Cold Air Arrives Monday

Just 3 days!  In the entire month of December we’ve only seen 3 days with temperatures below normal…all at the beginning of the month.  Since that time it has been very mild.  In fact no freezing here in Portland for over 3 weeks!


Tonight we’ll stay mild with temps above freezing and just a few scattered (rain) showers.  Then cold air starts pouring into the Pacific Northwest as skies clear out tomorrow.  I haven’t been expecting any snow below about 1,500′ west of the Cascades because we dry out at the same time the cold air arrives.  That doesn’t mean you couldn’t see snowflakes mixed in with early morning showers, but that’s unlikely too.

The intensity of the cold air looks about the same as mentioned in the previous post.  This is not a “mega” blast of either east wind or cold air that we COULD see this time of the year.  High temperatures in the low-mid 30s under sunny skies are sure chilly, but nothing like 20s!  As for east wind, just the usual gusty easterlies tomorrow and Tuesday, then mainly calm Wednesday/Thursday.  Models only suggest 4-6 millibars easterly gradient through the Gorge, much tamer than the Veterans Day east wind event.  In fact check out the current WRF-GFS cross section:

vs. the November version…that was a wild forecast and it verified!  kpdx-th1

With calming wind and a cold/dry airmass, we could see the coldest temperatures so far this season either Wednesday or Thursday morning.  23 is the coldest temperature we’ve seen so far in Portland.

Beyond that, models have gone back to a ridging/split flow setup along the West Coast again for next weekend and beyond.  So it’s especially good that we’ve seen some great snow totals this weekend in the Cascades.  What an improvement in just 7-8 days!



Chief Meteorologist Mark Nelsen

37 Responses to Cold Air Arrives Monday

  1. IceCold says:

    Mark, how much snow did you get up at your place last night?

  2. jimbo says:

    I appreciate all the varied weather. Foothills look awesome today!

  3. Garron near Washington square says:

    Dew point has dropped from upper 30’s to low 30’s since last hour, and I’ve had a couple of 15 MPH gusts.

  4. This little cold blast was always going to be a bit on the meh side aside from some stout east winds and colder than average temps. Nothing special to look at through mid-January for the moment.

  5. W7ENK says:

    It was 44 and raining when I left the house this morning, 48 at midnight, blowing away today’s forecast high temperature by nearly 10 degrees.

    At this point, Mark may need to change the title of this post to read “Cold Air Arrives Tuesday”


    • David B. says:

      Yeah, the arctic air is really taking its time with this one. Hope, BC didn’t even drop to the freezing mark until this morning.

    • W7ENK says:

      I anticipate this arctic front will likely stall out North of the Columbia River, but somehow magically wrap around and impact the LA Basin by moving up out of Mexico over New Years.

      Yeah… weirder things have happened.

    • Mark Nelsen says:

      Arctic front went through once the wind switched this morning. Colder air just gradually filters in the next 24 hours

    • Dewpoint dropped 10 degrees in 1 hour. Definitely seems like the colder air mass has arrived.

    • W7ENK says:

      Drier air mass, certainly, but I would hardly call this “arctic” by any means. Usually I’d expect to see a stark drop in temperatures along with. We’ll see by tonight, but things aren’t shaping up well for today. Rather boring so far, but hey, the sun is shining! 😀

    • GTS1K' says:

      It’s the “warmest” part of the day on a sunny day. Even on 12/29 that will affect the temp. It has stagnated since about 11 AM depending on location – so what’s causing that if not cold air (which is what the title of Mark’s post actually says)? Arctic in origin it may be, late it may be, but…. it’s arriving.

    • PurpleHaze says:

      You’re link only takes me to the top of this page.

    • Garron near Washington square says:

      Interesting that the temp from midnight to now up there has only budged a degree from 36 to 35. At least the dew points are starting to drop more aggressively from 22 degrees/F to 14 since midnight. Should not be a shock that the arctic air is taking its sweet time missing the moisture, but always disappointing to me after all these years of hoping that we’d get an Ana front during one of these episodes…..

  6. MasterNate says:

    Well, the models are disgusting! Dry and Splitty! See you all ina week or so.

    • PurpleHaze says:

      Not surprised in the slightest. As long as whatever telecommunications is still out therethe NPAC high stays!

      We are going to continue getting nothing but “Dry and Splitty” as you put it. This solution was considered the worst run naught but just a few days ago and it’s becoming the reality.

      I blame climate change as we are in a new regime though the part of it being man made is up in the air still. Better get use to less freezing weather and hotter summers.

    • MasterNate says:


    • Andrew (Beaverton) says:

      The earth warms and it cools, just like it has for millions of years. Man hasnt changed anything.

    • WX Ninja says:

      Andrew: I’ve wondered for years if the amount of concrete and asphalt, as well as new buildings, has increased the over night temps. We have all felt the warm concrete or asphalt under our feet at night after a hot summer day. Does it simply slow down the rate of cooling or does it indeed keep the night time temp up? I’m not saying I agree with man caused global warming/climate change, just curious what affect concrete/asphalt have, if any, on our temps.

    • Andrew (Beaverton) says:

      Actually, i do believe that major cities can be warmer “due to man” based on the heat generated by exactly what your refering too. Cities such as portland can run a degree or two warmer do to the urban heating effect. I just meant the climate as a whole wasnt directly effected.

  7. David B. says:

    Well, looks like I spoke too soon about the outflow winds not getting strong here. They’re picking up, and I’ve had several momentary power outages already. Hopefully this is the worst of it. Last month’s event made quite the mess here.

  8. steve says:

    Come on over to bend were expecting 6 in today

  9. Hal in Aims says:

    36 with fog forming here……..

  10. Jason Hougak says:

    A little more than 1″ of snow this morning up here in the foothills 1300′. Great start to the cold weather to come. Gonna be making snow tonight!

  11. David B. says:

    Still only 35 in Bellingham this morning, though dry and blustery. It’s an outflow event, but so far hardly “arctic”.

    • David B. says:

      Even Hope has yet to fall below freezing so far.

      Mildly breezy and 35 here. Looks like the strong outflow winds are missing me this time.

  12. schmit44 says:

    12/28/2014 Oregon (All) Temperature Summary

    High:55 at BROOKINGS( 79 ft) & Gold Beach (US 1(60 ft) & ILLINOIS VALLEY(1389 ft) & Yaquina Bridge W(120 ft) & Tillamook(63 ft)
    Low: 49 at EW1135 Yachats1(32 ft)

    High:19 at HOWARD Mt Howard(8150 ft)
    Low: 2 at CRANE PRAIRIE (5500 ft )

    Largest Diurnal Change: 29 degrees
    HEREFORD (34/5 ) (3599 ft )
    CRANE PRAIRIE (31/2) (5500 ft)

    Heaviest Rainfall:
    1.71″ at Mount Hood Meado(5249ft)

  13. Lurkyloo says:

    Wait for it …

  14. IceCold says:


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