Lots of Sun This Week; Long Range Forecast Mess Too

We have a challenging long range forecast (still!) this afternoon…that would be an understatement. But first, the shorter term.

A weak cold front is moving through the region now, headed off to the southeast.  Not much rain with this feature this evening.  Then we gradually clear out on Tuesday.

Tuesday night, colder high pressure slips east of the Cascades, giving us a round of strong east wind through the Gorge and out into the eastern side of the Portland Metro area.  Previous model runs were a but stronger with this, but the WRF-GFS cross-section still shows 40kt speeds above the surface at PDX Wednesday morning (where it says 11/12, that’s January 11th at 12z, or 4am).

Windspeed in the western Gorge should be similar to the last event…lots of gusts around 60 mph, with 90 or so at Vista House during the day Wednesday.  Possibly Thursday too, but the wind dies down quite a bit Friday at the latest.  This surge of east wind will be cooler than the last as well.  High temps, even with the sunshine, will only be in the lower 40s in the metro area Wednesday.  The dry air and clear skies mean wind-sheltered areas (Hillsboro!) will drop down around 20 Wednesday and Thursday nights.  The chilly December weather is coming back for a few days.

Friday and Saturday look uneventful, especially on the GFS and ECMWF models.  Just a return to onshore flow and dullness; probably dry.

So where are we with possible colder, wetter, or snowier weather? 

We can probably rule out only one thing right now; it’s unlikely we’ll see any sort of big arctic blast through the 6-8 day period.  

Just about everything else is still on the table Sunday and beyond.  That would be:  mild and dry next 10 days, or wet snow to sea level in very cold onshore flow, or possible windstorm next week, or just cooler and wetter with no valley snow but lots in the mountains.

The GFS model (NOAA’s long range forecast model) continues to stubbornly insist we’ll stay mainly dry and mild through the foreseeable future.  Here is the 18z (latest run) GFS ensemble chart.  Note the operational run is clearly way up in the “warm area” if you go out to about next Monday.  Check out how many of it’s ensemble members are significantly colder, some as early as Saturday night.  By the way, the Canadian model is showing snow near sea level as early as Saturday night too with an upper-level trough digging south more rapidly than the GFS.

Now check out the 12z ECMWF ensemble chart:   

Some nice info can be gleaned from this one.  The ECMWF operational model has a strong cold front moving through here on Sunday, with temps cold enough Sunday evening to bring snow down into the hills.  Precipitation tapers off Sunday night, so not a big deal anyway, but still, quite a change to cooler and wetter weather.  But look at the chart above, I notice it’s right in the middle of it’s ensemble members, so quite supportive of itself I guess you could say.  Note the large number of ensemble members that bring in the cold a day earlier, much like the GEM and some GFS members.  This will be interesting to watch…could the timeline for the first deep trough move up a day?

So what’s my preference?  Totally undecided, I don’t think anyone forecasting lowland snow (or continuing mild and dry) is doing anything more than guessing; still far too much model indecision.  Up until today, the “change” has been outside the scope of our forecasting here since we just do a 7 Day forecast.  But it’s time to buckle down and we’ve chosen to go with the ECMWF, as I often do.  So our 7 Day forecast goes with it.  Very light rain or showers Sunday as the cooler air moves in, then drying out Sunday night and Monday ahead of a strong system Tuesday.  Precipitation is light at that time and 850mb temps are marginal for snow; combine that with the assumption that details will change with the next model run.  That’s why we don’t have snowflakes on the 7 Day forecast for Sunday night or Monday morning.

To sum it up; I have advised Wayne Garcia not to bother putting on his studs yet.  We MIGHT get through the next 7 days with no valley-floor snow issues.  He’s hoping he can make through the next 5 weeks without them.  After that he’s probably clear for the winter.  Hard to believe the bulk of the “snow season” has passed already!

9:30pm Update:  The 00z GFS just came in with no rain and mild through next Tuesday, then heavy rain the 2nd half of next week.  A pineapple-express type setup with snow only way up on the mountain.  Good news though, the 00z GFS ensemble chart shows it was just about the warmest member.  There could still be hope…maybe.  I especially like the ONE ensemble member that brings an 850 mb temp of -23 C. next Tuesday.  Here’s the chart:

Chief Meteorologist Mark Nelsen

166 Responses to Lots of Sun This Week; Long Range Forecast Mess Too

  1. There will be something other than just plain old rain in the next 2 weeks or so!

  2. peter says:

    I’m going to have to trust Bob on this one.

  3. Bob says:

    The 18z GFS ensembles are colder than the operational, say hello to snowstorm…… I’m confident PDX metro will see atleast a moderate snowstorm with a good chance of a major one. 🙂

  4. Leroy says:

    Check out new NWS discussion:

    .LONG TERM…LARGE SCALE CHANGES IN THE WEATHER PATTERN ARE EXPECTED
    TO BEGIN OVER THE WEEKEND AND CONTINUE INTO NEXT WEEK. THE HIGH
    PRESSURE RIDGE WILL FINALLY BREAK DOWN AND SHIFT EAST AS A STRONG
    UPPER TROUGH DEVELOPING IN THE GULF OF ALASKA DIVES SWD TOWARD WRN
    WA ON SATURDAY. THIS TROUGH AND INITIAL FRONT IS EXPECTED TO USHER
    IN A MUCH COLDER AIR MASS ALONG WITH WET WEATHER AND MUCH LOWER SNOW
    LEVELS.

    ALL MODELS HAVE COME INTO FAIR AGREEMENT THIS AFTERNOON WITH THE
    GFS/ECMWF/CANADIAN/AND UKMET ALL DEVELOPING A COLD AND VIGOROUS
    UPPER TROUGH OVER THE AREA LATER THIS WEEKEND. THE LEADING SURFACE
    FRONT WILL MOVE THROUGH WESTERN WASHINGTON SOMETIME SATURDAY OR
    PERHAPS SATURDAY NIGHT. THE UPPER TROUGH TO FOLLOW WILL SETTLE OVER
    THE AREA FOR SEVERAL DAYS. MOST MODELS INDICATE RAPID
    COOLING…ESPECIALLY ALOFT WITH SOME MODELS SHOWING 500 MB TEMPS
    DOWN BELOW -40 C. MID AND LOWER LEVELS ALSO COOL BY SUNDAY WITH 850
    MB TEMPS IN THE -7 TO -10 C RANGE. THIS INITIAL BLAST OF COLD AIR
    MAY BE ENOUGH TO DROP SNOW LEVELS TO NEAR SEA LEVEL.
    HOWEVER…MODELS OFTEN OVER DO THE EXTENT OF COLD AIR SO THERE IS
    ENOUGH UNCERTAINTY TO KEEP THE PRECIPITATION TYPE MENTIONED AS A
    RAIN OR SNOW SUNDAY AND INTO EARLY NEXT WEEK.

    THE PATTERN BECOMES SHOWERY EARLY NEXT WEEK WITH A COLD AIR MASS
    OVERHEAD AND EVEN COLD AIR DAMMED UP ALONG THE CANADIAN ROCKIES
    READY TO SPILL IN GIVEN THE CORRECT CIRCUMSTANCES. GIVEN THE STRONG
    SURFACE HIGH PRESSURE THAT ALL THE MODELS SHOW OVER SRN B.C. IT
    SEEMS LIKE A GOOD POSSIBILITY THAT OUTFLOW WILL USHER IN SOME OF
    THIS COLDER LOW LEVEL AIR INTO THE N INTERIOR AND THE STRAIT. ALL OF
    THE LOWLANDS COULD GET QUITE COLD BUT GIVEN THE EXTENDED TIME FRAME
    I WILL OPT TO TREND TEMPS DOWNWARD INTO THE LOW TO MID 30S…BUT
    HIGHS IN THE 20S IN SOME AREAS ARE NOT OUT OF THE QUESTION IN THIS
    TYPE OF PATTERN.

    ALL OF THE ABOVE MENTIONED GLOBAL MODELS AGREE ON UNDERCUTTING OF
    THE RIDGE BY TUESDAY OR WEDNESDAY. THIS COULD INJECT SIGNIFICANT
    MOISTURE INTO A VERY COLD AIR MASS WHICH COULD GET QUITE MESSY.
    HOWEVER…THERE IS AN EXTREME AMOUNT OF DETAIL INVOLVED IN
    PREDICTING LOWLAND SNOW AND IT IS SOMETHING TO SIMPLY KEEP AN EYE ON
    THE NEXT SEVERAL DAYS. MERCER

  5. Kyle says:

    I have a serious question about the models:

    What will the scenario be if both models wind up being right which we have extreme cold air and tropical moisture coming at the same time?

    Both models show two different solutions so what if they are both right with cold air and tropical moisture.

  6. stevied (North Portland) says:

    18z… at face value for PDX..

    Brings cooler air in Sat. night/Sun morning
    Possible surface level snow showers Sunday
    Slow moderation begins Monday with light rain showers
    SLIGHT possibility it’s cold enough for a brief transition event on Tuesday.
    Then seasonal and rainy.

    Nothing to write home about. EURO and GFS are aligning now and both showing a very brief and only moderately chilly “event” now. Still a little time for this to adjust. Honestly, just a BIT more southward progression would mean the following incoming storms would likely be snow/ice for PDX. We shall see.

    • JohnD says:

      Sometimes I wish that I wasn’t such a blog
      addict this time of year. And talk about
      diversity in views-interpretations! If you
      take the NWS AFD (just issued) literally at
      ALL there IS reason for optimism! What the
      heck?! O.K. this is what I THINK!: 5 days is
      an eternity when it comes to potential winter
      weather. We will just have to wait and see
      if the weather gods are smiling on us or not!

    • john says:

      whats the 18z doing for the Olympia area

    • Joshua in Lake Oswego says:

      Skipping right over you and bringing everything directly here. Just kidding. I think the further north you are, the better your chance for snow. We will all likely have plenty of precipitation starting sometime next week.

  7. PaulO says:

    To my untrained eye the early portion of the 18Z GFS brings the cold air in about a day sooner. Upper air pattern does not look good for long-term cold though but that is a ways out.

    • Jethro (Canby ~187') says:

      The 18z GFS would bring nada for cold air and snow, but it would definitely be *active* — 5 separate lows in close succession in close enough proximity to impact our weather. If there was arctic air east-side, or if the lows took a more southerly track, there’s a chance they could pull cold air through the gorge and give us a brief snowy surprise.

      The main thing is that it continues the trend to colder and more active weather, even if this particular run doesn’t deliver the goods.

  8. Bob says:

    The new 18z GFS, all I can say is WOW! 🙂

  9. pappoose in scappoose says:

    “this pattern may result in significant snowfall across much of the area”

    National Weather Service Portland or
    217 PM PST Tuesday Jan 10 2012

    Long term…the latest extended model runs continue to keep an
    upper level ridge through early this weekend. The pattern looks to
    change significantly late Saturday into Sunday. Models are just
    beginning to show slight agreement on a deep trough digging down over the Pacific northwest from over British Columbia through the weekend and into early next week…potentially significantly
    dropping snow levels over much of the area. This trough does also
    bring precipitation beginning Sunday…with a second potentially wet
    system moving across the area Monday into Tuesday. Depending on the strength of the trough and eventual extent of the cold air…this pattern may result in significant snowfall across much of the area to begin next week…especially into the Cascades and foothills. Although details with this change are still quite fluid…it is a
    situation that bears watching closely over the next few days. Brown

  10. Kyle says:

    What amazes me is with this mild winter for the ENTIRE USA as well as Europe that the global warming alarmists aren’t coming out in droves doing their usual trash talk to the *deniers* that are SO evil and greedy. 🙂

  11. If anyone is interested in good, weather-only discussion on Facebook, I have started a new group. http://www.facebook.com/groups/215674491854669/215676621854456/?notif_t=like

  12. Brad says:

    The GFS giveth and the EURO taketh away?

  13. Mark must have phoned in a new 7 day… shows “mixed showers” and high of 38 for Monday.

    • Ryan (Walnut Grove) says:

      No real reason to think otherwise at this point with the GFS beginning to turn to colder but the EURO backing off.

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