Drier Than Normal Next 7 Days, But Turning COLD!

6pm Wednesday…

Today was an amazingly boring weather day, with just areas of low clouds/fog in the valley and some sunshine central/east metro area.  Not much happens tonight, Thursday, Friday, or the 1st half of Saturday.  Take a look at the 3 day rain forecast from our RPM:


Yes, pretty light stuff with a weak cold front that comes through Thursday night.  That means the daylight hours tomorrow and Friday should be dry.  Saturday morning will be frosty and cold with temps below freezing under a cool airmass.

Things start to get interesting just about the time all you folks start partying New Year’s Eve (2nd half of Saturday).  The upper-level flow begins coming in from the north, and a disturbance is dropping south through British Columbia.  Take a look at the 500mb chart for 4am Sunday:


You see the disturbance carving out an upper-level trough right over us.  Air is flowing from the arctic south straight into the Pacific Northwest.  At the surface, there is a surface low pressure area developing over southern British Columbia.  This map is right at 1am…one hour into the New Year.  Note two things:  first, the airmass is quite chilly, snow could fall even below 1,000′ in this pattern.  The 2nd, a tremendous westerly to southwesterly flow is on west of the Cascades due to that developing low.  That gusty mixing wind will likely keep sticking snow above 1,000′.


There will be plenty of showers, with the ECMWF showing the potential for 8-15″ snow in the Cascades, that’s due to a very strong westerly wind between 2,000-6,000′.  Perfect for orographic lift…the west slopes of the Cascades will get pounding by heavy precipitation for about 12 hours from late Saturday through late morning Sunday.


By 7pm Sunday the surface low pressure center is weakening and dropping south over Western Oregon.  At this time the surface wind is turning north and northeast as very cold (and very dry!) arctic air invades the Pacific Northwest:


The WRF-GFS is even more interesting, check out the 24 hour snow total ending Sunday PM:


Notice how far west the snow is pushed down into the foothills and even far eastern Willamette Valley!  That’s due to the strong westerly flow pushing up against the west slopes of the Cascades.  It’s only noticeable if you regularly look at these maps.  This says significant snow could fall even down to or below 1,000′ on the east side of the Willamette Valley.  For sure the hills will get a dusting, but in this pattern I think significant snow down on the valley floor is unlikely.  But if you live in Sandy, Estacada, Sublimity, Mill City, Sweet Home etc…?  You could see a few inches of snow on the ground by Sunday AM or midday.  After that ALL models agree we dry out quickly as a the dry arctic airmass moves in.

To summarize:

  1. A significant snowfall is unlikely in the western valleys and Portland metro area New Year’s Eve & Day
  2. But we could see a dusting of snow just about anywhere early New Year’s Day, most likely that’ll happen on the hills
  3. Roads may get covered with snow above 500′ or so near/in the Cascade Foothills by New Year’s Morning.
  4. Coast Range roads will likely be snowy/icy later Saturday night through Sunday.
  5. There is relatively good model agreement on the general progress of these weather events Saturday/Sunday

Beyond Sunday…

Models are in excellent agreement that we’re into a cold and dry pattern for at least 3 days…Monday/Tuesday/Wednesday.  How cold?  Now at least the GFS has come around to the colder ECMWF/GEM models, showing 850mb temps dropping down to the -12 to -13 range Monday night and Tuesday with offshore easterly flow.  These numbers are in the same category as the December 2009 and December 2013 cold spells.  Not a massive 1990-style “Mr. Cold Miser Has Arrived” blast, but definitely an outbreak of arctic air.  So prepare for the coldest airmass we’ve seen in 3 years.  It’s going to be in place over us much of next week.  That means wrap pipes and protect your pets/livestock/animals.  High temps will likely only get up to around 30 degrees even with full sunshine.  That’s assuming we get little/no snow cover on the ground.  If some part of the Willamette Valley ends up with 2″ or so (not expected for now), temperatures would be a good 5+ degrees colder.  East wind will also be blowing through the Gorge, although it doesn’t appear to be a real strong wind for now.  Lows should reach down into the 10-15 degree range, even here in Portland.  It’s about time!

Our forecast looks like this for lows:


Note the lowest temperature we’ve seen each winter from my OMSI presentation back in October.  During the last December arctic blast we saw a few upper single digits in the metro area and then lower teens.  That’s why I have that 12 degree forecast, especially with the east wind not looking too strong.


There is very good agreement on this second part of the forecast this next week…the cold part.  Check out the ECMWF ensemble chart from this morning:


Look at all those lines very close together through next Thursday, the 5th.  Then things break down, but the trend is to add some moisture back into the forecast as the pattern stays cold.  Yes, we could be looking at some sort of snow/ice event the end of next week.  That’s still 8-10 days away though…

Chief Meteorologist Mark Nelsen




76 Responses to Drier Than Normal Next 7 Days, But Turning COLD!

  1. Sapo says:

    Well tonight has shown us that models are fairly clueless past 7 days at the moment…Weirdest pattern progression in a couple days on the 00z GFS/Euro, much different than other runs. Euro does give us 2-4″ Friday-Sunday timeframe (Jan 6-8), but weird 500mb progression. GEM is pretty different. WRF took away precip on Thursday, really most of this besides the cold through Thurs/Fri is up in the air at this point.

    We probably won’t know too much about our snow chances for 3 or 4 days at least.

  2. Joe says:

    Can anyone give me a good link for checking WRF model? Or does anyone know if you can view it on pivotalweather.com

  3. Sapo says:

    Just get back to weather everyone…

  4. GTS1K' says:

    Hey, whatever makes your poodle bark, Elaine.

    Don’t worry – be happy!

    I’m happy to engage trolls – even the repetitive ones.

    Running low on snark, are we?

  5. GTS1K' says:

    Well then Alan, my good man (or woman), why visit this blog?

    Oh, I think I know.

    P.S. Don’t you wish (or, would it be wis) that the blog had an edit function?

    P.P.S. I’ll be here all week – be sure to tip your waitress….

  6. Epic Portland ice/snow storm January 14th-15th all but guaranteed! Three necessary ingredients are coming together perfectly. Massive cold pool east of the Cascades, moisture from the west and my non-refundable Bahama cruise.

  7. kcteach says:

    Anyone have info about Larch Mtn (Oregon?) It’s a great place to drive to the gate, which is closed in winter, and take the dogs for a walk. Wondering if anyone knows the conditions there right now. Thanks.

    • Dave in SW PDX (235') says:

      Mark might know since he lives in that area, but there has to be at least several feet of snow at the top of Larch Mountain (4050′) right now. The nearby North Fork SNOTEL site at 3060′ is reporting a 41″ snow depth today; South Fork at 2690′ has 19″. Not sure what the elevation is at the snow gate, though.

      Here’s the link for the Oregon SNOTEL map:


    • sds says:

      The gate is around 3000 ft.

    • WWM says:

      I can tell you there is a lot of snow, if you don’t have a good 4×4 don’t even attempt. I live down the road from the gate around the 6 mile marker and we still have snow on the ground here and that’s 2000 ft. level, its a lot higher at the gate. Just don’t get stuck, locals don’t take well to folks trying to come up their driveway at 2 am wanting help. It is a beautiful view on a clear day though.

  8. buffedman says:

    1949-1950 redux,a big year for Pacific Northwest winter weather

  9. High Desert Mat says:

    Thanks for the great post Mark, just curious though, what kind of weather do u want? Do u want this to come to fruition or do u want it to be partly cloudy and 40 due to you’d be working twice as much?

  10. GTS1K' says:

    I mean, it’s not as if HAWKEYES23 isn’t the late, unlamented, NATHAN PLACE, after all…..

  11. Sapo says:

    12z euro was possibly the coldest run yet, 850s bottoming out at about -15c which is very impressive. 12z GEM and GFS were pretty good too, GEM is somewhat strange after day 5/6 but gives us a lot of moisture.

    One thing that models can agree on is some kind of precip on Thursday night/Friday (Jan 5/6) but amounts are still up in the air. GEM is pretty bullish with it, Euro is very dry with light flurries/dusting, GFS is off and on, WRF looks possible for 1-2″. Should see at least a dusting at this point.

    Our real potential for a snowstorm is Jan 7-9th or 10th timeframe, Euro ensembles looking really good and 26 of 51 show 6″+ by the end of the run. No specifics yet but looks snowy

    • Jake-(Gresham) says:

      Sapo, I agree on all points. The only thing I don’t agree with on is the slight disagreement of the models on the severity of the cold. I believe that takes more noting of.

      We both know it’s really tough for the cold to get past the Rockies, down the East side of Washington, into the Columbia basin, and then over the Cascades (not just through the gorge for those new here) if we want a historical cold arctic blast.

      I’ve noted Mark is saying it’s going to be the coldest it’s been in 3 years. I believe the disagreement among models is the devil in the details here. I’ve also noted that the cold got pushed back just ever so slightly to the 3rd and morning of the 4th. Models do a poor job of catching this and that’s all we’re going to get.
      So that says to me that we’re in a little trouble. The cold will get here but I don’t think it will break numbers.

      I know you follow / know this I just feel it worth mentioning because I’m not seeing the cold to provide significant snowfall down the road of 6”+. Not saying this arctic air will be a bust.
      Just that it will not be anything historical and that the weather systems later on may only give us an icy and windy mess by the time any moisture arrives. Granted, it’s tough for air to moderate (warm up) this time of year but the weather systems are way down the model range.

      Just my thoughts / 2 cents.

    • Jake-(Gresham) says:

      I.e. I guess you could say I was hoping the models would line up like a royal flush like in 2008. The agreement was for 8 days straight. Just not seeing that here.

      The consolidation is a bit of a tug of war among kindergartners. Not a big one but still notable. That’s all we need however to only to have an arctic blast that’s dry with nothing to speak of. The next 24hr model runs will be huge IMO. Which is what I said yesterday, lol!

      I guess I was taken prisoner on the train…. I hate you all…

    • Sapo says:

      Yeah I agree with you that most significant moisture is past day 7/8 on the models, and that’s pretty worrisome..However, as we’ve seen time and time again, moisture can come out of nowhere just 3-4 days out so we can’t say for sure that we won’t see significant snow in the next 7 days.

      That weak system approaching from the NW on Thursday is something to keep an eye out for, sometimes we can get more precip than expected with those…GFS has trended drier the past couple runs but the 12z WRF is wet and so is the GEM.

      Ensembles look good so I think we’ll see a snow event in the next 15 days, question is when

    • JohnD says:

      I think it is interesting too that we mustered 2–not 1 but TWO–low elevation snow events already this season–even amid marginal conditions. I cannot believe that–going into a fairly entrenched pattern that is coming up–that we will not get the snow goods at some point!

    • Jake-(Gresham) says:

      Sapo, thanks for the conversation and dialogue. I agree 100% and with JohnD you putting it that way makes this all the more of a ride!

      I don’t think we’ll be able to sustain ourselves if this goes full blown snowmageddon. At least I won’t be able too. The last few days driving out to Damascus for work and seeing Mt. Hood looming overhead, glistening. Haven’t seen that in some time. Solid reminder of why I live here. Awesomeness.

    • Sapo says:

      00z GFS/GEM pretty much done, GFS was definitely colder with some small improvements through day 8, then it turned crappy…But it’s more important to focus on improvements in the more believable range, long term changes all the time. Not much moisture with the GFS and when we do get it south winds moderate us quick, but like I mentioned snow is harder to forecast until a day or two out.

      Still potential for snow on Thursday and GEM looks pretty solid, 9-10″ of snow by the end of the run. Onto 00z euro! 00z WRF is running now and I’m interested to see if it give us precip on Thursday.

  12. pappoose in scappoose says:

    National Weather Service Portland Oregon
    916 AM PST Thu Dec 29 2016

    Now, comes the fun part. Next front will arrive on Saturday. But
    rather than coming off the Pacific, this front will be arriving from
    the north. This front will spread clouds across the region on Sat,
    with light rain arriving later in the afternoon. Main surface low
    will slide along the British Columbia coast, then into the Puget
    Sound area later Sat night, with an arctic front just off the British
    Columbia coast to Puget Sound then across eastern Washington. Behind this front, much colder air. This will be the air that brings snow to the lowlands later possibly as early as Saturday night. /Rockey

    • GTS1K' says:

      Music to my ears….

      Thanks. ‘Poose.

    • pappoose in scappoose says:

      Now comes the fun part!

    • boydo3 N Albany says:

      Certainly looks hopeful but not much moisture left over as the cold air swoops in. Going to be fun watching the temps drop.
      Take your hoses off the outside spigot if you haven’t already done it!

    • Sapo says:

      Yeah everyone SHOULD see snow in the air…12z GFS says we could switch over as early as Saturday night with temps 34/35 and dewpoints around freezing. We could get to freezing by 2-4 AM Sunday morning with about .1″ of precip left, so i wouldn’t rule out a widespread dusting or half inch..But our real chances for snow come late next week

    • pappoose in scappoose says:

      Getting the cold is the hard part. Looks to be a lock.

      Moisture is harder to predict. The low dropping down Saturday/Sunday, could easily exceed projections.

      No way to know til the last run of the GOLU model!

  13. GTS1K' says:

    Dense freezing fog and 32 – Hurry up weekend…

  14. Sapo says:

    00z euro looks nice

  15. Jason Hougak says:

    00Z GFS looks good through the run too for cold weather. Drier first half and more precipitation in second half. The snowfall loop shows a snow covered Northwest for sure by the end of the run.

    • Diana F. says:

      I had watched that loop over and over, and at first I couldn’t quite fathom
      what I was seeing, so much BLUE everywhere…..so then it became mindless entertainment, I mean the perfect backdrop for my daily wishcast! “Make it so”, say all the ❄️ loving weather geeks on Mark’s Blog, in complete and utter unison!

  16. Scooter says:

    Just tried to watch the weather update on Mark’s 8 O’clock news but geese what a bunch of weird social media crap that is so prevalent these days passing as news stories…..school fire somewhere…… cat with three toes…… on and on and on…. I don’t know how he can work at one of these news outlets…. probably for the money just like the majority of society that has become so greed driven. We are living in a fake-a-loo society and I am saddened that most of you buy in, hook-line-and sinker. Wish you and your children the best in the world you are creating.

  17. Jason Hougak says:

    Sorry Mark but I wouldn’t call today boring in the slightest. To start it was slick with black ice. The sunrise and seeing Mt. Hood was awesome. Crossing the Willamette River on 205 at Oregon City looked like we were driving on clouds. The weather had foggy patches but also breaks. But the best part was driving home and seeing an alpenglow sunset on Mt. Hood. It’s times like that which make being an Oregonian amazing! 👍🏼 👍🏼
    The coldest it’s been at my house was 4F when Eugene reached -10F. We had no snow on the ground here at that time, in fact that was the time I built my snow machine so we could sled with the kids in the back yard. I love seeing the snowfall potential. About 45 minutes til the 00Z GFS…

    • Jake-(Gresham) says:

      I’m going to make some tea for this one.

    • boydo3 N Albany says:

      hmm…type of tea? 😉

    • marinersfan85 says:

      I left Newberg headed for Tillamook at 6am this morning. I’ve never had a more white knuckle drive ever. Even during any snow event we’ve had.

      The fog was thicker than ive seen it and hwy 6 was frozen solid for about 10 miles. Looked to be 6 inches on the ground at the summit.

    • Diana F. says:

      I feel a bit shallow after reading your articulate prose, but I must admit that I too thought it was a bit of a let-down day from a weather perspective. Felt like nothing was really going on in that department. But I hear ya Jason! I think it came from more of a “wow would I love to see some interactive winter weather right about now” and certainly not a “damn today sucked and we live on a horrid planet ” kind of way. I am in awe of Mother Nature on a daily basis….from the sound of a breeze, to the aroma of springtime, to the sound of an 8 year old’s screams as she rides her new electric Vespa-styled scooter for the first time! It’s ALL good!

    • Diana F. says:

      Wow marinersfan85, that does sound scary! Glad you made it!! Continues to surprise me how much our area has such a wide range of conditions. Be safe!

  18. Paul D says:

    Bring it on!

  19. Brian Schmit says:

    Come join in this dynamic and fun weather group on facebook. Currently 1463 weather geeks in one forum with 24/7 weather event coverage by the local experts. To join click below link:


  20. JohnD says:

    Was hoping that Mark’s rendition would have been a bit more bullish. Still, we get what we get and are glad for it. And we’ll see in the long run.

  21. pgiorgio says:

    Is there a way to block seeing scooter. His troll comments are annoying and seeing his name is even annoying

  22. Lurkyloo says:

    Oh. Damn. Time to get more firewood.

  23. Scooter says:

    Gloom and boring….quite the technical terms coming from our ‘fearless leader’ looks like he too is smitten by the constant need for titillation, I thought the weather today was quite grand and exciting for the three mile walk with the dog down at the Clackamas River, only met one person today and that was a fisherman with smiles ear to ear and yet no fish in his bag. Sunny and beautiful with an abundance of wildlife greeting us at every turn…..not surprised I did not see any of you constant complainers down there today. Then a beautiful afternoon working outside on the farm…..My only wish this Holiday season is you all could have enjoyed the outdoors as much as I do…….and maybe give up some of your tech pacifiers and park that “Bro truck” or “Jewelry box” for just a day or two…..there is so much more to experience than what “Madison Avenue” has hooked you’ll on!

    • Jake-(Gresham) says:

      I welcome you in joining the group on rooting for the cold to make it over the Rockies. 😛

      I’d require at least a kombucha after that.

    • Lurkyloo says:

      I’d require about 4 shots of whiskey after that — and I don’t drink whiskey. Mama bear must’ve been full, otherwise dude would’ve gone the way of Grizzley Man.

    • Lurkyloo says:

      Oops, I meant “grizzly.”

    • Jake-(Gresham) says:

      My sentiments exactly.

    • GTS1K' says:

      My only wish is that, for this (why did you capitalize “holiday”) season, you would go up the chimney and return to whatever hole you crawled out of.

      I’m reasonably certain that your “hole” is in Barton, Farmer Ted.
      Oddly appropriate…

  24. Sandi (Wilsonville) says:

    Thank you, Mark! Nice post!

  25. Andrew says:

    Thanks Mark!

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