Slow Weather Pattern Returns For Christmas Week

9pm Sunday…

Here we are, Christmas is just three days away!  The atmospheric river and flooding was sure exciting (although mainly north of us).  But now it appears the dull weather pattern we’ve seen since early October has resumed and will be with us for the next week or longer.

A weak upper-level trough is passing overhead tonight and early tomorrow; that brings a few light showers.  In the mountains maybe 3-6″ new snow by midday Monday.

RPM Snow Accumulation Mt Hood Zoom In

That snow is much needed for Christmas Break skiing.  You can definitely go ski/snowboard right now, but coverage is thin at lower elevations.  Skibowl and Hoodoo have not opened yet.  These next two weeks are critical for ski areas since so many people want to hit the slopes while on vacation.

At the 5,400′ elevation, a SNOTEL site has 22″ snow on the ground.  That’s the lowest snowpack in the past five years (on this date).

Mark Mt Hood Snowpack December

It’s more typical to see 4-5′ snow on the ground at that elevation.  There is just about no snow below 3,000′ in the northern Oregon Cascades; you can see that area is running only 25% of normal.  Only SE Oregon is seeing a typical snowpack for the last week or so of December.

or_swepctnormal_update (1)

What’s ahead?  After tonight’s system leaves the area, a 2nd even weaker system drops down toward California on Tuesday.  That one stretches apart, weakening as it moves onshore.  It’s possible we get no rainfall from this one.  Or just a few afternoon/evening sprinkles as Christmas Eve begins.  The evening GFS models gives us less than .10″ rainfall between sunset Christmas Eve and midday Christmas Day.  Obviously a non-event.  With morning fog/clouds leading to late afternoon/evening showers, it’ll be a very chilly Christmas Eve.  One would think it could snow that day, but checking soundings it appears that won’t be possible after midday or so.  A bit too warm overhead plus that above 32 degree airmass continues through the night and into Christmas Day.  This is assuming precipitation makes it inland!  That may not happen.

gfs-deterministic-oregon-precip_24hr_inch-7296800

Beyond that I see some weak upper-level ridging Thursday-Saturday for mainly or all dry weather.   The ECMWF ensembles for 500mb height Saturday…

ecm_sat_28

There are hints of some sort of pattern change right around the New Year.  But that’s 10 days away and a bit suspect considering how this season has gone.  I do see the GFS ensembles going for a rainier pattern about that time.  The lower part of the chart shows the ensemble average rainfall heading uphill next week.  We’ll see…

gfs-ensemble-all-KPDX-indiv_qpf-7016000

So how about travel weather?  MUCH better this week than that terrible Thanksgiving week.  Remember I-5 closing south of Ashland and I-84 issues in Eastern Oregon?  None of that this time.

First, the Cascades.   Roads should be snow-covered by morning and stay that way most of the day.  But I only expect 3-5″ at most tonight.  Not exactly a snowstorm.

Mark Road Holidays 1

Then that snow works off the highways the rest of the week.  That weak system Christmas Eve might drop an inch…maybe.

How about the Gorge?  Should be just fine for travel this week unless a skiff of snow accumulates with that Tuesday night system.  Or it’ll just stay dry.  Regardless, little effect on travel.  Farther east, I don’t see any organized weather system bringing snowfall into the Blue Mountains of NE Oregon

Mark Road Holidays 2

I-5 will remain bare north to Seattle and likely south into California as well.  That weak system moving onshore Tuesday midday/afternoon COULD drop some wet snow on the higher Coast Range summits, but I doubt that will cause any significant travel issues there.  Those Coast Range highways should be clear the rest of the week/weekend.

Mark Road Holidays 3

There you go…no White Christmas (sticking snow) for the western lowlands of Oregon/Washington, but maybe a dusting in the Gorge.  Maybe…

Merry Christmas!  I’ll be back at work Thursday

Chief Meteorologist Mark Nelsen

66 Responses to Slow Weather Pattern Returns For Christmas Week

  1. Jason Hougak says:

    18Z GFS was a great for higher elevation snow. Definitely love the trend.

    • OLIVER WATSON says:

      Unfortunately the 18z gfs is usually refered to as the drunk uncle in the longer range. The 18z and 6z are usually the less accurate models and those are the ones in the last day or so that have been showing the colder and wetter solutions. The 12z and 0z are more accurate and those have been showing the warmer drier forecasts.

  2. OLIVER WATSON says:

    I would like to know marks thoughts on which model seems to be the better one and why they keep bouncing back and forth

  3. Jason Hougak says:

    12Z GFS 3’+ of snow in the Cascades… woohoo NW flow!

  4. Jason Hougak says:

    The 06Z GFS shows cold NW flow returning, in any event it’ll be great for building snowpack. We’ll just have to watch how it all comes together. No signs to throw in the towel yet.

    • OLIVER WATSON says:

      6gfs was ok. 12gfs pooped on us again. Unfortunately the 12gfs is usually more accurate 😟

  5. OLIVER WATSON says:

    Yeah the gfs was showing the goods yesterday then it pooped on us today. Looks like the euro is following suit

    • Joshua Lake Oswego says:

      I have been saying for a while that the ECMWF is trash for the Portland metro area. I swear if you look back at least the last 2 months, the ensembles will have overdone the forecasted precipitation for the forthcoming 15 days by a magnitude of at least two for every single day in that period of time. The high res model is always hugely optimistic as well. The GEM is also garbage. The GFS is the king (operational and GEFS). For high res models, I have found the NAM-WRF to be superior to the HRRR and the WRF-GFS. Anecdotal of course.

    • Evan -- Cedar Mill says:

      Yikes

    • Tanis Leach says:

      Granted still a week out so still possible for changes. Don’t like the chances though.

  6. JohnD says:

    ‘Seems like our “evolving” winter weather pattern is evolving slower than originally expected. I was waiting for pal Steve Pierce to name drop something compelling re the upstream outlook in his KOIN segment this evening. He did manage: “cooler by the end of this coming week.”
    Time will tell.

    • Mr Realist says:

      It’s a bust before beginning.

    • OLIVER WATSON says:

      Yeah the gfs was showing the goods yesterday then it pooped on us today. Looks like the euro is following suit

      • mike says:

        Seems like Oregon used to always have some interesting weather to talk about. I wonder what’s causing a series of unimpressive weather systems in recent years. I know that temperature differences clashing together is what fuels the excitement in our weather. Is it the number of contrails over the earth that is moderating the weather? It just seems so muted compared to years ago.

  7. Jason Hougak says:

    Manley Hit Springs, Alaska -65F. Nice to see Alaska having some cold weather again. You know somethings wrong when Alaskans are complaining it’s not cold enough.

  8. Jason Hougak says:

    https://radar.weather.gov/Conus/pacnorthwest_loop.php

    This has been the NWS link to the radar loop I’ve been using for years, not sure why it’s not working now?

  9. Jason Hougak says:

    The 06Z GFS shows the goods with cold air coming down from the NW and enough over water trajectory that it’ll pickup ample moisture. Looks like the fun will start around Jan. 4th. Dominating High Pressure looks to setup in the Pacific in the sweet spot keeping a conveyer belt of N/NW flow going.

  10. Winter Enthusiast says:

    I told my wife I didn’t want to go to Hawaii in January due to the fact that winter would show up…

  11. Ken in Wood Village says:

    The 00Z GFS just started showing a modified artic outbreak at the end of the run. The start of the New Year will start feeling like winter with the chance of snow starting around the 4th or 5th to some very low elevations. It could be a very interesting start to 2020. 🙂

  12. JohnD says:

    CPC looks to be in our court.
    Timing just beyond what TV Mets want to mention yet—understandably. We’ve played this game many times! 5% chance at a bullseye? Hopefully better than that!

    • Tanis Leach says:

      Mark has done 12 day trends in the past, maybe tonight? If so, word it as the odds are not good but it’s possible

  13. Jake in Gresham says:

    Eck, the 18z GFS is rather cocky on something occurring the 2nd week of January onward.

    It shows almost constant offshore flow starting around the 5th on Sunday with modified arctic air (so gorge effect) with a retrograde event bringing an impressive arctic front moving for the Yukon (-33 Celsius) by the 12th.

    Wait, I’ve seen this train ticket before.

  14. WEATHERDAN says:

    January looks colder than December. But cold enough for snow. Aye there’s the rub. Right now it looks marginal. But we seem to be moving in the right direction. I,d put the chances at 50/50. Not great but far better than December. In any case we have some hope. Peace.

  15. Jake in Gresham says:

    A everyone, went for hike this morning and thought to share some photos! I got my snow fix! There was some accumulation at the top area of the loop (at 1700ft or so):

    https://imgur.com/gallery/TvCIJVl

  16. Roland Derksen says:

    I saw some mixed showers (snow & rain) last night, but it didn’t last. In any event, the minimum temperature was 35F- too warm for anything to accumulate on the ground. Looks like January might offer some excitement?

    • OLIVER WATSON says:

      This is what I noticed. First the gfs shows something interesting then the euro catches on to it. Then the gfs starts going in a different direction then the euro starts catching up with it. I don’t know that the euro is King anymore. It’s now showing the cold weather the gfs was showing a couple of days ago. I think they are all on crack

      • Larry says:

        Quick model check. Every model has the night when snow is expected in the mid to low 30s. Even the GFS Ensemble (showing 6+ snow totals) has it 35 in the metro area. Point is things are not lining up right for snow.

        Your best bet is the Canadian model; currently showing no snow for metro, but tons up in the mountains.

        There IS a possibility we see things dip into the 20s on the 6th, Euro has the cold air from the east pushing a little more west, but I cant guarantee anything yet.

  17. Ken in Wood Village says:

    The 00Z Euro at hour 192 looks very interesting. 🙂

  18. W7ENK says:

    34 degrees in Milwaukie, and apparently there’s precip moving overhead? Nothing making it to the ground… yet. 🤔

  19. Mr Realist says:

    Everyone trusting the models 10 days out 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣

  20. Jason Hougak says:

    Anybody else noticing issues with trying to get the radar?
    Freezing up here in the foothills and would love to see some snow.

  21. W7ENK says:

    January 2004 redux?

    Stay tuned…

  22. Jake in Gresham says:

    I hope everyone had a good and happy Christmas. I know I did (way too much festive food!).

    I couldn’t help but sneak on here and read the posts. I’m really excited that SOMETHING is on the horizon. I mean I’m just happy the patterns have shifted and Winter is here.

    I was convinced that we might stay in a split flow all Winter with a terrible snow-pack because of trends we had in Fall.

  23. WEATHERDAN says:

    GFS Meteogram shows lots of cold and snow starting around the 6th of January. This has been an on and off theme for about a week now. At first it was 16 days out. Now it is about 10 days out. It is just beginning to enter the realm of believability. Maybe we just have a bit of Winter fun after all. We shall see. Happy New Year and go Ducks. Peace.

  24. Jason Hougak says:

    12Z GFS eye candy
    NW flow out of Gulf of Alaska arrives the New Year.

    • Ken in Wood Village says:

      I noticed that too. It shows close to about a foot of snow around the Portland area. It’s a lot of eye candy!! We just need to watch it for the next few days to see if this can be a trend.

      • JohnD says:

        Will be very interesting to see to what extent Mark makes mention of this is his post tonight.

      • Paul D says:

        It’ll disappear from the forecast. But for now it’ll pop up on the phone weather apps and freak everyone out 🙂

        • Joshua Lake Oswego says:

          The end of the operational run has artic air potential, but we all know it will end up east of the Rockies or certainly east of us.

  25. Winter Enthusiast says:

    I’m headed to Hawaii for Jan. 5- 12 as it looks like winter will show up during that time frame. The 12Z GFS total snow shows feet of snow in the Cascades. Nice accumulation in the Central Valley south and Cascade foothills and Coast Range as well.

    • Tanis Leach says:

      And I leave back to college on the 5th of January. That will be interesting.

    • Ken in Wood Village says:

      The 12/26/19 12Z GFS has just upped the WOW factor close to the end of the run. It’s showing close to a foot of snow close to the Portland area. But it’s so far out that it most likely will change. It’s a lot of eye candy in la la land. We’ll see what happens the next few days.

      One thing I am noticing in the Euro with the over all pattern, it’s setting up like the GFS with bringing colder air into the PNW in the extended forecast.

      It’s a long ways off but it’s something to watch for the next few days.

  26. Grizzly Bear says:

    Merry Christmas to bloggers back in PDX and surrounding area, still have a 1″ of snow on the ground and light flurries this morning. Hope you all get your winter wishes fulfilled in the New Year!

  27. Mr Realist says:

    Best Christmas gift ever, the long range looks mid to upper 40’s and a little wet. Valley snow is non existent.

    Happy Christmas and Merry New Year!!

  28. JohnD says:

    Merry Christmas fellow bloggers!
    Hoping 2020 brings lots of fun our way!

  29. WEATHERDAN says:

    GFS meteogram has a cold weather teaser for about Jan 7th. Heights dropping to 517. Probably nothing, but who knows. Merry Christmas to all and to all a good night. Peace.

    • Tanis Leach says:

      Euro seems to hint something too, also about 15% of the ensamble members at that time showing snow. At least wishcasting is back.

      Also Merry Christmas to all!

  30. Andrew says:

    models suggest some potential cold air way out around Jan. 6-8. not banking on anything but at least something to look at over next several days. merry christmas.

  31. Roland Derksen says:

    January is getting closer… sleepy weather is coming! 🙂

  32. Mr Realist says:

    I love the no snow effect this winter!!! Let’s hope it continues 👍🤞🤞

  33. Jason Hougak says:

    YAWN…🥱
    I do think it’s interesting watching the GFS run and Alaska is an ice box, 850mb temps in the -18C to -30C throughout Alaska. Hopefully this decides to make a plunge into the NW via NW flow at some point this winter.

    • Ken in Wood Village says:

      I’ve been seeing temps at 2-m around -50 degrees in Central Alaska and Western Canada on the Euro model. If we got a Northerly flow, this could come to the PNW. We’ll have to watch this closely.

      • Mr Realist says:

        🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣😘🤣🤣🤣 press refresh, feel free to play along

    • W7ENK says:

      In order for that bitter cold air to move our way, something would need to come along to displace it. Look for a ridge building in the Pacific to punch North into Central Alaska, that would do the trick. But it has to set up just right, along an axis running about 150W. Too far to the East, all that displaced cold air shunts down the back side of the Rockies, and we’re left with cold rain showers, or dry and mild. Too far to the West, and all that cold air dumps out over the ocean and modifies, leaving us with cold rain showers.

      Optimally, you’d also want to see a blocking ridge shove up the East Coast and into the Eastern Plains, Appalachia. That would keep the cold closer to us, filtering down into the Intermountain West, which would give us a backdoor shot through the Gorge, and hopes for an overrunning event.

      It’s really far more complex than that, but this gives you an idea of what signals you should look for beyond just the presence of cold air up North. Look up Rossby Waves.</a href> Ridges have to build in order to let troughs drop down. Cold air over Siberia or Alaska can’t drop South unless warm air in the subtropics moves out of its way, and likewise, warm subtropical air can’t punch North unless the cold polar air moves out of its way. It’s all connected, and everything moves together as a system. Look both upstream and downstream for hints at what may lie ahead for us, then you’ll get the big picture.

      • JohnD says:

        We all know that most of the time the requisite variables simply don’t line up favorably to deliver the goods. We keep reminding ourselves, however, that we are way overdue for a bonafide arctic event. So maybe we’ll get lucky this year!

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