No Snow Saturday, but Ice/Snow Storm Gorge For Monday

10:30pm Friday…

First, don’t get too excited about snow anywhere close to the metro area tomorrow.  Sticking snow level drops to around 1,500′ in the morning and stays there all day.  We’ll just see scattered showers the first half of the day so it’s possible anyone could see a snowflake mixed in with the showers but that’s it.  Those of you above 1,000′ in the Cascade foothills have a better chance of a dusting early in the day since it’ll be wetter up against the mountains.  Same thing in the Coast Range. More obvious will be the change from highs in the upper 50s to afternoon temps just above 40…that winter feeling in the air is back!

Tomorrow night and Sunday we have some modified arctic air working down out of Canada and into the Pacific Northwest.  It’s not as cold as the last event two weeks ago and sure isn’t an “arctic blast” with 850mb temps only around -7/-8 and high temps in sunshine around 40 Sunday.  But quite a chill again and this time it’s straight from the north instead of coming at us from the northeast.  That said, the effect is the same.  Easterly gradient through the Gorge builds quickly and by Sunday morning it’s in the 8-10 millibar range from The Dalles to Portland.  Sunday will be a sunny, but very cold and windy day across the entire metro area.  Windchill temps will likely only be in the 20s and lower 30s all day!

Things get REALLY INTERESTING late Sunday night and Monday…Moisture moves north from the upper-level low off the California coast and forms a sort of deformation band directly over northern Oregon and the extreme southern part of Washington.  This sits overhead for more than 24 hours.  You can see the convergence of the northern part of the jet and the flow from the south midday Monday… wrf_36kmMon

 

As of this evening, all models are on board with this general idea, which brings up three questions:

1. How cold will the airmass be?  Cold enough for anything in the Gorge to be frozen through all of Monday.  PROBABLY not cold enough in the metro area for frozen, although the timing of precip arrival (at sunrise or soon after) would increase the chance for something frozen.

2. How much moisture?  This is a tough one because the placement of the precipitation is farther north on some than others.  Some models are far wetter than others too.  The ECMWF is a real soaker, but keeps the heaviest stuff just south of us, like what happened a couple of weeks ago.  It shows 1/2″ liquid over PDX, but 2″ around Albany by early Tuesday!  The GFS is a little wetter and farther north showing around 1″ over PDX.

3. What precipitation type?  This is the easier one!  Hopefully all the forecasters can agree this time that whatever falls west of the Gorge will be in liquid form.  The atmosphere 2-4,000′ up is forecast to be even warmer than two weeks ago with forecast soundings showing temperatures as high as 40 degrees 2,000′ or so overhead.  It’ll be either rain or freezing rain Monday morning in our area.  In the Gorge, freezing rain at the west end and a wintry mix central/east end.  Could start as snow and then change to freezing rain.

If heavier precipitation forecasts pan out…the potential exists for a very disruptive snow/ice storm in the Gorge again…That’ll be twice so far this season by December 1st!

I work Saturday and Sunday…actually every day through next Friday…so I’ll update again as we get closer.

Chief Meteorologist Mark Nelsen

 

122 Responses to No Snow Saturday, but Ice/Snow Storm Gorge For Monday

  1. David B. says:

    Dead calm now. Atmosphere is decoupling nicely. 23 degrees. Upper teens by morning? Time will tell. The madrone trees on the island will not be happy if that happens.

  2. JERAT416 says:

    All these people seeing snow, and I saw jack squat. Wind, rain, clouds, sun, hail, etc but no snow. What a time to be up on the mountain! However I’m so glad I am not on any hills right now with black ice!

  3. Jeff NE Portland says:

    I’m still thinking something will happen into Monday morning. Just a thought. What do you think rob? Its been a while since your last update.

  4. Still wondering about freezing rain Monday…

    • Tyler Mode says:

      Looks less and less likely. Recent models have trended back south with the moisture.

    • Sapo says:

      NWS is still saying there’s a good chance of freezing rain Monday…we’ll see what tomorrow’s runs have in store for us. Mainly the important factors will be the location and timing of the precipitation. We’ll probably need the precipitation arrival here about 6-8 AM or so on Monday for any really decent chances of widespread freezing rain. We’ll see tomorrow how cold we are going to get on Sunday night, and what models do with the precipitation Monday morning. Right now models aren’t looking too great for widespread freezing rain on Monday morning, though. WRF-GFS has light precipitation arriving about 10 AM Monday in the southern Metro area, but most parts of Portland not even seeing rain. MM5-NAM keeps the precipitation SUPER far south, not even close to getting near Portland. Again, we’ll see what tomorrow’s models show, but right now, the trend is in the wrong direction if you are wanting freezing rain.

  5. David B. says:

    Really quieted down here in the past hour or so. Presently 25 degrees. Low 20s definitely look like a lock for tonight. Maybe colder.

    • David B. says:

      Don’t worry, it will get there. It often takes an extra day (after the Fraser outflow commences) for the Columbia Gorge outflow to kick in.

  6. alohabb says:

    With the heavy downpours we had in Aloha an hour or so ago, and temps now to 33…guess we should be ready for icy roads tonight!

  7. Jake-(Gresham) says:

    Hey guys we got some snow mixed with rain here about 2 hours ago. I think this air mass is a bit colder then anticipated?

    • Sapo says:

      I don’t think the air mass is that much colder than models forecasted…In fact all over the Portland Metro area people have been reporting a rain/snow mix, and there definitely was a good possibility of a rain/snow mix today. So I don’t think that snow mixing into the rain is an indicator that the air mass is colder than forecasted, but someone else may know otherwise.

  8. vernonia1 says:

    hope someone can send me the link I want…see post above

  9. Sapo says:

    Can anyone give me a quick overview of what the majority of the models are saying for ice in Portland on Monday? Which models have a good setup for an ice storm here, which ones don’t?

  10. Wendy-Silverlake, Wa says:

    There’s going to be some icy roads tonight/tomorrow morning. It’s currently 30 here and where the snow melted it is solid ice.

  11. David B. says:

    Lost power about 9:20 this morning. Decided to run errands when it got too cold. Was back on by 2:20 when I returned. Temperature has “warmed” up to 29 now, from a low of 27 earlier today. That’s probably the daytime maximum, as the sun is already getting low and indirect.

    Outflow winds continue to rage, though they have weakened a bit since this morning.

    All an all, a significantly more dramatic day than I had been expecting, thanks to the winds. Easily the strongest ones I’ve had so far this season. NWS really should have at least issued a wind advisory for areas near the Sound. Away from the Sound, outflow winds seem much less strong, so it’s a pretty localized phenomenon.

  12. Longview 400 ft says:

    Currently 32.5

  13. vernonia1 says:

    Bellingham 1:53 pm PST 26
    Everett 1:53 pm PST 26
    Ft Lewis 1:58 pm PST 32
    Chehalis 1:09 pm PST 35
    Castle Rock 2:09 pm PST 36
    Kelso 1:55 pm PST 36
    Airports
    PDX 1:53 pm PST 40
    Hillsboro 1:53 pm PST 41
    Troutdale 1:53 pm PST 39
    Scappoose 1:53 pm PST 37

  14. Boydo3 N. Albany elev. just under 500' says:

    Monday looks dry for PDX according to this morning’s MM5
    http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_e_or_pcp1+//72/1

  15. Snow Maniac says:

    pouring snow on bull mountain!! elevation 350 feet

  16. Temp dropping quick mpisure moving in tiny snow flakes

  17. Goducks09 says:

    Looks like the modified arctic boundary should move into the metro area in the next 90 minutes or so… Wish there was a bit more moisture associated with it!

  18. The shower hopping over Portland is pretty much the last chance for snow.😞

    • Snow Maniac says:

      looks like we have one more good band coming. just west of North Plains right now. hopefully we get something out of that

  19. Dave in SW PDX (235') says:

    Rain/snow mix here, temp 39°F.

  20. Goducks09 says:

    Little “snow shower that could” here on the waterfront in SW Portland.

  21. Katrina in forest height says:

    All snow coming down at the moment, but it’s 37 degrees. 800 ft near Cornell rd and skyline.

  22. alohabb says:

    Heavy snow shower in Aloha..obviously because of heavy rain band…but fun to see!

  23. Ryan in Camas says:

    It’s snowing in Camas / Prune Hill!

  24. Modified boundary just moving into Kelso. Temps falling and NE wind increasing.
    http://www.wrh.noaa.gov/mesowest/getobext.php?sid=KKLS&table=1&banner=off

  25. vernonia1 says:

    mostly rain & 40..think this is the last gasp ..

  26. A few developments to discuss…..

    I thought models showed the modified front/boundary stalling and dying out around Seattle…. It’s moved south of Tacoma with temps falling to 31-34 between Chehalis and Olympia with a N-NE wind shift. It is still apparently moving south. Interesting. They did show we were to cool off aloft at 850mb and a somewhat at 925mb from the northwest, and we have done so, but at the surface no model showed temps falling throughout the day to the low 30s as we’re definitely seeing to the north of Kelso now. Seattle is down to 29. What does that mean? Models apparently didn’t handle the arctic trough very well and how it dug south out of British Columbia. It is likely digging further south giving support to drive the Modified Arctic boundary likely to move through PDX and maybe down to Salem. If I am right this means our temps will fall in PDX metro into the low to mid 30s before 3-4 PM. That was not forecast.

    IR 2KM sure seems to show the arctic trough digging due south down the Washington Coast.

    Loop – http://sat.wrh.noaa.gov/satellite/alternative.php?wfo=pqr&area=west&type=ir&size=2
    This was not forecast.

  27. That band over kelso long view came down from Seattle might be worth watching.

  28. Muxpux (Castle Rock 175') says:

    Nice moderate graupel/snow shower moving through kelso Longview. In the last 10 minutes, temp has gone from 40 to 33. And there is some sticking

  29. Longview 400 ft says:

    The arctic front is passing through. From 38.1 to 33.1 in 10 minutes and snowing with extras at times with the snow.

  30. It was most definitely a sleet / snow mix in SE about 10 minutes ago.

  31. Is it just me or does anyone else want a big snowstorm then call it good?

  32. Anybody know if it snowed in Seattle?

  33. JFB SE PDX says:

    Couple little bands of heavy graupel just dumped through inner SE. Pretty sure I caught some snow mixing in!

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