Merry Christmas; Stormy End to 2011

It’s back to work for me this evening.  A nice slow time to get all those important Christmas Day items in order; mainly making 2012 vacation requests (a priority!), clean up emails, and get back into the meteorological groove.

Most of our region hasn’t seen more than a few hundredths of an inch of rainfall for about a month now.  In fact it was Sunday 4 weeks ago the last time we had more than .04″ here in Portland.  Today was a pitiful .05″ officially at PDX.  Ignore the .06″ below at PDX…it miscounted .01″ this morning when it was dry:

There is Good News and Bad News in this week’s forecast:  the dry spell is going to come to a quick end this week would be the good news.  And for storm lovers it appears we’ll see two very strong systems coming inland.  The bad news?  The biggest week of the ski season for the ski areas is going to feature heavy rain for about a 24 hour period, even at the higher resorts, from later Tuesday through Wednesday night.

IF YOU PLAN ON SKIING THIS WEEKChoose Monday, Thursday, or Saturday/Sunday.  Forget about Wednesday and Friday, and Tuesday will be a wet snow at best, more likely rain below 5,000′.

The big picture shows a strong westerly jet stream, the first in a month, punching right into the Pacific Northwest.  Several strong waves and their associated deep surface lows move by to the north.  The strongest is later Tuesday and Wednesday, but the low is so far north that we end up in the wet and warm sector south of the low.  We’ll be in the 50s during this period (regardless of the time of day/night) with gusty southerly wind west of the Cascades.  The low pressure center is far enough north that we’ll see gusts stay below 45 mph here in the western valleys of Oregon/Washington.  The snow level goes way up during the day Tuesday, at least up to 6,000′ by sunset, then even higher Wednesday.  Then we get a break Thursday.

The Friday surface low is deeper and tracks closer to us…00z GFS show it hitting the central or southern part of Vancouver Island.  It’ll be very interesting to see what the ECMWF does with the system.  Any closer to us or deeper and we’d see southerly wind gusts over 50 mph here in the metro area.  Once again, as the warmest air mass passes overhead with this storm, snow levels will jump up to at least 5,000′ sometime between late Thursday and late Friday.  This is the system I’m watching most closely this week.  10:30pm update:  Ohhh…that 00z ECMWF is even deeper, fast moving with big pressure rises behind, and makes landfall just off the NW tip of Washington…the plot thickens a bit.  This would be a signficant windstorm north of Portland or possibly here as well.  Two items grab my attention here:  6 hours later the pressure has jumped 20 millibars over Portland; a big surge behind the low from the south/southwest.  And 16-17 millibars surface pressure gradient from Eugene to Olympia.  A common guess for peak south wind gusts in the Portland metro area is 3.15 x EUG-OLM gradient.  That’s 50-60 mph here. 

Looking farther ahead…who would have thought that in a La Nina winter, we’d have a month-long dry spell followed by a week or 10 days of warmer than normal systems moving through.  Upper-level heights remain quite high through the first few days of January, so after a break over New Year’s Weekend, more mild storms move inland next week.

Check out the 00z GFS Ensemble forecast of 850mb temps.  Note the ensemble average (red line) is for warmer than normal 850mb temps most of the time through the next 7-10 days, then a bit cooler after that time.  What I don’t see is a big blast of cold air or low elevation snow as we head into early January.

Chief Meteorologist Mark Nelsen

49 Responses to Merry Christmas; Stormy End to 2011

  1. Steve says:

    Mark any up dates on storm Friday?

  2. Runrain says:

    Temps here in Las Vegas looking to be 12 deg above ave this week (66-68). Normal high is 56. Low 70’s back in Phoenix but thats not unusual.

  3. eflow says:

    Thanks Mark, it was worth a try…

  4. eflow says:

    Mark, where can one find the GFS Ensemble 850mb Temperature time-series you often show?

  5. WEATHERDAN says:

    Discussion/Forecast: La Niña (cooler-than-normal tropical Pacific Ocean sea-surface temperatures
    “SSTs”) has returned. Global weather patterns never stopped being affected by last winter’s strong
    La Niña. Computer models are showing La Niña lasting at least through this winter.
    Outlook for this winter…It is looking likely that we will have a second straight winter of La Niña
    conditions. Historically, the second of back-to-back La Niña winters does not bring as much rain
    and mountain snow as the first. However, most mountain snowpacks should finish the winter
    season above average.
    The odds favor overall below normal temperatures and above normal precipitation. The chances of
    both extremely mild and/or cold episode(s) are elevated, with the likelihood that any extreme cold
    periods will be accompanied by significant western valley snow and/or freezing rain.
    The Following predictions were based on historical weather data from the January – March
    periods in 1972, 1975, and 2009.
    • A mix of stormy and placid periods with possible large temperature swings.
    • Mountain snowpacks should finish above normal, especially in the Cascades.
    • Increased chance of “extreme weather events” (record cold/warm, valley snow, wind, etc.).
    • Elevated chance of cold air outbreaks accompanied by valley snow and/or ice.
    Purpose: To provide Oregon farmers, growers, and forest management personnel advanced notice
    of potential significant weather events and climate trends, during the upcoming season, in an effort
    to enhance environmental, economic, and community stability.
    Basis of Forecast: Changes in sea-surface temperatures (SST) in the tropical Pacific Ocean have
    been closely linked with subsequent changes in world-wide weather patterns. By comparing the
    current tropical SST structure (including its recent evolution) with patterns from former years, best
    matches (subsequently referred to as “analog years”) can be identified. Historical weather data,
    from these analog years, is closely analyzed to help develop this climate forecast.
    Limitations of Forecast: Pacific Northwest climate trends are more pronounced during the “cold
    season,” especially during El Niño (warm) and La Niña (cold) events. The resultant weather pattern
    “types” are more identifiable and affect the local climate in consistent ways. Long-range climate
    forecasts are fundamentally different from short-term weather forecasts (the latter are derived from
    dynamic computer models). This forecast is not a climate model, nor does it use climate models.
    An assumption is made that “no climate change” has occurred between the analog years and
    the current year. Since our climate is constantly changing, that assumption adds a degree of
    error to the forecast.
    Pete Parsons – Meteorologist – Oregon Department of Forestry
    (503) 945-7448,

  6. W7ENK says:

    Woo hoo!!! I like vigorous frontal systems! 😆

  7. WEATHERDAN says:

    74 days until daylight savings time begins. 51 days until MLB spring training begins. However until then I want snow and cold. You can keep the high winds though. Happy New Year.

  8. N3EG says:

    No arctic blast this winter? I’m just fine with that. No snow either? Added bonus. Now if we can just get winter to end before June…

  9. vinnybob says:

    For cold ythat is.

  10. vinnybob says:

    The 06 and 12 look much better long range.

  11. Latest models have backed off the windstorm today.

  12. PaulB/Eugene says:

    Wind scenario reminds me of Jan 90…lived in Seattle at the time, missed the winds PDX got

  13. alohabb says:

    Let the excitement begin….winds or no winds….what will be the outome???? Sure would be interesting to have to pick up my rickity old fence and trees and we head into the new year!

  14. With the again weak gradients and clear skies, managed to dip to 28 last night and there is fog now. Some areas on the roads are very icy! Took it slow on the drive this morning!

  15. Kyle says:

    I do not see how the forecast low of 40F equals to above pass snow levels.

    40F I think would put the snow levels between 3 and 4K.

  16. Kyle says:

    The big reason for the lack of cold? Blame it on the AO!

    • W7ENK says:

      That’s one of at least a dozen and a half factors, Kyle. Our weather here in the PNW is more closely tied to what’s going on in the Pacific, so things like PNA, PDO and (to a lesser degree, perhaps) ENSO have more bearing and should be better indicators, but yes, everything is interconnected…

  17. bgb41 says:

    12/25/2011 Oregon (All) Temperature Summary

    High:58 at CW5984 Pilot Roc(1749 ft)
    Low: 23 at WEST BIRCH CREEK(1626 ft) & BROOKINGS(79 ft)

    High:28 at HARL BUTTE(6071 ft)
    Low: 0 at RED BUTTE (4460 ft )

    Largest Diurnal Change: 47 degrees
    CHRISTMAS VALLEY (51/4) (4360 ft)

    Heaviest Rainfall:
    0.73″ at DW0237 Lees Camp(699ft)

  18. Already had wind event today in the puget sound, peak gust in the 40’s to 50’s, even 60 mph at Alki. 49 on my rooftop

  19. Mark Nelsen says:

    Very interesting 00z ECMWF, much closer to windstorm status on Friday here…hit refresh on my posting…I updated.

    • W7ENK says:

      Well, at least that (new) part is exciting!

      We’ll see how it all shapes up in another 5 days…

    • Mark Nelsen says:

      The 00z Canadian has the low coming right over the top of us, but about 995 millibars (weaker). Interesting that they are all keying in on SOME sort of deep low moving SOMEWHERE close to us. And they all have it at the same time…Friday. I’d like to see the 12z GFS and ECMWF come in with a 970 mb low from Tillamook to Ellensburg. Maybe a nice 17 millibar gradient again, but ALL between Portland and Eugene???

    • Heading to Rockaway on Friday…hmmmm, any timing in your mind yet Mark 🙂
      Yes, i expect you to nail this down 5 days out!

    • W7ENK says:

      O_O You’re a sick, sick man, Mark! 😆

    • Mark Nelsen says:

      Seems to be during the day. Peak wind would have already hit the Coast well before the 4pm time shown on the ECMWF. Of course it’s one model run on one model 100 hours out…

    • Looks even more promising for western/north-central WA state….

    • Derek Hodges says:

      Lets get it a little deeper Mark just to make sure its really exciting.

    • Josh in Puyallup says:

      Mike. LIving in Puyallup, I often have to do double takes on the models after reading a post from Mark. I often forget that the weather between Seattle and Portland can be very different at times.

      But don’t worry Mark, I enjoy your stuff more then Scott Sistek or Cliff Mass. Both are smart and know what they’re talking about. But I’m pretty sure you hold the trump card.

  20. o.c.paul says:

    Wow. We don’t even need to use new year numbers for the Jan-March weather. Just call it, ‘2011 Redux’.

  21. W7ENK says:

    YAY! New post! 🙂

    Sucks for us ski bums, tho… 😦

  22. Well, any change is welcome to me. I would love an epic winter up there where they can’t even open the alpine slide until Labor day….

  23. Aleta-West Gresham says:

    Weather in general has just been odd for the last while! Here’s hoping for A LOT more mountain snow!

  24. Aleta-West Gresham says:

    Thanks Mark!

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