Briefly Dry, Then Big Cascade Snow

I’m blinded by the sun this morning…I know many of you have fog, but what a change from yesterday!  The precipitation has shifted south and we get a break until tonight.

A quick check-in since I’m headed to two schools this morning.  No new thoughts on low elevation snow Friday.  It’ll be close Friday morning, but still too warm for sticking snow in the metro area.  Then we dry out and turn chilly this weekend.  Models still keeping low pressure offshore on Saturday (fingers crossed), avoiding a possible encounter with the chilly east wind.

Check out our RPM snow total forecast for the next 72 hours!  That’s 2 ft. of new snow on Mt. Hood; almost all of it from Wednesday night through Friday morning.


Chief Meteorologist Mark Nelsen

126 Responses to Briefly Dry, Then Big Cascade Snow

  1. chris s says:

    So why exactly is this event being downplayed so much by mark. I realize its not gonna be anything more than maybe some snow in the air or a trace here in the valley, and certainly the general public should not be alerted because they will go crazy and prepare to be snowed in for a month, but it seems the mark of 10-15 years ago would have thrown a snowflake in the forecast for saturday and not have been so conservative. 🙂 just my 2 cents.

    • Jesse-Orchards says:


    • Mark Nelsen says:

      That’s actually a really good point (about the 7 Day only). I’ve got to admit, even just 5 years ago I would have put a flake in Friday. But two things going on: First, I think the public gets tired of “snow forecasts” that are really just a flake in the air in the end, and, it keeps the news people at bay a bit more if I don’t have flakes in there.

  2. Dave_in_Troutdale says:


    Good to hear from you again Snowman (although your predictions are an at best scenario even if everything flip flops). Try answering your phone once in awhile! KIO!!!

  3. Yevpolo1990 says:

    Yea…euro fixed it real well…

  4. Jesse-Orchards says:

    Hmmmm….the numbers on Mark’s latest 7-Day look a lot closer to my forecast from last night than his. 🙂

  5. David B says:

    I’m wondering if we might get some “surprise” flakes tomorrow morning in Seattle. Reason is that it’s clear right now, and the temperature is falling below freezing. If it keeps cooling down, and weak impulse comes in ahead of the main front (such showers are forecast), then there will be cold air at low levels and moisture.

    I remember this happened once about this time of year in Seattle in the mid-90s and surprised many people (including weather forecasters). Didn’t last long, of course, but it was the first snow of the season.

  6. Roman~Snow-Zone says:

    Oh yes, the best time of the year is now here. Looking forward for some intense storms as we approach the new year and afterwards… The current conditions right now are really nice with crisp clear skies and the cars are icing up. 32.9F currently, little to no breeze.

  7. Yevpolo1990 says:

    00z is similar to 18z because the low is in the same spot, it just doesnt have as much moisture with it.

  8. germantownsummit1000' says:



  9. W7ENK says:

    Socked in foggy here in Milwaukie… heh, it almost rhymes! Almost.

    No, it’s 39F and visibility is down around a quarter mile. And yet, NWS has failed to issue a Dense Fog Advisory once again.

    Poor form.

    • W7ENK says:

      I highly doubt it will freeze tonight though. 39F with a saturated airmass, leading edge of a warm front moving in overnight, I’d expect winds to start picking up from the South in a few hours, albeit light to begin with, but that fog will disappear right quick once that happens, and we’ll see temps jump up a few degrees. Best guess, 45-47 by sunrise?

      A couple things to keep in mind: Tomorrow’s warm front will completely erase the current cool airmass and wipe the slate clean, so to speak. It will basically reset the atmosphere, making the cold that follows relative to the passing system only. A warm front on a storm this strong, 60 wouldn’t surprise me tomorrow, though it would be a tad bit of a stretch. 57, maybe 58 is more likely. After the cold front passes, yes, the temperatures will drop quite quickly, and they’ll be comparable to right now, but probably not much colder, and certainly not dependent on the current setup.

      Now, once the cold front passes, the moisture clears out just about the same time the cold air behind it settles in – pretty quick – so it’s a race to see how much overlap there’ll be… typically none. Even at that, I still don’t think it will be cold enough at the surface to support snow, I just don’t see it in the cards.

      Just my thoughts on this foggy-Milwauggie e’nin. 🙂

    • Jesse-Orchards says:


      60 tomorrow? 😆

    • W7ENK says:

      Details son, DETAILS…

      What did I say, specifically?

      C’mon, you’re smarter than this, Jess!

    • Jesse-Orchards says:

      It’s unlikely to make it out of the low-mid 50s tomorrow. The upper air temps don’t support anything warmer than that. A storm can be strong as hell (this one looks pretty strong) but it can’t just produce warmth like that out of thin air. 850mb temps topping out at +5 and thicknesses in the upper 540s at the highest would get us nowhere near 60, even with uber mixing.

      So yes, DETAILS! 😉

    • Jesse-Orchards says:

      Also, you say temps will be comparable to now once the cold front passes. Completely different airmass than we are in right now, much colder. 850mb temps are just below 0c right now. On the latest GFS they are progged to be close to -9c on Friday. Thicknesses are hovering just below 540 at the moment, they are forecast to bottom out below 520dm behind the cold front. HUGE difference. I don’t understand people’s need to downplay this stuff, is it some sort of weenie self-defense mechanism?

    • pappoose in scappoose says:

      I didn’t know you were capable of this level of kindness Jesse. Hahaah!

    • W7ENK says:

      Weenie self-defense mechanism, or maybe just a memory for what usually happens in borderline situations. It may seem “pessimistic”, but it holds true more often than not, so I guess it’s a fine line.

      Just because you have a severe “cold bias” doesn’t automatically mean everyone that disagrees with you has a “warm bias”, Jesse. I like to think I have more of a “reality bias”. It’s really tempting at times to hold back the “I told you so”, but not once have I ACTUALLY dropped that bomb on the blog, unlike some.

    • W7ENK says:

      Besides, a system this large with a tropical connection brings in warmer air. I don’t thing 57-60 tomorrow is unreasonable, but I did say I was leaning toward the lower end of that. I said 60 wouldn’t surprise me.

    • Jesse-Orchards says:

      Learn to read the models then we’ll talk, W7. That’s obviously something you need to work on judging by this post.

    • Jesse-Orchards says:

      Well, all of these posts, really.

    • W7ENK says:

      Isn’t this what this whole blog thing is all about? Learning from each other?

      Oh, and FWIW, Mark get’s paid to make and modify his forecasts, you don’t… so quit yer b!tchin’.

    • Jesse-Orchards says:

      Absolutely, and I would be happy to help you.

      But it’s offputting when you start talking about what the weather is (or isn’t) going to do in such certain terms when you obviously haven’t even glanced at some of the upper air progs.

      And Mark and I have a contest, I am just keeping people updated. I also DO think it’s funny that I was given so much flack for my forecast last night, then tonight Mark’s forecast takes a big step towards mine.

    • W7ENK says:

      Well, no need to act all butt-hurt toward me, sweetheart.
      I didn’t give you any flack!

    • Mark Nelsen says:

      I only changed two temperatures (I think). What you saw earlier was Steph’s forecast. We keep having failures on the server that outputs it. Current is up now. And you two need to knock it off. Mainly you Jesse.

    • jesse no one cares if your numbers match mark, use some number crunching and find a hot girl or something 😛

  10. goducks09 says:

    Does anyone have anything to say about the 00z GFS? Is it that bad?

  11. Ben (Beaverton, 775 ft.) says:

    Did anyone check out the 00Z? The low is further offshore than the 18Z…no bueno.

    Good luck with that 4-6 in Seattle. What maps forecast that?

  12. Mat the Salmon Killer says:

    I think the snowman has the most outrageous forecast yet. Troutdale east that much snow? East winds are too dry and not enough precip. North Seattle too? I did need a good chuckle tonight. Thanks coaster

  13. Probably some snowflakes will fly at this location, not anticipating any substantial accumulation… I’ll report what I see

  14. Austin (Cornelius) says:

    LOVELY!!!!!!!!!!!!!!!!!!!!!! 🙂

  15. pappoose in scappoose says:

    Good to see you Josh, lets have some fun!

  16. W7ENK says:

    Oh Lordie, save us all! 😕

  17. pappoose in scappoose says:

    Calm before the storm at Timberline:

  18. stevied (North Portland) says:

    well, the 18z definitely made things more interesting and a closer call for snowflakes in PDX vs previous runs.

  19. PDX Weather Nut says:

    Anyone have any guesses as to how much rain PDX will get tomorrow? Sounds like quite a lot, much more than the usual drippy stuff …

  20. Garron says:

    Made a drive upto Larch Mtn., (OREGON) yesterday afternoon. Amazingly, still opened, but I imagine that it will be closed at mile 10 really soon!. There was no snow until mile #13, then a few inches became about 4-6″ by the time you reach the top. (around 3800-4000 ‘) It was briefly spitting snow while we were up there, real foggy, and a few people were snow boarding, and 4 x 4 ing.

  21. W7ENK says:

    Hey, what’s that bright shiney thing low in the SW sky??

    :gasp: *whispers* I think your Venus is showing!!! 😯

  22. W7ENK says:

    Just leaving the office…

    Oh my, it’s cold… and clear! (finally)

  23. Ryan (Walnut Grove) says:

    I think some folks are giving way too much credit to the east winds for this event. There is no cold dome built in the basin so no real cold air to draw on. East winds will dry us out but not cool us significantly.

    I also don’t think temps warmer than -7C @ 850mb can support snow unless you get a solid down pour to drag down the snow level to the surface.

    • Yes, east wind wont do anything for this event. Though, this event will help build up some cold air in the east, so that it can start helping future events.

    • gidrons says:

      If the east wind is dry enough it can cause evaporative cooling

    • Ryan (Walnut Grove) says:

      I dont think we will have enough moisture to make evaporative cooling work for us. If anything it’ll eat our moisture.

    • The big benefit of the east winds are the off shore component vs warmer on shore flow from that 50 deg bath tub off the coast. So that, by itself keeps us cooler by several degrees. In a marginal event (not saying this is one) the surface flow can make a big difference especially if the column of air above stays near freezing. We all know what a snow kill a SW wind is! Down here in the valley we don’t get the big east wind but rather a north wind. So when a low approaches from the SW and makes landfall to the south, we get our best shot at snow as the surface winds remains northerly.

    • Ryan (Walnut Grove) says:

      I will give you that. 🙂

  24. runrain says:

    Warning: Attack of the Killer Leaves!!

    With rainy and somewhat breezy conditions in PDX tomorrow and all the leaves on the ground and still in the trees (with the late fall) there are bound to be some new formed lakes around street gutters tomorrow!

  25. W7ENK says:

    Oooooh…. NWS is gett’n serious!

    It’s on, now!

  26. Jclack says:

    Not sure if anyone knows this or not… but when was the last time pdx had measurable snow before thanksgiving?

  27. Josh (Gresham) says:

    ‎18z GFS may be showing a pattern shift developing, that would make Saturday night into Sunday very interesting for the PDX metro. With the secondary low sliding much tighter down the coast, precip comes onshore late Saturday-Sunday, with the low developing an easterly flow, 850mb temps warm to -6c to -5c, but with the cold air in place, and the models tendency to underestimate the east wind abilty to cool the air, the atmosphere could support snow.
    -KTTD shows 0.06″ of moisture, which seems a bit underdone, but is possible with the drying east winds very close to the gorge
    – PDX shows 0.35″
    – HIO shows 0.33″

    FWIW, 12z GEM and NOGAPS showed this earlier

    • SnowedIn - North Plains says:

      Although what about the western side of the metro? The east wind generally doesn’t affect us much over here, does it?

      North Plains is normally one of the coldest spots in the metro that is a lower elevation, so even without an east wind here, we get some of the colder air pooling up against the coast range. What are your thoughts?

  28. Oh boy, 18Z pulls the low closer to the coast line and throws in some moisture. I see an emotional roller coaster on the blog coming soon. I’m offering weather therapy for only $100 an hour. Book now, rates subject to change depending on the track of the low.

    • pappoose in scappoose says:

      Hahaah! I hope you go broke, but in this country, odds are you’ll become a very wealthy fellow.

    • Emily Waldman says:

      Oh yeah baby! I don’t get weather emotionally involved so I won’t need the therapy! I will be taking care of those getting their shopping/retail therapy or Christmas shopping done these next five days! I have front & four wheel drive so no worries! 

  29. Yevpolo1990 says:

    NOGAPS and GEM pull the low to Newport and show the low making landfall….18z gfs moves low way closer to the coast, hugging precip along it as welll with more moisture than 12z, possible trend?

  30. W7ENK says:

    Hey, just in case no one else had mentioned it yet, the 18z shows the low coming down closer to the coast on Friday! 😆

    Problem is, it’s a fairly weak low, so it probably won’t be pulling much if any moisture along with it, more likely just a bunch of high- and mid-level clouds with significantly higher accumulations of strong to severe disappointment. 😦

    • Josh (Gresham) says:

      The second low on saturday is more interesting

    • Josh (Gresham) says:

      Well, late saturday into sunday overnight

    • If the low did track as it shows in the 12z euro, there likely would be some frozen precip. It would just be light.

      18z GFS is trending toward the euro.

      There’s a chance of a taste of winter. I would advise folks to not get too excited for this “event” as, even if there was some snow, there’d be nothing to show for it.

      The part to be excited about is that the last time we flirted with snow this early, was the widely chosen analog for this year, 2008. That would be nice to have again.

    • NR says:

      It needs to be a weak low or it pulls in warm advection and the existing cold air will go away.

    • chris s says:

      Anthony, dont forget we had minor snow accumulations pretty much same time last year within a couple days of when this event could happen, and I dont recall anything special happening Nov of 08 ????

    • W7ENK says:

      @NR, true… It’s a delicate balance.

    • My memory could be serving me badly, but I though I remembered multiple brushes with snow starting mid-late November all the way through the big event the week before Christmas. I haven’t looked at the observational data to validate or discount that though.

    • chris s says:

      Anthony Nov was pretty mild overall, at least down here in salem. I do remember a nov where we did flirt with snow a couple times besides last year but i think it was quite a ways back, but not sure about that. 🙂

    • Timmy_Supercell (Klamath Falls @ 4200') says:

      Yes November of 2008 was mainly a messy rainy month with highs in the 50’s and lows in the 40’a and such. Snow began I think around the 10th or 11th of December…. Not sure exactly but definitely around that time period. Sad it didn’t last long either, when January 1st came, it turned into what I recall, one very very wet January. I enjoyed how the jet stream acted though, lots of energetic systems training through the PNW.

    • Emily Waldman says:

      We had a freak snow event in Cowlitz County Nov. 2010! The kids had 2-1/2 snow days the week of Thanksgiving! Any thoughts of a repeat this year?

  31. Cold in Alaska:

    Fairbanks has a high so far today of -14. Their average is about 10. So 24 below average. If that were here we would see a sub-30 high temp.

  32. The 18z shows the low much closer as it moves into Oregon vs. hanging off of the coast and heading into Cali.

  33. The sun is FINALLY starting to break through. Up to 41.

  34. Yevpolo1990 says:

    18z nam has the initial low (friday) pulling the second low behind it. It is a bit more west, a bit closer to the coast.

    • NR says:

      18z gfs paints a small amount of qpf west of the Cascades Saturday morning. The low is much closer to the coast than prior runs, and matches up well with the Canadian model. Through 96 hr

    • Josh (Gresham) says:

      18z pulls that low much closer to the coast hours 90-102. This would mean alot more moisture for PDX

  35. Officeman says:

    How much rain are we looking at in the valley in the next 24 hours? 1″? .5″?

  36. W7ENK says:

    Looks like Longview is the only sea-level-ish area that might see sticking snow? Why’s that familiar? 😦

    I still think 1,000 to 1,500 feet is going to be about it. It would not surprise me in the least if the VAST majority of the lowlands bottoms out at 37F and gets only chunky rain at best – before the moisture clears out, then the temps will drop, and Friday night could be an icy mess in spots, what with all the wet roads. Even so, lows in the mid-upper 20s, highs low-mid 40s, and with that I agree with your previous statement Mark, “not a ‘wrap your pipes’ sort of freeze”, but close enough, still not a bad idea to just get it taken care of.

    We’ll see…

    • W7ENK says:

      ↑ Never mind those, I simply forgot to click “Notify…” 😳

    • Tyler Mode says:

      It’s because the model doesn’t recognize the narrower valley up there. It still sees it as higher than it is.

    • W7ENK says:

      Yeah, those 12km grid points just aren’t high enough resolution, I suppose. It’s really misleading! I can see how some people unfortunately get all worked up and excited over it when taken at face value.

    • Mark Nelsen says:

      That’s correct, our 12km RPM probably sees Longview as about 1,000′ ridge between the Cascades and Coast Range. I would think the 4km can see it though.

    • Emily Waldman says:

      Well Mark, snow or no snow in Longview? I live 400 ft up! I would be happy with flurries in the air! 

  37. pappoose in scappoose says:

    Snuck a new post in.
    Like the pic on this one.

    • Emily Waldman says:

      So papoose! What’s the word’? I see 2 inches of snow for our areas!

    • I’d like to wish a couple inches in here! I think anything’s possible, secondary to the models obvious confusion. With a tropical connection and the “struggle with this fast-moving pattern,” I suspect the models are about to blow a fuse. Hahaah! Looking forward to the GOLU model taking over.

    • pappoose in scappoose says:

      I’m putting studded tires on a couple vehicles today. Pretty much guarantees a pineapple express. Or maybe a wind event?

    • W7ENK says:

      I need to dig out my tires, they’re all the way against the far back wall of my storage! I guess that’s what I get for moving into my new place in June… 😳

      BTW – Next time you need to purchase snow tires, get the studless ones. Honestly, they work just as good on snow and ice as studs (if not better), and they don’t grind ruts into the asphalt.

      I’ve been running studless snow tires since 2001/2002, all through my time spent “surviving” at 4,400 feet down in Klamabama, and I swear by them! They’re amazing what they can do, and on a number of occasions I’ve had opportunity to drive around some idiot that can’t seem to make a studded 4×4 work up an icy moderate hill! 😆

    • pappoose in scappoose says:

      I’ve heard that W7. Just force of habit I guess.

    • W7ENK says:

      You can’t teach an old habit new tricks? No… Old dogs are hard to break?… Gahhh! it’s something like that. o_O

      Regardless, I like them, and everyone I’ve ever given a “demonstration” to (AKA braffing my car around on the snow and ice, deliberately slamming on the breaks and jerking the wheel, generally having fun!) has been impressed, even the most hard core (nothing works as well as actual metal spikes!) believers! 🙂

      Actually, here you go:

      Done safely in the wide open parking lot at White River beside Hwy 35 on Mt. Hood, studless snow tires all the way around, yanking on the E-brake deliberately trying to lose control, at one point I slammed on the breaks headed down hill at 30 mph and the car stopped about as quickly as it would on wet pavement.

      This is the best demonstration I can offer via the InterFacePlusTubes.


    • W7ENK says:

      Never mind my sister’s panic-stricken screams, she just doesn’t know how to have fun! Plus, she’d been living down in Florida for about 5 years at this point, so she’d forgotten what snow and ice were. 😆

      Mark, you may remember her from her internship with you and Jim at KOIN, waaaaaay back in the day? I hope she didn’t scream like this in the studio! 😀

    • W7ENK says:

      *breaks, brakes… whatever.

    • pappoose in scappoose says:

      Hahaah! Looks like fun W7. Have you ever seen motorcycles racing on ice with metal spiked tires? That has to be about as good as it gets! (wear bulletproof vests no doubt)

    • W7ENK says:

      That does sound exciting, though perhaps painful to watch at times, I’d imagine!

  38. NR says:

    What’s the consensus opinion of the Canadian model? It’s still bringing the low into Newport on Saturday afternoon.

    • O, that could be a game changer…. Would the air be cold enough flowing through the Gorge though.

    • NR says:

      That’s one problem, it’s not very cold east or west of the cascades.. 850mb temps start to climb ahead of it and are nearly 0c over Portland.
      It’s a similar pattern to all other models, but the split happens as it comes onshore instead of 150 miles offshore. The next EC run will be interesting. Those little differences have a huge effect.

    • Yep exactly right. I just looked at the WRF too and it is less than impressive. The PDX-DLS gradient is weak and I see no surge into the Columbia Basin either. Oh well there will be a huge pool of bitter air in Alaska/Yukon so if we get back into ridging early December might be incredible…

    • NR says:

      Agreed, as much as we’d like to wishcast this one, the real frigid air is heading east as usual and the Columbia Basin will be cold but not !COLD!.
      Latest Euro has the low even farther off the coast.

    • Josh (Gresham) says:

      Yeah GEM is interesting with the positioning of the low, interested to see if any other models pick up on that

  39. Ken ( S. Salem 500ft.) says:

    Should be a fun few days of model riding. I think we might be in for a treat.

  40. Ken ( S. Salem 500 ft.) says:

    Should be a fun few days of model riding. I think we might be in for a treat.

  41. I for one will be happy to see a dusting Saturday.

  42. umpire says:

    Ha, First! The fog is quite thick downtown, will be interesting to see when/if it finally breaks down and we get some sun. I actually hope this weekend stays dry, even if chilly, as I need to get one more weekend of leaf raking (the City of Portland now calls it “leaf harvesting” 🙂 ), so the cold, dry, sunny days would be ideal.

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