Snow arrives as expected today, but morning commute should be okay for most of us

9pm Sunday…

It’s hard to believe, but Portland broke a snowfall record today with 0.1″ officially at the National Weather Service forecast office just east of the airport (122nd & Sandy area). Wait for it…the big total…

(kptv)

Yes, just 0.1″ officially fell and that is a record for the date. We’ve never had more than a trace on December 4th. That’s a testament to how little snow we get (most of the time) in our mild maritime climate. BTW, yesterday’s record is still just a Trace (in 1972), and tomorrow’s record is 1.5″ (also in 1972). That was at the beginning of a tremendous blast of arctic air that settled over the region for just under 2 weeks. I was only 3 and don’t remember, but I probably went sledding with older siblings on my parent’s orchard farm near Oak Grove in the Gorge. But I digress… Here’s a look at December snow the last few years, with some help from Santa

(kptv)

I think ALL of us from the metro area north and eastward at least OBSERVED snow in the air today, for quite a few hours. But temperatures were too warm for many of us OR the precipitation was too light for snow to really start sticking on the ground. We picked up less than .20″ worth of rain/snow today…very light stuff and models showing light precip were correct. Troutdale likely had far more than .02″, but wind-blown snow has trouble making it into the gauge.

(kptv)

A few more totals for you…lots of other 1/2″ totals didn’t make it into this graphic as well

(kptv)

In the end, I am pretty happy with the forecast; we expected a minor event, but some “sleddable” snow in spots and that happened. These marginal snow situations are such a pain to forecast. If it would have been 3-5 degrees colder, widespread snow would have stuck to roads throughout the metro area. Models sure nailed that quick evaporational cooling this morning. There were doubters as PDX sat at 40 degrees all night and was 41 at 8am. But as soon as precipitation fell into the very dry airmass, temperatures cooled quickly down close to freezing and have stayed there since. 41 at 8am down to 34 at 10am…impressive

(kptv)

Now the airmass is pretty much saturated, plus warmer air has moved in overhead so no more snow.

MONDAY MORNING COMMUTE

Temperatures are still hovering just a few degrees above freezing tonight, so the big question is “Will all these wet roads freeze?

The short answer is NO, for most of us. There will be some spots of freezing, but my gut feeling is we won’t be seeing widespread icing of roadways for the Monday morning commute in the I-5 corridor from Longview to Albany (our viewing area). There is plenty of cloud cover overhead and models imply we won’t see much clearing. The low level airmass is saturated. You’ve got to have clearing to have temperatures cool and roads freeze up. Plus there’s no fresh supply of cold/dry air coming out of the Gorge; pressure gradient is down to just 3-4 millibars across the Cascades. Last night at this time it was approaching 10! A lot less wind even out there.

One place that does stay frozen is the Gorge. Temperatures there are still all below freezing east of about the Corbett exit at freeway level. There have been numerous crashes out there in the past few hours. There is no warming westerly wind coming into the Gorge tomorrow, so you’ll only just rise a few degrees above freezing.

(kptv)

That’s it for now. Weather will be quite benign with very little rain through Wednesday, then a series of wet system arrives beginning Thursday and heading into the weekend.

22 Responses to Snow arrives as expected today, but morning commute should be okay for most of us

  1. tim says:

    Models are showing a big pattern flip for the US from cold in the west and warm in the east to warm in west and cold in the east the second half of December, the eastern states have yet to experience winter but that’s gonna change big time.

    • Joshua Lake Oswego says:

      The 18z operational GFS is an outlier. Certainly not looking warm anytime soon. Cooler than normal indefinitely. The east looks warm relative to average to me.

      • JohnD says:

        Don’t quite get Tim’s warm bias/passion. It’s just that for most of us on this blog it’s quite the opposite. Whatever I guess. Celebrate diversity.

  2. Ken in Wood Village says:

    The models have different outcomes from the 10th through the 13th right now. We should know more closer to Friday. It all depends on where the low pressure system goes. If it goes further North, we probably just see rain and maybe some South wind. If it goes South of Portland, we could see snow and East winds.

    The next couple of days we should have a better handle on what type of weather the Portland area will see 🤗❄️

    • Andrew says:

      Yeah looks pretty marginal again with a lot depending on how cold it gets in columbia basin and what tracks the systems take. If models are to be trusted this could be third time already this season that we’d see arctic air bump up against BC-Washington border and spill out into our region. On the one hand, it’s great because it at least gives us access to the cold with right system. On the flip side, we once again appear to potentially lose out on an arctic boundary that sets up a bit too far north for us to have a sustained and meaningful snow threat that isn’t so marginal. We’re so overdue at this point for a true north to south arctic outbreak. Still very early and models will undoubtedly change. Love the early season action! Plus the model riding and wishcasting is part of the fun.

  3. Gene says:

    Big difference between April snow and December snow: When we got 2-3 inches during that surprise snowfall last April, it was mostly melted by the end of the day. When we got the 2-3 inches of snow yesterday, much of it (especially in shaded areas) was still around today, and some will still be present tomorrow. Hopefully there will be more to come in the weeks ahead, when conditions are best for snow that sticks around for awhile

  4. Mountain Man says:

    One pretty interesting thing that can happen in a situation like yesterday with a deformation band, I picked up just shy of 2 inches yesterday at home in the Mt Rainier foothills at 1400 ft but to my west (had to run to Vancouver and back last night for family reasons) right at freeway level or about 200 to 300 ft el. there was at least as much snow, maybe more on everything except the pavement in the Lewis county stretch of I-5. No mountain lift in that situation. Just the collision of the wraparound moisture trying to move north and the overall flow moving south and that’s basically what a deformation band is. A really rare occurrence, perhaps once every year or two. If it had been 2 degrees colder, like instead of just above freezing, that would’ve been a major snowstorm for a good stretch of I-5 in sw Washington. Instead it was a slush storm.

  5. Roland Derksen says:

    Only 0.1 inches on the ground for Portland so far? Not much, indeed. Here we’re still seeing much of the snow we got a week ago on the ground surfaces. i don’t expect that snow to vanish for a few days yet.

    • JohnD says:

      Latitude no doubt does make a difference—Vancouver vs. Portland—even though both locations are in a basically marine climate—amid proximity to others, of course!
      No doubt like you, stats vary—sometimes widely—across the metro; hilly areas etc.
      The “official” NWS Portland snow recording
      site is in the Parkrose Neighborhood in the outer NE area of the city—near the Columbia River and east of the Portland Airport.
      Interestingly all weather stats except snow I believe are recorded at the actual airport.
      Sure hoping that the models gather momentum for a continued great winter!
      Like a lot of us, I’m always pulling for it!

      • Roland Derksen says:

        Yes, John you are right- and I can sure talk about differences that occurr across my city. In any event- it looks like temperatures are warming in the next few days.

  6. WEATHERDAN says:

    36 and foggy now. If it stays foggy we may not even get out of the thirties today. Amazing how consistently cool it has been this Autumn and Winter so far. Not super cold but below average almost every day since early November. No AR or Arctic blast in sight but maybe some wind. We shall see. Peace.

  7. Ken in Wood Village says:

    Hmm, the 12Z Euro run was a little interesting starting Sunday 🤔❄️

    • Andrew says:

      Always nice to see EURO show signs of life but yet to be supported by ensembles. GFS had also shown the potential for a nice blocking ridge to reestablish next week giving us another shot at colder air. Incidentally, the EURO runs put the ridge right over the top of us. Bottom line is that after a more zonal flow this week with some potentially decent storms starting thursday and going through weekend, there is very little model consistency and confidence. Hopefully things start to align over next few days so we at least get a sense for where things are trending.

      • Ken in Wood Village says:

        I agree Andrew. Just looking at the 18Z GFS, it’s showing a sign like the 12Z Euro around the same time frame (the 12th and 13th). It’s time to watch how the models play out the next couple of days.

        • Doinko - Bethany says:

          Surprised that the Euro is colder/snowier for that system around the 12th/13th. If it verifies that would be an amazing Willamette Valley snowstorm. 6-12″ of snow followed by cold weather. Obviously that’s far out but maybe it’ll happen!

  8. OC550 says:

    Well, the answer to the question was YES…roads will freeze in the morning. Saw at least 3 wrecks on 205 and neighboring roadways. Definitely icy and slick out there with the clear skies. Be careful!

    • West Linn 200 says:

      Yeah not only is there no cloud cover, but it’s below freezing here right now at 31F. Schools have a 2-hour late start for it.

  9. Ken in Wood Village says:

    I’m keeping an eye on the models because they are showing a possibility of a windstorm coming up over the weekend. The GFS is showing two windstorms. One on the 10th and then the 12th. The Euro showed one on the 12th. So we need to watch the models closely.

  10. ViRGE says:

    On behalf of all of us in Salem that didn’t get any snow, you guys suck! =P

    Meanwhile, looking at the weather forecast and Mark’s comment of “warmer air has moved in overhead”, am I right in thinking we’re moving back in to a thermal inversion situation? The air quality away from the gorge is already going to pot again.

  11. Paul D says:

    Hi!

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