow, or an anafront setup. We probably won’t see any huge pattern change with the jet retracting until we are closer to mid-January.

    • Chad says:

      How soon do you think the wind will start storming??? Thanks for your input, you definitely know your stuff!!!

      Also are you talking south wind or east?

  6. MasterNate says:

    Has anyone else seen that some of the links from Marks weather page have disappeared? Specifically the links to all the runs of the ECMWF

    • Joshua Lake Oswego says:

      They’re still there. Bullet point immediately below…
      MODEL DATA & METEOGRAMS. Layed out differently than before.

  7. Weatherdan says:

    Interesting pattern changes looking good starting second week of January. Peace.

  8. Roland Derksen says:

    Another chance to see some snow mix in with the rain here tonight- but that’s all. I still have hope for January, though.

  9. Andy says:

    Weather Bell mentioned the SSWE will be changing the amount of cold for Europe and the U.S in the coming weeks. Should be interesting how it plays out.

  10. W7ENK says:

    As Rob just said earlier, (and as I mentioned about a month ago) </a href> there are now signals of an imminent Sudden Stratospheric Warming Event (SSWE) underway. Current forecast calls for a full disruption and complete reversal of flow in the Polar Vortex, i.e: a Major SSW event.

    https://www.severe-weather.eu/global-weather/stratosphere-major-winter-warming-watch-january-2021-fa/

    As I said last month, when this happens, it presents our best chances for a bona-fide Arctic blast into the Western Valleys of the PNW. I agree with Rob, there is strong potential for a significant pattern change in the next 10-14 days, so keep an eye out!

    • Chad says:

      Believe in your dreams

    • Anonymous says:

      I feel a little icky after reading that severe weather Europe link. It’s as if Kevin Martin wrote it but sounded a little more educated and less hateful.

      • W7ENK says:

        Oh, that’s definitely not K-Mart. Quite a well thought out article based in solid science, and if said conditions materialize, which they seem to be doing so, it’ll change out the whole deck Mark just laid out going forward, at least temporarily.

  11. W7ENK says:

    New world record surface High pressure reading occuring at present in the Tosontsengel region of Western Mongolia.

    Station at Tsetsen Uul reporting 1093.5 hPa
    00z reading at Tosontsengel 1091.9 hPa

    This region is the current world record holder with surface High pressure reading of 1084.8 hPa back in 2001.

    That’s pretty amazing, especially considering they’re at almost 6,000′ elevation!

    • JohnD says:

      Fascinating! Implications?

      • W7ENK says:

        I guess if it were to move North it could disrupt the Polar Vortex and displace Arctic air, shoving it Southward? Knowing our luck, it would all dump down the back side of the Rockies and out into the Plains. In that case, implications would be negligible for us.

  12. Jason Hougak says:

    Next Wed./ Thursday is looking interesting. The models have been consistent on lower snow levels. In any event looks like La Niña is going to come in like a lion for January

  13. Chad says:

    Rob are we still looking at a windstorm chance? I know you’re focusing on cold and snow but that’s a long way out, just hoping for some action before.

    And like my lover says, 45 days after a windstorm is a snowstorm 😜

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