Another Tough Snow Forecast; Tuesday Night & Wednesday

3pm Monday…

The last of the cold temps from the east wind are (temporarily) gone in the metro area and we’ve moved into the pattern I mentioned last night…low level rain showers and snow showers in the hills.  At times the snow has been sticking down close to sea level in the heaviest showers, but the showers will be tapering off this evening.  So everything looks clear for the evening commute.

There is one minor challenge and then one big one headache forecasting the next 48 hours.

First…the easier one:

A weak system snuggles right up against the north Oregon and south Washington coastline tonight.  There is a surface low pressure system that’ll move onshore right around Astoria late.  Take a look at our RPM model for

rpm_cloud_snow

That causes wind to go calm or light easterly (we lose the mild onshore flow) anywhere north of Portland.  Combine that with the leftover cool airmass overhead and it’s possible we see sticking snow well below the 2,000′ models suggest.  As a result:

  1. Later tonight snow may stick down close to sea level north and west of a Hillsboro to Vancouver line.  That means there could be a dusting or even a bit more from St. Helens to Kalama to Kelso.  Maybe Battle Ground too.  Not a big snow-producer, but it’s a tough call.
  2. Most likely any sticking snow will be confined to the top of the West Hills or higher in the metro area.  East of Multnomah Falls in the Gorge it should fall as snow too due to a light easterly flow continuing over there.

Beyond that not much happens tomorrow during the daylight hours, then the big forecast challenge arrives.

Another big storm will be moving right across the middle of Oregon, taking a path very similar to our last snow event in mid-December.  That was the one with the Traffi-Pocalypse on the 14th.  Remember that afternoon?  The central/southern part of the state is going to get hammered once again with a big snowstorm.  That includes Bend, Burns, Madras, Lakeview, Klamath Falls.

The big issue, just as in the previous storm, is HOW FAR NORTH DOES THE PRECIPITATION GO?  Just about all models cut off the precip somewhere around a Tillamook to Clark County line, with rain to snow developing south of that line and mainly dry to the north.

TUESDAY/WEDNESDAY HIGHLIGHTS

  • Most of the daylight hours Tuesday will be dry
  • In the afternoon the strong & cold east wind will be spreading out of the Gorge again and into the metro area.  Gusts likely exceed 40 mph by evening east metro again…brrr!
  • By sunset (5pm), rain will have begun in Salem and Eugene, spreading north
  • At some point after 6 pm rain should arrive in the metro area, with temperatures a bit above freezing.  At this point the evening commute appears to be fine in the metro area
  • Within a few hours temperatures will go below freezing and rain changes to snow
  • Snow falls through the night tomorrow night and ends Wednesday AM.  Accompanied by strong east wind east metro, expect blowing and drifting late into the night.
  • 1-4″ is possible in the metro area, likely most south, lighter north <<< THIS FORECAST WILL LIKELY CHANGE THE NEXT 18 HOURS
  • If this occurs, Wednesday will be a snow day for the kids and lots of workers too.
  • Wednesday the flurries end and we go cold/sunny the 2nd half of the week; just like after last week’s snow.  Snow/ice will gradually work/melt off the roads.

We’re still 30 hours away and have 2 more model runs to firm up that snow total a bit.  A couple of models keep us totally dry with all the action staying south.  I think that’s unlikely, thus the 1-4” snow forecast.  More info this evening and a final look mid-morning tomorrow should give us a much better idea of exactly what to expect.

COMMUTERS/SCHOOL ADMINISTRATORS

Even though the Tuesday evening commute looks fine in Portland/Vancouver/Salem, pay very close attention to the forecast in case for some reason the arrival of precip and cooling (rain to snow) speeds up.  Imagine if everything speeds up 5 hours and we get rain by 2pm and freezing at 5pm.  That would be bad…so pay attention.  Schools should be just fine tomorrow too since no modeling/forecast shows anything interesting in the 2-4pm timeframe.




This situation is very similar to the December 14th storm…a big precip producer moving across mainly the southern portion of the state with the NW tip of Oregon (and metro area) at the northern edge of the precip band.  A few things stick out on the maps/models.  First, several models bring a 2nd weak low or at least surge of moisture farther north right over us late tomorrow evening and during the night.  The ECMWF is most insistent on this and it’s thinking 2-5″ of snow, the GEM is similar and very white too.  Both these models give a real snowstorm for most of the metro area.

ecm_snow

On the flip side the NAM is keeping just about all precip to our south.  Well, it IS the NAM…moving on.  I’m pretty confident that we’ll see at least SOME snow, but luckily as mentioned above we do have a couple more model runs to fine tune the forecast.  It also helps that just about all the event is happening when most people are home…after the evening commute and before the morning drive.  I’m so glad that this isn’t predicted to begin at noon and cool down to freezing around 5pm.  It’s starting later and we’ll have a relatively “warm” airmass as the event begins.  Of course there is the outside chance that we somehow get freezing rain to start, but I think that’s unlikely because the upper-level airmass will cool first before the lowest levels freeze up.

One BIG thing to remember from that December 14th storm.  Remember the precip was supposed to move no farther north than Tillamook to Clark County?  Instead snow fell all the way to Astoria and Longview!  A change of 50 miles will make a huge difference tomorrow night!

kitty_windowlicker

Keep those kitties watching out the window…yes, we’ve found our first window-licker-wishcasting cat.  Sign me up!  Thanks to Sara for the pic.

More later…Chief Meteorologist Mark Nelsen

63 Responses to Another Tough Snow Forecast; Tuesday Night & Wednesday

  1. Destiny says:

    Does this mean Albany will be getting more snow than the metro area??

  2. Marc (Brush Prairie, WA) says:

    As long as Battle Ground Lake gets 0″ of snow this week, I’ll be happy.

  3. Kitty wehage says:

    How much are we going to get in Longview?

  4. Diana F says:

    NWS has now backed off of Valley floor/PDX snow fall for tonight due to temps…or some such nonsense 🙃

    http://forecast.weather.gov/product.php?site=PQR&issuedby=PQR&product=AFD&format=CI&version=1&glossary=1

  5. Jake-(Gresham) says:

    Bit the bullet and went with this puppy; if not a late birthday present for myself: 😀

    https://www.amazon.com/Ambient-Weather-WS-1400-IP-Monitoring-Radiation/dp/B00O9YIEJW/ref=cm_cr_arp_d_product_top?ie=UTF8

    Now if only I had Prime to get it here before this next Winter event. Dang it.

    • Diana F says:

      lol!! Me too! And I have PRIME (side eye with tongue sticking out)

    • Jake-(Gresham) says:

      LoL! Yea… same exact sentiment here.

      Glad you came to a conclusion. I thought it no brainier out of all the models after comparing for myself.

      Only CON I’ve read is that sometimes the wind cups get stuck when it snows. The solution found was to spray some silicon to make the snow slide away and not clog them up / get in the way.

      Just FYI!

  6. marinersfan85 says:

    Just curious… What’s the interview process at the NWS?

    Pulse check then put a mirror under their nose?

  7. Leeateea says:

    So does Salem totals look similar to Portand or is it looking a touch more?

    • Jake-(Gresham) says:

      Not to be the Debbie downer but Salem looks to be in the area of warm to cold air interaction for a good portion of the weather system’s movement over the valley.

      So, sleet and ice pellets. ;(

  8. Sapo says:

    00z runs have been impressive tonight…have not backed off, actually gotten more snowy if anything. Oh and the NAM showed up to the party.

    00z GFS 2-6″, (4-6 totals westside and 2-4 east side)
    00z NAM 2-4″ (again higher totals westside)
    00z GEM 3-6″
    00z WRF appears to be 2-4″ by the time it’s done but could be less

    Euro is later on tonight

    • Mark says:

      Will Mark turn out a “band” chart of snow totals, or keep it generic – less north and east, more west and south?…

    • Joshua Downtown PDX says:

      The 18z and 00z RPM really backed off on the snow. Essentially down to zero now for Portland. Model riding is fun, huh?

    • Jake-(Gresham) says:

      Meh, one model having two runs doesn’t constitute concern.

      What it does tell us is that consolidation is not solid and thus any outlier be smoking something a bit too fine cough cough NAM.

  9. Jake-(Gresham) says:

    To put this in more layman’s terms. As the low weather pressure system comes ashore somewhere parallel to Eugene (that circle is basically the low pressure disturbance) a ridge of high pressure sits ideally in British Columbia just North of the border with Washington (the other circular level disturbance):

    http://www.pivotalweather.com/model.php?m=gfs&p=prateptype_cat&rh=2017011000&fh=33&r=conus&dpdt=

    Now hit ‘play’ and watch as the low pressure system comes ashore. Rides the jetstream a little North, stalls over the Cascades, and dumps all over the Willamette valley (slide 08 to about 12):

    http://meteocentre.com/models/get_anim.php?mod=nam&run=00&stn=PNMPR&mode=latest&map=na&lang=en

    Freaken insane.

  10. Near Durham elementary 167' says:

    Looks like NAM just got on board…

  11. Anonymous says:

    Since the Portland forecast is dependent on the extent of the system and not temps, is it fair to say the south valley (Corvallis/Eugene) should expect some accumulation Wednesday AM?

  12. Camas500 says:

    Why is there a Winter Weather Advisory instead of a Winter Storm Watch? Snow path too uncertain, or not enough snow for a Watch/Warning regardless of who gets the most?

    We got an unexpected 2-3 inches of snow here in Camas at 500 ft this morning. Ironically our biggest snow so far this winter was never forecasted in advance. Seems like those turn out to be the biggest ones around here.

    • Jake-(Gresham) says:

      This just evolved. Obviously as weather enthusiasts we’re going to talk about it first before there’s a chance for an official report being put out. It’s the Government (i.e. NOAA).

      What’d ya expect? Nachos and wine too? 😛

    • Diana F says:

      I was just thinking about this, Camas500–I am pretty sure that anytime we have gotten a nice little surprise bundle of snow, it was not forecast by anyone, and that’s happened a lot over the years. That’s why half the time when snow IS forecast, I know in the back of my mind, WAY back there, it means “snow is now canceled”. So now that I’ve seen the NWS say 1-3 inches? We can fuggetaboutit!

  13. Andrew says:

    Some of the local forecasters seem pretty darn confident that precip stays south of us, yet some of you are saying we’re in line for moderate accumulation and potentially something bigger. I assume the next couple model runs will be telling. Anyone have a good link for precip predictions as we get closer to tomorrow evening? Thanks.

  14. JERAT416 says:

    Between December 2008 and a handful of other years, I know I’ve seen a lot more snow and ice in past winters. However, it has been a few years since I’ve seen this many ice/snow, close call events in a long term pattern. I am tired of the ice storms though.

  15. JohnD says:

    I recall that in the great winter event of Dec. 2008, most of the storm energy and snow totals stayed north–e.g. Portland area, much less south. This year quite the opposite so far. This will be our FIFTH bonafide window of major opportunity. Hopefully this is the one!

  16. JJ78259 says:

    I have a hunch that it will start snowing tomorrow morning in Portland and won’t stop till some time Wednesday for 8-10 inches just a hunch

  17. Deer Is. at 750' says:

    Left for work at 5:30 with a slow melt going on. Rain going down the hill and almost snow like in Scappoose. Made it to NE Columbia and 60th and saw melting all day. Got home to nearly 4″ of new snow on the ground. I had better traction in the driveway with the new new snow than I had this morning with wet ice. Truck temp said 34, alarm clock says 32. Can’t wait to see what I wake up to tomorrow.

  18. Paul D says:

    Another event to help Mark earn his pay 🙂

  19. Jason Hougak says:

    2″ of unexpected snow here in the foothills today.

  20. PDXGSXR says:

    Thanks Mark – you are the winter storm forecast in Porltand as far as I’m concerned.

  21. Tyler Mode in Battle Ground says:

    21 years of record and the low of 13.4 at my station in Vancouver was my lowest January temp ever. Previous was 13.8 degrees in 1996.

  22. Portlandsk8er says:

    Well said, as always. Keep it coming…the more detailed, the better.

  23. JF says:

    Another thoughtful and thorough summary! Thanks for doing the extra work!

  24. JJ78259 says:

    My cats will be enjoying the 81 degree Temperature in San Antonio on Wednesday they did really like the few snow days thay had in Milwaukie. They had a hard time wanting to go outside if you know what mean. The cats for some reason like sleeping on the furniture around pool when it’s 80 degrees.

  25. cgavic says:

    update……interesting..after our snow event, I had to run some errands around sandy. talked with some employees at one spot. they indicated it was snowing hard in “downtown” sandy for same amount of time as where we live, but they received no accumulation. when I made my round, I head east through sandy, then drove down into the little valley we live in…….37 degs. but 1 to 2 inches in our little valley.

  26. Jake-(Gresham) says:

    Thanks for the update Mark. You’re solid man on keeping the public up to date. Much appreciated.

  27. cgavic says:

    Corbett will always get more snow and colder temps than those of same elevation just south of the columbia river gorge.

    at 885 ft. in sandy, this morning, for two hours had heavy snow shower with huge flakes…..ended up with 2 in. snow. temps. 36 degs.

  28. Joshua Downtown PDX says:

    Thanks for the preliminary forecast, Mark. I hope you are getting a bonus or something soon. This winter has kept you very busy. Always good to keep your tools sharp. In your case, that would be your brain.

  29. Alan PDX says:

    I’ve never commented before, but have enjoyed this blog for many years. Mark – Your forecasts always are on point. I hope the ice will stay away. I fell this morning after slipping on the ice and broke my ankle. From now on, I de-ice the steps every time!

  30. Thanks for the update, Mark. We’ll keep up the watching and waiting until tomorrow!

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