Sunday Night Extra…A Big Freeze Coming?

     Steve Pierce here with a “special guest blog post” tonight. Had to swing by Fox 12 tonight to take care of some business. I guess I picked a good night to swing in. Why? By now you have all likely viewed the 0z GFS model run showing the Pacific Northwest going from “cool” to downright “frigid” this coming weekend. Not that this is a “lock” at this point in time, but the changes on tonight’s GFS are pretty dramatic, wouldn’t you say? Most obvious change is the colder 850mb temps, along with reinforcing shot of cold air again early next week. A quick check of historical data (stored mostly in my brain) leads me to think, if verified, that this would be the coldest air this early in the season since 1985. There is plenty of time for future model runs to change things one way or the other, but a trend to much colder sure looks better tonight than it did last night. Could it be the “09/10 Cycle” that I spoke of at the fall AMS meeting? Only time will tell! Stay tuned! ~ Steve Pierce – Oregon AMS

So what Steve really meant to say is “Mark allowed me to geek out all evening but is about to kick me out”.  Actually Steve behaved pretty well.

The image above is the 6-10 day 500mb. height deviation from normal.  It shows a huge 500mb height anomaly (positive) over SE Alaska.  That allows cold air to stream down the eastern side of the high as Steve has already pointed out.  The trend is definitely faster with the arrival of cold air on both the GFS and GEM (Canadian Model).  They also don’t have moisture of any kind for snow or rain through early next week.  The 12z ECMWF was much slower and not nearly as cold, but had plenty of moisture in here by Monday.

Of course it’s Sunday evening, and we’re talking about something 6 days away.  I won’t get really jazzed up about a big arctic outbreak until another 24 hours of cold on the GFS and the ECMWF needs to come around as well.  That’s why I didn’t go crazy with high temps in the upper 20s or 30.  I figure a forecast high of 35 on Sunday when all other forecasts are 45-50 is wild enough for now.  Wait…I was almost shoving Steve out the door but he just told me the 00z ECMWF would be out by 11pm.

Chief Meteorologist Mark Nelsen

346 Responses to Sunday Night Extra…A Big Freeze Coming?

  1. Aloha Rainshadow says:

    Something going on?
    You’d think there was an impending arctic blast?
    00z models are good so far with another biggie left in the hopper, due out in 45-50 mins.
    The 00z is cold but the cold got pushed back, again…
    the 00z ensembles are colder than the 18z for sure.
    The 00z GEM is wonderful…watch the 06z GFS tomorrow morning, if this looks like the 00z GEM, there is a very high likelyhood this will happen.
    And then there’s the Euro, it took baby steps toward an outbreak for us on the 12z, lets see if it comes in line tonight, if we see the Euro score it later, this could be money in the bag!! Even if it doesn’t, I just want to see improvement towards the other models, the dumb Euro has been crazy this episode!

  2. stevied (North Portland) says:

    KATU changed their 7-day. Still mild Sunday on theirs, but changed their hi on Monday to 38.

  3. Marc N.E. Orchards, WA says:

    KATU decided to join the party.

  4. stevied (North Portland) says:

    Man, next Monday would be quite cold according to 12z WRF-GFS if it panned out:

  5. Rob "Wrath" S.E. Portland says:

    0z GEM favors a strong arctic blast and looks like a snow event/storm for December 7th.

  6. Mixer Mixing Mixed Yevgeniy Mixed Mixing Mixer says:
    CHECK this out! day:10 who wins he low or A HUGE Arctic mass in BC?!!

  7. Boydo3 says:


  8. muxpux says:

    NWS seems really hesitant about this…or they are just taking the “normal” approach and waiting for medels to come into agreement before going ape. haha

  9. Marc N.E. Orchards, WA says:

    Did I miss something? Why are comments subject to approval by a moderator now? It seems to slow down the conversation.

  10. PeteyJ - Uptown Village Vancouver says:

    Looks cold to me!

  11. goducks09 (Oatfield, OR) says:

    At what point does a loud God-like voice come on the blog and order all of you vets to the Flab 5 compound? Thursday? Friday?

  12. stevied (North Portland) says:

    Yes, 00z does have transition event from hours 204-216, though a bit of lala land that far out in the models. Does indicate a possibility of an event. There would be some very cold air in the Columbia Basin if the 00z panned out just prior to this, so it would be at least a full-day event (few inches of snow, then a decent ice storm, then the thaw) in PDX and probably at least 2 days for Troutdale. IMO.

    Here’s Troutdale text output of 00z, down to -14c 850mb temps:

    Here’s The Dalles output, down to -17c, 509 thicknesses, and 10F surface temps at hr 180. That won’t go away quickly!

    • Rob "Wrath" S.E. Portland says:

      Good points. No it surely will not be removed quickly. Models will again likely overestimate how fast they want to/do remove the cold air in place especially below 6,000′

    • Anthony Bertolo - Gresham 500' says:

      The way I see it, if the 6 day turns out, in all likelihood we would have some sort of transition with systems brushing that close. As the moisture arrives, if any does within a couple days of the cold, the dewpoints are still way down enough to cause a transition event.

    • Rob "Wrath" S.E. Portland says:

      With continued easterlies keeping the cold air supplied in PDX metro… Yeah it bodes well for us.

    • stevied (North Portland) says:

      Yep, and remember evaporative cooling too. With all the DRY air plus east winds initially, temp will drop SEVERAL degrees at onset of precip and then fight its way back up to freezing, trying desperately to fend off the relentless Gorge influence. That will be Civil War II.

    • Mixer Mixing Mixed Yevgeniy Mixed Mixing Mixer says:

      DP: -1
      T: 32

      temp will be 15.5

  13. Rob "Wrath" S.E. Portland says:

    Another concern brewing.
    Check that out!
    Pressure drops to 982 in PDX.
    That’s very impressive.

    Big S winds after the 10th? Appears the SW jet is going to not only break through the ridge/cold air, but blast through strongly. Hmmm kind of reminds me of December 2007…. But this looks to have some real possible implications for the Willamette Valley too.

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