Winter Storm Watch Thoughts

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After all these days, we finally have an agreement in the models for the critical Tuesday night through Wednesday forecast.  I’ve put in a slide show which takes the ECMWF, GEM, GFS, & NAM for 18z (10am) Wednesday on the same map projection.  Note that they all are much closer on a surface low moving up against the Oregon/Washington Coastline by Wednesday morning.  The NAM has finally turned warmer with 850mb temps in the -7 to -8 range tomorrow, although that’s still slightly colder than the GFS/ECMWF.

So what does it mean?

1. The National Weather Service has issued a Winter Storm Watch for much of Northwest Oregon and Southwest Washington for this storm.  I think that is a little much, but they do need to err on the side of caution since that’s their job.  Probably a good move since  it’s only a WATCH, not a WARNING.  That means if it becomes obvious there is only rain coming in the lowlands, they can just change it to a Winter Weather Advisory for the hills.

2.  All of these models are very marginal for snow here in Portland, especially the GFS.  That said, even the ECMWF/GFS 850mb temps around -4 to -5 with 6-10 hours of easterly flow could change us over to snow.  Note the 12z WRF-GFS sounding for 1am Wednesday morning.  That’s REALLY close to snow.  Most important, I told myself I wouldn’t make the “December 29th mistake” again.  When it’s marginal, I’m going to tell the public so instead of just taking them along with my “weather gambling forecast” they can be prepared in case I’m slightly off.

3.  Due to that, I think it will probably not stick Tuesday night and Wednesday morning for most of the metro area, but it’s going to be very close!  Luckily it should happen mainly at night too.  And this forecast is subject to change the next 24 hours if models come any farther south with the surface low.

Where could we get significant accumulation of snow?  The central/eastern Columbia River Gorge (10″+ possible).  Longview and northward in Southwest Washington (4″+), and the western parts of Washington/Columbia counties, and maybe Scappoose/St. Helens too.  A little bit of the “Forest Grove Effect”, where cooler air pools up against the east side of the Coast Range.  Those spots could see 4″+ as well.

Quick warming on all models Wednesday afternoon.  A south wind with 850mb temps above zero is 50 degrees easy.   Gusts could be over 40 mph depending on the low placement.  Interesting to note the NAM-GFS from UW is much stronger and farther south with the low than NOAA’s version of the NAM.

Oh yeah, as for the next 24 hours, I haven’t changed my thinking much:

REST OF TODAY:  Snow showers pick up later…increasing southerly wind lifts sticking snow level up around 1,000′.  Highs near 40

TONIGHT & TUESDAY A.M. COMMUTE:  Snow showers, snow level doesn’t lower much below 1,000′, so 1-2″ new on the hills closer to 1,000′ and above.  No freezing in the lower elevations.  That’s because of the mild southerly wind continuing to blow.

TUESDAY:  Mixed rain/snow showers all day, sticking snow only up around 1,000′ or even a little higher by afternoon…1-3″ on the higher hills only.

Chief Meteorologist Mark Nelsen

358 Responses to Winter Storm Watch Thoughts

  1. Cliff Gavic 1,100 ft says:

    4.5 in moderate snow

  2. awesomeO says:

    Interesting. The NWS says that the area 3 miles NNE of King City in zip code 97223 will get a trace-1 inch of snow while 3 miles S Cedar Hills in zip code 97008 will get 2-4 inches of snow. The zip code of 97008 covers Beaverton city center almost up to Washington Square Mall while the zip code 97223 covers the area around Highway 99W on the border of Portland and Tigard. Didn’t think there was that much of an elevation difference between the two areas.

  3. Wendy-Silver Lake says:

    Temps going up slightly here. We’ve got south winds, but it’s also snowing, so I guess it could be either one causing it.

  4. Chris says:

    Why is it that the forecasts by The Weather Channel are incredibly off? They are still showing about 8 inches of snow during the next two days in the Portland metro area.

  5. 33 here now for quite a while. Been snowing steadily since 5pm & have an additional 2″ for a total of 4″ elev about 650′

  6. 33 here now for quite a while. Been snowing steadily since 5pm & have an additional 2″ for a total of 4″ e,ev about 650′

  7. Forest Grover says:

    Another good dusting before bedtime….hopefully it can slowly build over night again. Current temp is 32 degrees and creeping lower.

  8. Brad says:

    Tower temps continue to rise…turn out the light folks the party’s over….for tonight.

    We’ll see what tomorrow night’s low brings.

  9. TAGinGresham says:

    So at this point do the next few model runs matter or is it happening in real-time now? Do we still have a chance of things changing in our favor, and if so what would we need to happen?

    • EA_TTD says:

      In a word, no. Looks like a lock for some snow overnight tonight/tomorrow morning and then a quick burst of heavier snow overnight Tuesday. It’ll be a distant memory by Wednesday morning as the southerlies really kick in aloft. In fact, latest GFS shows 70 knot southerly winds at about 1000 feet midday Wednesday.

    • AdamInAumsville says:

      I want snow and then a windstorm!

    • EA_TTD says:

      TAG, a quick pointer. Go outside now and feel the wind. It’s out of the south which is a killer for snow here in the valley; always has been and always will be. Here in Troutdale, it’s gusting to 20 mph. No way we get colder tonight with that. Just trying to help as you seem genuinely enthused about the weather.

    • TAGinGresham says:

      Thanks you Eric! I would like to see everything covered at least for a few hours, but that may not even happen. However, I am not at all bummed because we have finally gotten into an exciting weather pattern, and it’s only the middle of January. I am hoping Dewey’s instints are right for the end of the month.Feb. Thanks again, I guess we will know soon enough!

    • EA_TTD says:

      I think he is. All that cold air in western Canada has to bust loose sometime and there are a lot of experts who say late January and early February is our time. We’ll see. Winter is far from over.

  10. Brad says:

    Watching the 10 o’clock right now….sad. They’re talking as if the roads are all iced up right now. Waiting for Mark to come on to give all the nonsense a hard dose of reality.

  11. Tigard 225' says:

    I know it isn’t going to freeze tonight but we are getting ever closer here at 33 F

  12. timmy - scappoose says:

    Wow, it looks like we may see a little more snow in the area before wednesday morning. But Seatlle and N Wa. are going to get epic record snowfall. I could honestly care less about them, I am just mad that with a slight shift, we could have gotten clobbered. This will be the event that could have been.

  13. jerry says:

    Someone have a link to the blog without the ad and banner?

  14. I have one question:

    Are the drugs these guys taking legal?

    Ripped from the NWS Forecast Page for the location of my house in Salem

    Tonight: Snow showers. Steady temperature around 36. South wind between 13 and 15 mph, with gusts as high as 20 mph. Chance of precipitation is 90%. Little or no snow accumulation expected.

    Tuesday: Rain and snow showers. Snow level 300 feet rising to 800 feet in the afternoon. High near 40. South wind between 11 and 13 mph. Chance of precipitation is 100%. Little or no snow accumulation expected.

    Tuesday Night: Rain and snow, becoming all snow after 10pm. Steady temperature around 36. South wind around 10 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible.

    Wednesday: Snow before 10am, then rain. Snow level rising to 7400 feet. High near 48. South wind between 13 and 21 mph, with gusts as high as 24 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible.

    Either that, or they’re trying to be funny like I was earlier.
    Sorry guys, mine was funnier

  15. sounds like everyones on the ledge about to jump. just a quick reminder, a few days ago this was headed to vanc island and everyone up and down western washington was getting rain. if it could change one direction and can always change back, a lot of our bigger events have been surprises.

    • EA_TTD says:

      Anyone who thought this was a lock or is on a ledge about to jump hasn’t been paying attention. This ‘event’ was never certain, especially for us down here. They’re overrunning the grocery stores in Seattle however….

    • robwaltemate says:

      Stranger things have happened before! Haha.

    • pappoose in scappoose says:

      Rare for us to have a guaranteed snowstorm. I’m gonna break out the GOLU model, kick back, and enjoy the ride. Anything can still happen. Flip/flop/flip/flop. Fish outta water! Hahaah!

  16. john says:

    i dont understand im watching the radar and every huge snow cell brakes apart before reaching my house it would be fine but every one for the last hour has been during so i live in puyallup by graham and i dont know why if you know please tell me thanks and if theres a term for it that would be nice to know

    • EA_TTD says:

      They’re called the Olympics. They’re mountains to the west of you and when they get real hungry, they eat everything in sight. They especially love snow showers that are headed for the valley.

    • Marcus, loves snow! in La Center says:

      CAN THE COAST RANGE STOP EATING ALL OUR SNOW GRRR!

    • robwaltemate says:

      I think it may have something to do with the fact that they are showers and once they start to precipitate they just run out of moister. Are there hills to the West of you? Maybe a rain shadow effect? I’m just guessing here… I build houses for a living. LOL

    • john says:

      ok thanks will the wind or direction of the showers turn so i will get snow

    • EA_TTD says:

      Up there you may get a more northerly component which would bring precip down the Strait. Failing that, you’ll need heavier precip. If you’re in Puyallup, you’ll get all the snow you want and then some tomorrow night and Wednesday.

    • john says:

      last question when is that front going to reach here

    • EA_TTD says:

      Overnight tomorrow night….guessing you’ll see some impressive sights up there around 2:00 Wednesday morning and it won’t let up for awhile.

  17. robwaltemate says:

    Had about 1″ of snow yesterday, and not all of it melted, so today in the morning had almost another inch. All told today the kids had almost 2 inches of snow. Last night was cooler and there was black ice everywhere by 7pm from here (NNE of Long Beach, WA to Warrenton, OR).

    All the showers are now moving to the Northeast, where yesterday they were moving Southeast. Some of the showers were developing right off the coast here.

    Tonight we haven’t seen much weather; most of the showers are headed to Gray Harbor area so far.

    Right now temp is 34.5 F and the high today 39.1F and I bet downtown Long Beach was 40! DP 31.7 F (RH 90%) and calm. Pressure is 30.04 “Hg.

    I know NWS was saying up to 2” below 500 ft near here, but with the ocean so close I’m not so sure unless the upper air is really that cold.

    Mark, was this the first or last book end for our La Nina winter?

  18. New 00z WRF-GFS 12km x-section out…
    http://tinyurl.com/89vlv79

    This would indicate 1am-5am early Wednesday morning would be last chance for snow before south wind kicked in and we got a big warm up. Showing light easterly wind during that time-frame though, so I’m thinking it will be a very quick transition. Also, note that from here on out, we have onshore flow above 925mb — and only that brief time period of light east wind (below 925 mb).

  19. Jerry says:

    Anyone seeing snow or just a mix/rain?

  20. john says:

    i dont understand im watching the radar and every huge snow cell brakes apart before reaching my house it would be fine but every one for the last hour has been during so i live in puyallup by graham and i dont know why if you know please tell me thanks

  21. vinnybob says:

    If eastern Oregon doesn’t have any cold air Tomorrow, I don’t think east winds really matter, although they might help enough.

  22. germantownsummit1000' says:

    Still snowing…

    31.4

    3″ and counting.

    • No snow says:

      I was just on Germantown/Skyline. It is 34 degrees and just a dusting on the sides of the road. The roads are bare pavement.

  23. 925 mb temps are above 0c by 7 AM Wednesday on the GFS. That is about 2,000′.

    NAM shows 4 AM.

    In fact, I don’t see hardly any east wind either.

  24. Don’t forget, the low hasn’t even formed yet, and all we are basing it’s landfall upon are computer model estimates. This thing could go 200 miles north or south of where currently projected…technically, every possibility should still be on the table. just sayin’…

  25. WhiteEagle - Garden Home/SW Portland says:

    My humble opinion, for what it’s worth:

    Mark did the right thing. He didn’t sensationalize and trusted his instincts. He is a great forecaster and still may be right about this one. Another thing that’s great about Mark is that unlike a lot of us (myself included sometimes), he’s not too stubborn to change direction when he sees fit.

    Keep up the great work, guys!!!

  26. PaulB/Eugene says:

    Looking at models…south valley..central valley…north valley look done for snow with this episode, at least at valley floors. If the models are terribly wrong and the low tracks due E over middle of Oregon then it could be different…but I see no evidence at this time of this happening…PDX will be right on the edge…..if there is model error in our favor then of course PDX would be the first to benefit from it.
    As for Puget Sound…amounts still look decent but model projections look a bit less this time around. That does not mean they may not get big time accumulations. It could still happen. There will be some surprises in the next 48 hours.
    The mid/higher elevations of Cascades will get hammered with snow. Willamette Valley total precip in the next 5 days could be in excess of 4-5 inches (over 10 inches liquid possible in Cascades, S/central oregon coast range).

    • AdamInAumsville says:

      Thanks for the input, Paul.

    • WhiteEagle - Garden Home/SW Portland says:

      Thats the one sure thing Paul…there WILL be surprises. 🙂 Looks like a tough night for snow lovers in Eugene though. 😦

    • The good thing is, we are finally in a good winter pattern after the fog-stagnation of the last month. So lots of goodies to come. I still think a pretty gosh darn windy period Wed-Fri. and then back to mtn. snows. Looking for a late Jan. early Feb arctic blast.

  27. WhiteEagle - Garden Home/SW Portland says:

    00z GFS – Not bad!!!! Could we possibly have the ying-yang effect in the Valley, where Southerly flow blasts north into Aurora but northeast wind keeps the snow going in Forest Grove and McMinnville?

  28. Roman~Snow-Zone says:

    Nice snow shower here in Monmouth. Big flakes, temp has come down a bit, 33.4F.

  29. Brad says:

    New AFD:

    .SHORT TERM…DOPPLER RADAR SHOWING WIDESPREAD SHOWERS OVER THE FORECAST AREA THIS EVENING. EXPECT THIS TO CONTINUE AS FORECAST THROUGH THE NIGHT AND TUESDAY MORNING…SATELLITE IMAGERY SHOWS AN EXTENSIVE AREA OF COLD AIR CU OVER THE NORTHEAST PACIFIC MOVING TOWARD THE PACIFIC NORTHWEST. THE COLD UPPER LEVEL TROUGH MOVING OVER THE AREA WILL CONTINUE TO STREAM THESE SHOWERS OVER THE AREA WITH SNOW LEVELS FALLING TO THE SURFACE TONIGHT.

    A SHORTWAVE ROTATING THROUGH LATE TONIGHT AND EARLY TUESDAY MORNING
    WILL BRING A MORE ORGANIZED AND STRONG BAND OF SNOW SHOWERS INLAND
    WITH THE HEAVIEST PRECIPITATION BETWEEN 7 AND 10 AM. SNOW LEVELS AT
    THIS TIME WILL BE AROUND 500 FT…THOUGH HEAVIER SHOWERS COULD BRING
    BRIEF ACCUMULATIONS OF AN INCH OR TWO DOWN TO THE VALLEY FLOOR AND
    COAST. IN THE FOOTHILLS AND COAST RANGE SNOW ACCUMULATIONS OF 4 TO 8
    INCHES ARE POSSIBLE WITH HIGHER TOTALS IN THE CASCADES. SNOW SHOWERS
    WILL TAPER OFF SOMEWHAT IN THE AFTERNOON WITH STICKING SNOW LEVELS
    RISING TO 500 TO 1000 FT IN MOST LOCATIONS.

    THE IMPACTS FROM THE NEXT RATHER POWERFUL FRONTAL SYSTEM WILL START
    TUESDAY EVENING AS THE LOWER PRESSURE OFFSHORE STARTS DRAWING COLDER
    AIR FROM THE EAST SIDE. PRECIPITATION WILL SPREAD NORTH TUESDAY NIGHT
    AS A WARM FRONT LIFT FROM SOUTH TO NORTH BRINGING RATHER HIGH QPF
    AMOUNTS. VERY STRONG SOUTHERLY WINDS WILL ACCOMPANY THIS SYSTEM AS
    WELL WITH GUSTS OF 80 TO 90 MPH ALONG THE COAST AND IN THE COAST
    RANGE NOT AT ALL OUT OF THE QUESTION. DEPENDING ON THE LOCATION OF
    THE MODIFIED ARCTIC FRONT AND THE STRENGTH OF THE OFFSHORE FLOW THAT
    DEVELOPS THERE IS POTENTIAL TO GET A GOOD BIT OF SNOW BEFORE
    SOUTHERLY FLOW SCOURS OUT THE COLD AIR MIDDAY WEDNESDAY. GIVEN THE
    DEEP NATURE OF THE COLD AIR MASS IN PLACE CURRENTLY AND THE LACK OF
    A LARGE LOW LEVEL COLD POOL EAST OF THE CASCADES…IT LOOKS LIKELY
    THAT SNOW WILL TRANSITION OVER TO RAIN WITH A MINIMUM OF MIXED
    FREEZING RAIN OR SLEET TYPE PRECIPITATION. THE GORGE COULD BE AN
    EXCEPTION BUT BASED ON THE STRENGTH OF THE INCOMING FRONT ANY
    FREEZING RAIN THERE SHOULD BE BRIEF MAKING HEAVY SNOW AND STRONG
    WINDS THE MAJOR IMPACT. LIKENS

  30. andrew says:

    What a shame. Mark is right. Rain from here on out!!! No snow for PDX, NONE.

  31. Brad says:

    Tower temps continue to creep up. Snow level around 700-1000 ft now. Looks like Mark was right all along – at least about tonight.

  32. Bob says:

    This folks is the final nail in the coffin! The 00z GFS just gave PDX metro a huge snowstorm, followed by a big ice storm. Mark will have no choice but to change his forecast now…..

  33. alohabb says:

    The latest charts/graphs sure show a trend to MAJOR weather in PDX starting tomorrow. Tonight would be the calm before the storm!

  34. Tigard 225' says:

    Another thing that appears important to me is that there is a pesky low pressure area near Idaho that seems to mess up our gorge gradient a bit. I would think that that is an important issue

  35. Jeremy KF7NGT says:

    35.2 in SLE. I’m thinking this will be a PDX north event. All rain with some possible slush at the higher elevations here in Salem. I think we are at our coldest now. 37 or 38 by morning. Sorry kids, too much not cold air.

  36. Muxpux (Castle Rock 175') says:

    Whatever happens, the 4″ + sounds good for us trollololo

  37. You guys are working yourselves into a frenzy over what? At best it will be a few hours of snow, mostly in east county on Wed. Followed by rain. IMHO….

  38. Jonny B says:

    The temp and dew-point continue to rise, nothing but rain at 500′ here in the gorge. Not sure why there is a winter storm warning in effect starting at 8 tonight.

  39. Brad says:

    Really liking the 00z folks….has completely come around to the NAM. L slightly north of NAM but the trend is definitely south.

  40. Kyle says:

    I am willing to be the high of 40F is going to occur at between 12-4am and we all wake up to 37F tomorrow and blowing rain.

    No snow kiddos. :p

    • Ryan says:

      Very possible but the threat is tomorrow night when the low approaches and the east wind kicks in. Tonight and tomorrow morning is just showers. Watch the wind closely tomorrow!

  41. Andrew (Portland....Sylvan Highlands ~800 feet) says:

    Think Mark will make some major adjustments to his forecast tonight now that the 00Z GFS is showing a major snow event for the pdx metro area.

    • Josh (Gresham) says:

      Yeah Alot of debate going on about 00z… Pretty sure several social media platforms are about to crash around here hahaha

  42. SnowedIn - North Plains says:

    This whole situation seems quite familiar…..

    https://fox12weather.wordpress.com/2009/12/30/snow-storm-09-wrapup-what-happened/

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