Cold Air Moving In

Real calm weatherwise this evening…the calm after the “storm” I suppose.

Cold and dry now as the last flurries seem to be just about gone on radar and east wind is picking up across the Metro area.  Our dewpoint just dropped about 5 degrees in the last hour at the station.  We’re freezing up nicely across the region as the modified arctic airmass moves in.  The low dewpoints will help dry out roads, so I don’t expect a major huge mess for the morning commute; just areas of ice and some leftover snow on the hills or shady spots. 

I’m really looking forward to the sunshine the next two days.  Though it’ll be chilly (and breezy tomorrow), it’ll be nice to be blinded by the bright late February sun.  Speaking of calming wind, perfect radiational cooling should drop us to right around 20 tomorrow night.  No snow cover to help for most of us after another sunny day in the 30s, but it’ll still be unusually cold for this late in the season.

I’m keeping an eye on the transition into wet weather…appears to be Saturday evening or night as precipitation arrives.  Good chance of a snow start with real nice evaporational cooling, but southwest wind picking up during the night means it can’t last that long.  There is not dry/cold air coming in from the east at that point.  In those situations it’s usually not a significant snow event.  I also notice the precipiation amounts are quite light for the first 12 hours; that doesn’t help if you want snow either.  The main message is that it doesn’t look real exciting right now, we should wake up to rain on Sunday morning.  At best rain with some leftover snow melting on the ground.

I’m also keeping a close eye on a deep low forecast to move north up the coastline late next Tuesday.  The last two runs of the GFS have been impressive, especially the latest at 00z.

In general, as March begins, we’re heading into classic La Nina early spring conditions; cool and wet.

Here are the snow total maps from today…click for a better view.  Notice how Clark County had more than the top of the West Hills!

Stay warm!

Chief Meteorologist Mark Nelsen

297 Responses to Cold Air Moving In

  1. pappoose in scappoose says:

    New post

  2. EA_TTD says:

    Hey Mark, how about a non-binding 18z GFS analysis? Are my eyes deceiving me for Monday morning and Tuesday??

  3. cherie in vernonia says:

    totally gray here…was just gonna jump in & ask if there was a change in the forecast. NWS says 9 degrees for me tonite 😦

  4. Gidrons says:

    Latest from NWS on weekend snow:

    WHILE CONVENTIONAL WISDOM FOR THE REGION SUGGESTS A
    QUICK CHANGEOVER TO RAIN AT LOW ELEVATIONS WITH SOUTHERLY NEAR
    SURFACE LEVEL WINDS…MODEL THERMAL PROFILES INDICATE THAT
    PRECIPITATION INLAND IS LIKELY TO REMAIN MAINLY SNOW SAT NIGHT INTO
    EARLY SUN MORNING. GIVEN THE PERSISTENCE AND CONSISTENCY OF THIS
    IDEA WITH THE MODELS…BELIEVE THIS IS A CASE TO GO AGAINST THE
    CONVENTIONAL RULES OF THUMB…AND KEEP A THREAT OF LOW ELEVATION
    SNOW INLAND VALLEYS UNTIL SUN MORNING.

    • Ben (Beaverton - 775 ft.) says:

      I was wondering when they would trend this way. This winter has thrown us curveball after curveball, why not another one?

    • Josh "The Snowman" From Everett, WA says:

      If 00z holds on to the cold air longer like the 12z and 18z then we will see a forecast change for sure.

      -20 850 temps 100 miles north of the WA/Canadian border and they are forecasting 48 degrees on Saturday.

      No friggin way.

  5. PaulBeaverton says:

    Every winter I learn so many new things regarding the weather… this year:
    1. Thicknesses – Thanks Mark!
    2. Model Reading (and riding) – Thanks EVERYONE!
    3. Evaporational cooling
    4. Gradients – Thanks Rob!!

  6. PaulB/Eugene says:

    Latest GFS guidance has low tonight of 11 for EUG, SLE, 9 for HIO, 10 for Vancouver, 15 for PDX. With offshore flow, clear skies, significant areas of snowcover inland (other than Columbia Basin) where the air comes from…should bottom out tonight with lows having a good chance of getting within a degree or two of these. PDX getting to 15 of course depends on winds calming down for at least a few hours tonight.

  7. Jory (Sandy & Downtown Portland) says:

    Will these incoming clouds cap tonight’s cooling?

  8. Wendy-Silverlake,WA says:

    Any word on if the stuff on the radar up here is making it to the ground?

  9. stevied (North Portland) says:

    Hmmmmmm… continued.
    About the 18z…

    That low early Wednesday morning next week wants to (at this point) hit the Central Oregon Coast and pass JUST east of PDX. With offshore winds, and just the right location, COULD be interesing here. Winter has not let go yet. Not sure it would be quite cold enough, but heavy moisture involved, -3c, and offshore or wrap-around flow.

    HR 114:

    HR 120:

  10. timmy - scappoose says:

    18z hr 114-120? what do you see Rob? anyone?

    • W7ENK says:

      I SEE A MONKEY!!!

      No, actually, I see a 998Mb low off the Southern Oregon coast, and the 0C line extending right up the Willamette Valley directly over Medford -> Portland. Then the Low moves just to the South of Portland up to around Karl’s house as it weakens slightly to 999Mb. Looks like an awful lot of chilly rain, too!

      Am I seeing this right?!?

    • W7ENK says:

      These are the ones I looked at, why are they different from Rob’s?

      18z GFS 114:

      18z GFS 120:

    • W7ENK says:

      Sorry, stevied not Rob… my bad.

  11. With the east winds expected to diminish along with some areas here that are still snow-covered coupled with Td readings about half of the actual temp reading, should be a real cold night here in Orchards…

    Looks like my high today is 35.7°.

  12. stevied (North Portland) says:

    Hmmmmmmm….

  13. O.C.Paul says:

    30.9 in Oregon City. May ‘just’ make it above freezing to set up for a bone chilling night.
    Man, I love real winter.

  14. Andrew Johnson says:

    Here in Silverton it was 37.1 at 2pm now 36.9. It couldn’t be starting to recede from the daytime high already could it?! 🙂

  15. EA_TTD says:

    18z GFS is, in a word, interesting….

    • timmy - scappoose says:

      hr 54 doesnt make sense, has to be a glitch. that low wouldnt make landfall and pop offshore again in 6 hours

    • Gidrons says:

      its a lot more interesting than the Euro

    • Rob "Wrath" S.E. Portland says:

      Yeah very.. I like how the strong arctic front is right on the BC/WA border and also is there a trend with the low Tuesday to dig further and further south? …. Also if the low Saturday/Sunday is weak it may not induce as much warmth as expected. It may serve to kill off the cold high pressure over eastern Washington, but this looks intriguing.

    • W7ENK says:

      Yeah, but Rob, that would mean something would actually have to work out in our favor with regard to COLD over WARM, and that just doesn’t seem too likely with the way things have been going this winter.

      I think the only reason why this current cold snap wasn’t completely erased from our area mere hours after it moved in is because the warm to our South and West forgot to set itself up in a favorable position to completely screw us over. Still, some areas got screwed over anyway, but that’s beside the point… this time. 😉

    • EA_TTD says:

      This pattern is going nowhere soon according to the GFS. 850T’s below 0 the whole time through hour 180.

  16. Andrew Johnson says:

    33 at 2pm at PDX. Unbelievable under sunny skies at the end of February! I’d wager a guess that if this was late December/early January it’d only be in the mid-20s! Down the valley it is pretty chilly as well 36 at SLE, 35 at EUG. I also think that the 37 at Newport is pretty amazing as well!

    • Rob "Wrath" S.E. Portland says:

      Yup. Now just imagine a widespread 4″ snow cover throughout western Oregon. Very impressive…

    • Andrew Johnson says:

      Yeah now if we can just start getting widespread snowcover with these arctic blasts. If December 2009, November 2010, and now this one had had a widespread 4+ at onset…Wow! Over on Western they are saying that in the 2006-2011 time span we’ve now had 7 arctic outbreaks starting with the one in February 2006. Of course they are counting Nov. 06′ in there too which I don’t really think counts since it never really made it down here. Either way its the most in that span since 77-82.

    • Emily Waldman says:

      @Mark & Rob: we had a beautiful sunny day up in Longview. Now the clouds are rolling in is there more SNOW to be had this evening up here? We will be an icy mess Sat. morning not looking forward to the normal 10 minute drive down the hill over bridge to Kelso! Now 20 min. & chains.

  17. Boydo3 500' North Albany says:

    No doubt some nice snow on the mountain. But the wind chill at Hoodoo is around -22. Frostbite could be a real danger.
    http://www.callatg.com/~nsps/weather.htm

  18. timmy - scappoose says:

    I bet we will get some quick snow tomorrow night, but i bet it will last longer than most expect. The low isn’t incredibly “low” the flow looks like it is onshore, but with the wetbulb, timing, and nature of the low as well as distance from us, we may score a bit before it switches to rain.

    • W7ENK says:

      So, basically a repeat of 12/29/2009?
      That would be nice.

    • Rob "Wrath" S.E. Portland says:

      My concern would be increasing SW winds aloft and precip either not being heavy enough or steady enough to take advantage of any possible evaporative cooling that may be available.

    • Josh "The Snowman" From Everett, WA says:

      Yep, Rob. WNW flow in the upper atmosphere is going to be a killer for heavy QPF in pdx and the willamette valley.

      Should be good flow for me, but I am always worried about the Olympics shadowing me as well. According to the NWS, it is looking like a Seattle south rain shadow so we will see!

    • timmy - scappoose says:

      i am not good at forecasting wind speeds, but the low placement and depth wasn’t convincing against what i saw.

  19. Cgavic sandy Oregon 1,100 ft says:

    East winds at 15 mph
    25
    3.5 in.

  20. W7ENK says:

    NWS PORTLAND – MULTNOMAH, CLACKAMAS AND MARION COUNTIES
    …AVALANCHE WATCH FOR HIGH TO EXTREME DANGER SUNDAY…

    http://inws.wrh.noaa.gov/weather/alertinfo/1603519

    Watch out for avalanches, people… keep your eyes open!

  21. Wendy-Silverlake,WA says:

    We just spent the last two hours sledding down the driveway. Straight up and down with winding corners and the section we were doing is about 1/4 mile long. That was so much fun. Where the sun made it through the trees thouh is down to bare gravel, sucky, it ended most of the fun. I can’t believe how warm it has gotten.

  22. Garron near washington square says:

    Please forgive me if I slaughter his name, but, Nick Allerd on KGW called for an icy mess on Monday night? I caught the end of his forecast. Did anyone else see something for Monday evening?

    • Mark Nelsen says:

      I think they like to hype forecasts/weather more than any other tv station in town.

    • W7ENK says:

      Hahaha! I’m glad to know I’m not the only one that thinks this… 😆

    • W7ENK says:

      Hahaha! Mark, I’m glad to know I’m not the only one that thinks this… 😆 I had to seriously bite my tongue when you told me that the official snowfall for downtown is measured at their studio… how convenient! 😉

    • Garron near washington square says:

      Thanks Mark, I really liked Jim Little when he was there, but I think weather news has gone to dramatic forecasting in order to draw away from your charismatic following.

  23. PaulB/Eugene says:

    Coldest for so late in the season records to fall tonight:

    Need to get below these temps for the following cities:

    McMinnville: 16/1962 (since 1894)
    Oregon City: 14/1962 (since 1911)
    Hillsboro: 17/1962 (since 1929)
    Eugene: 18/1962 (since 1892)
    Corvallis: 12/1971 (since 1889)
    Roseburg: 16/1962 (since 1899)
    PDX: 19/1955 (since 1941) (note was 10 in 1890)
    Salem: 10/1962 (since 1892)
    Medford: 10/1962 (since 1928)
    Longview: 17/1962 (since 1925)
    Olympia: 5/2011 (since 1948)
    Seattle (SeaTac): 18/1962
    Astoria 19/1962

    If forecasted lows verify, all except Salem, Seattle, Olympia will be broken.

    • PaulB/Eugene says:

      and Corvallis…although you never know.

      There is virtually a 100% correlation between temperatures this cold this late in the season and extreme windstorms about 8 months later if you haven’t noticed…so let’s issue the High Wind Warnings for next October/November already…when does the CFS get out to October? 😉

    • W7ENK says:

      I know EXACTLY how to make that windstorm correlation NOT verify next fall… I’ll go make an announcement on Facebook and Twitter right now. That should about do ‘er in, don’chya think?! 😆

      Yeah, because every time I say something to my friends on social media about upcoming weather craziness, no matter how “locked” in it looks, it always fails and I end up making an @$$ of myself. 😦

      Fool me once, shame on you.
      Fool me twice, shame on me…
      Fool me a third time, in one winter? FML.

  24. garron near washington square says:

    The record low at PDX was safe last night, got down to 25 needed to get to 21. HIO “I think” tied their record of 23 degrees last night. The low temps may fall tonight “if” the wind dies down a lil. PDX’s low of 19, may be in jeopardy. The record low/high temp for today should get shattered. It’s only 32 now, the record for a low/high today is 40.

    • Andrew Johnson says:

      Yeah that will fall. I bet PDX only ends up in the 34-37 range. SLE should end up in the 36-40 range. Silverton is at 36 now and will probably end up around 40, or course it will probably be one of the coldest tonight. It seems like in these situations it may run a degree or two warmer than most places during the day, but drops off like crazy at night. Though it did run a couple degrees colder than SLE for daytime highs in early January.

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