Wet Weather Ahead; But No Sign of Lowland Snow/Ice/Cold

9pm Sunday…

It’s been 9 days since I last posted. Part of the reason (other than keeping busy at work) is the lack of stormy weather. As mentioned in the previous post this first half of December was looking drier than average. Sure enough…the 14 day anomaly across the western USA shows a very dry month SO FAR…

Temperatures have been running near average over the Pacific Northwest. Although wintertime inversions in some valleys/basins have given cooler than average (Pendleton, Tri-Cities)

Again, nothing too exciting. We had a pretty good easterly wind episode the first week of the month; Troutdale saw 7 consecutive days with gusts 35 mph or higher. That said, it is December and that sure isn’t unusual. We’ve seen snow in the central/eastern Gorge twice now, although real marginal both times… the 2nd was last night. I had a wonderful day of light rain showers with the temperature between 33-36 degrees all day long (at home). Snowpack IS running near average in the Cascades which is great news. As I write this I see Hwy 26 through Government Camp has turned snowy again

A couple of notes…nowadays I spend time putting out shorter thoughts/maps etc… on Facebook, Twitter. It’s much easier on a busy night to quickly post a model chart or other weather information there as opposed to a long blog posting. You can find me on Facebook as @marknelsenweather or Twitter as @MarkNelsenKPTV Also, we have a Northwest Weather Podcast. Lots of fun! Just this past week the four of us (Brian MacMillan, Jeff Forgeron, Anne Campolongo, & I) discussed La Niña so far, Vista House wind, Solar Eclipses, & holiday plans for the weather center. Several weather folks having a jovial conversation…what could be better? You can find it here: https://www.kptv.com/podcasts/weather/

What’s Ahead?

1- We are turning wetter now and should see more regular rainfall over the next 10-14 days. I don’t see a significant dry spell (2+ days) between now and at least the middle of next week.

2- There’s NO sign of real cold weather or lowland snow west of the Cascades for the next 10+ days. That bumps us up right against Christmas of course. My gut feeling is that we won’t be seeing snow anywhere near the lowlands for Christmas Week (next Sunday through Christmas Day).

3- I don’t see flooding or an especially stormy pattern for the next 7 days. Most of the weather systems moving inland are relatively week; I’m not seeing big deep low pressure areas in the eastern Pacific. Of course that could change, but not this week.

I can explain both #1 and #2 by showing you the 500 millibar forecast from the GEFS (GFS ensembles) for the next two weeks. 2 weeks in about 4 seconds.

It’s a continuing train of weather systems moving west to east in a “zonal” flow. That’s as opposed to a “meridional” flow which would lead to more north-south movement. Also notice there are no prolonged ridging episodes (dry weather). In this pattern it never gets cold because the chilly arctic air is bottled up to the north of the jet. You aren’t going to get lowland snow in this setup. Look at the 850mb ensemble chart from the ECMWF model. I’m amazed that through the entire 2nd half of December there are almost no members (each line is one of 51 ensemble members) that drop below -7. That’s about what we need for lowland snow in onshore flow. Very consistent westerly flow = mild.

Confirmation comes from the GFS ensemble forecast of Portland snowfall the next two weeks (through Sunday the 28th). Hardly a single member tries for 2″ or more snow.

There are hints that Christmas Week might be a bit drier than this week and coming weekend. You see quite a few more gaps in 24 hour precipitation totals during the 2nd week.

What About La Niña? Shouldn’t Weather Be Wilder at This Point?

No, not necessarily. Remember that La Nina doesn’t guarantee lowland snow, and it sure doesn’t guarantee lowland snow and stormy weather between November 1st and January 1st. For all we know, we’ve got crazy wild weather action coming in January or February! For fun I looked back through the last 10 La Nina winters to see what happened. Some start just like this…mild and dry-ish. My brief notes on each.

2017– A boring November, dry ridging 1st half of December. No decent skiing until Christmas Vacation

2016– Crazy and wild ride. At this point we had just gone through an ice storm and were preparing for a 2pm arrival (December 14th) of a snow storm. Everyone hit the road at the same time and you remember what happened. I always remember the date 12-14-16.

2011– Stormy November, Dry December. Then a big atmospheric river wipes out quite a bit of snow on Mt. Hood right after Christmas. January 2012 following was stormy

2010– Stormy November, arctic air at Thanksgiving

2008– Boring November, dry December start. Arctic blast arrives right about now (Dec. 14th). Two weeks of snowy mayhem followed…

2007– Boring/dry/mild November, huge coastal storm and widespread flooding just north/west of metro early December. A series of colder storms began in mid December bringing feet of snow to the foothills and many feet the rest of winter to the Cascades

2000– Nothing all that interesting, cold/dry November, in fact entire winter was dry-ish. Didn’t fit La Nina pattern at all

1999– Warm & wet November

1998– Very wet November and December, arctic blast around December 17th

1995– Warm and wet November, stormy December included the last major regional windstorm (12-12-95)

You can see this current year isn’t a very good fit for any the last 10 La Nina winters. Maybe similar to the last one 2017-2018? Interesting…

That’s it for now, enjoy the rainy weather. Best chance for some dry is tomorrow and maybe sometime between Thursday showers and renewed rain on Saturday…possibly Friday.

Chief Meteorologist Mark Nelsen

46 Responses to Wet Weather Ahead; But No Sign of Lowland Snow/Ice/Cold

  1. tim says:

    Today’s cpc december update has us cooler then normal this month which is false it’s been above norm temps so far.

  2. tim says:

    The cpc temp outlook seems too cold, i don’t think they consider the warm blob and or the positive pdo which would give us warmer temps.

    • Tanis Leach says:

      PDO recently flipped into negative, as noted on Pete Parson’s forecast. A weak negative PDO ring is also present in the SST.

      The blob is a fair reason to question though.

  3. Tanis Leach says:

    Today was the release of 2 other winter forecasts updates for those who want to see.

    Pete Parsons (ODF/ODA): https://www.oregon.gov/oda/programs/NaturalResources/Documents/Weather/dlongrange.pdf

    CPC: https://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=1

    Also, unrelated, has anyone seen 0z GFS, out 258 hours? Total clown range, but if I’m seeing it correctly, snow level 500 feet between Vancouver to Kelso. Salem to Eugene about 4000 feet. Just something to keep an eye on if it keeps this for like 4-6 major runs (0 and 12z).

  4. Joshua Lake Oswego says:

    Mark, your 7 day forecast is pessimistic even by my standards. Showers at time on Sunday is all the rain mentioned for the next 7 days?

    There is still a solid chance we get absolutely deluged late Saturday through Monday. There is a very good chance that we get a whole heck of a lot more than showers at times. What am I missing?

    • Matt in Keizer says:

      I just checked kptv.com and they have updated the 7-day to rain all day both Sunday and Monday which is what the models have been showing.

  5. Roland Derksen says:

    Definetly not drier than normal this December here in BC. This morning I had a glimpse of the local mountains: They are loaded with snow. So even if we don’t get much snow here down in the lowlands, at least we;ll have plenty of it where it’s needed.

  6. JohnD says:

    A bit of a cool down next week?! Hopefully a sustainable trend/precursor to a pattern change!

  7. JohnD says:

    Thanks much Tanis. Great stuff. Thorough and meticulously considered—professional quality. Here’s hoping that the kind of conditions evolve that we active weather enthusiasts long for!

    • Tanis Leach says:

      Your welcome. And thank you for the complement. If there is anything I can do to improve, please let me know.

  8. Patrick says:

    Mild is great, as long as the mountains get the needed snow. Keep this mild weather coming, maybe a stretch of dry weather , now and then.

  9. Tanis Leach says:

    Released Monday December 14th (posted 9 am the 15th): https://www.youtube.com/watch?v=04-5ZV3vEyY

    Updated winter weather predictions for those who want to watch. Skip to 10:18 for predictions.

    Due to technical issues with my microphone and video editing software (not shown), posted on my personal youtube instead of DAM weather.

  10. Mr T says:

    Just for a fact in 1941 this would be the last time a public forecast would be issued. https://news.google.com/newspapers?nid=djft3U1LymYC&dat=19411216&printsec=frontpage&hl=en

    Guess About The Weather and No Weather Map During War bylines:

    • Anonymous says:

      So interesting to read a 1941 newspaper!…..FYI the weather page Mr T refers to above is on P.33, also of interest an article about the U of Or. touring men’s basketball team on P.29, and on P.13 note the ad for a bran new state of the art washing machine for $84.95!

    • Tanis Leach says:

      I would not want to live then, but also fascinating. Thank you for sharing.

  11. Weatherdan says:

    Fzl at 9k.,Possible heavy rain this weekend. NWS PDX says flooding possible then as well. Maybe coming to a town near you. Let’s hope not. Peace.

    • Ziggy says:

      Demonic flooding 😵

    • Joshua Lake Oswego says:

      I’m going to go out on a limb and say that the main event will miss us to the north by 50 miles. It always does. The trend is already heading that way. The gradient for rainfall will be huge over relatively short distances.

      • Joshua Lake Oswego says:

        The 12z GFS puts us in the bullseye through Sunday afternoon. The NAM skunks us and puts Olympia in the bullseye. The GEM puts Longview in the bullseye with us still getting a good chunk. The Euro has consistently put us in the bullseye, but the 12z run won’t be out for a bit. I have seen these ARs go just north of us too often not to be pessimistic. Not that potential flooding is a good thing, but we could use some weather action and we can use much more rain.

  12. Ziggy says:

    Highs of 39 coming to Sofia early week. Going to be exciting 👍

  13. Roland Derksen says:

    Being a La Nina winter means it should be wetter than normal- as far as cold goes, it’s too early to say how it will go in January or February. My gut feeling is we will get a cold period sometime in mid or late January, but it won’t last long or be particularly intense.

  14. tim says:

    Excuse me i meant december 2014.

  15. tim says:

    Can’t complain about this december so far, remember december 2015 the warmest on record lots of 50’s and 60’s for highs here in seattle and all time monthly high of 66, bring out the ac.

  16. tim says:

    Indeed ziggy, a real 49/50 winter on the way just ignore tonight’s 00zgfs which has ridgeing buy christmas and beyond.

  17. Ziggy says:

    Looks like a super cold snap at months end for you in the PNW. Hopefully it holds on until I’m states bound mid January 🙏

  18. Andrew says:

    looking like NYC is gearing up for first major snowstorm in at least a couple winters. First NYC breaks its boring winter streak, next comes Portland! makes total scientific sense.

  19. Andrew says:

    It’s still very early in “snow season” but a bummer not to at least get some eye candy. As a snow lover, this is about the time I take a week break from models hoping my lack of attention will somehow spur some action (weather has a unique ability to make a full
    grown, reasonably rationale adult like me embrace any number of childish superstitions). Here is hoping the models do an abrupt pivot and give us some late month action. If not, lots of prime low-level snow window left, especially with what we know about La Niña patterns.

    • Ziggy says:

      Lol, I know that feeling. I do that with Facebook group, don’t log in for very days and boom hope for storm. This year has been not active yet.

  20. W7ENK says:

    I guess we’ll have to wait and see…

    • Ziggy says:

      What are you waiting for? It’s spelled out in his write up.

    • W7ENK says:

      Mark is a meteorologist, not a clairvoyant. He forecasts the weather, he doesn’t predict the future. “Wait and see” if the what the models are showing now — upon which Mark based his forecast — is accurate, how accurate, and where things go from there. Anything beyond 10 days is pure conjecture, speculation and wishcasting.

  21. ocpaul says:

    I really like ‘snowy mayhem’.

  22. Ziggy says:

    A lot of uncertainty it looks like. Must be rough a job to actually predict real weather??

    You do great job I think for Portland area. I remember you did snow from home with beer on deck lol.

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