Late November Weather Slowdown In Pacific Northwest

7pm Tuesday…

The first half of November has been very warm in the Pacific Northwest, 3rd warmest on record (first half of month) at PDX.

Now that’s partially due to a long-lived atmospheric river event late last week through Monday. That was a real doozy in Washington, not as extreme in Oregon. Huge rain totals with record flooding the past few days in SW British Columbia and NW Washington. Portland picked up just under 3″ out of the event Thursday-Friday, an excellent forecast by forecast models.

Then a strong cold front finished things off yesterday with a gusty south wind that quickly switched to northwest in the afternoon. Peak gusts were in the 25-40 mph range for most of us, the 4th time PDX has seen a gust at/higher than 40 mph this season. Lots of moderate wind, but no windstorm in the valleys yet this season. Mental reminder: The HRRR model tends to over-forecast wind gusts, it’s been too high most of the time this season. Our GRAF model has done very well.

Rain is running well ahead of average for November…just over another 1/2″ will send PDX over the typical monthly allotment. But now the weather is slowing down dramatically.


WHAT’S AHEAD?

Much calmer weather which shouldn’t affect your day to day living…

Through at least Thanksgiving Day I don’t see:

  1. A storm of any sort west of the Cascades
  2. Lowland cold and/or snow
  3. A big snowfall to jump start the ski season

In general, upper-level heights will be a bit higher than normal along/off the West Coast. That has not been the case most of the time in the past month. This chart shows 500 millibar height (around 18,000′ overhead) averaged over the next ten days…the lines. Warm colors represent highs higher (warmer) than normal

That leads to less precipitation than normal…both the GFS and ECMWF ensembles are similar (GFS here). Not DRY, but DRIER THAN AVERAGE for this time of year.

Just beyond that time (later Thanksgiving Weekend and beyond) models diverge. At this point GFS ensemble members are bringing in a wet southwesterly flow again, but ECMWF & Canadian models think ridging moves overhead for drier than normal conditions through the end of November. We will see, that’s pretty far out. Regardless, I only see two rainy periods in the next week. That’s later Thursday through Friday, then again Monday (very light). These will be relatively weak systems, not significant wind producers. I love this chart…it shows all 51 ECMWF ensemble members for the next two weeks. Each square represents a forecast 6 hour maximum gust in Portland. The lowest part of the chart shows the average of all 51 members. With just a quick glance I can see where windy periods may show up, plus any real “outliers”. That refers to numbers much higher than others.

Gusty easterly wind tomorrow through Thursday morning shows up well on all ensemble members. Most interesting is that there isn’t a single ensemble member trying for a 50 mph gust in the next 16 days! Of course that doesn’t mean we don’t have a storm coming sometime beyond the next 7 days, but in general we don’t see a stormy period ahead.


SKI AREA OPENINGS

Last week things were looking up with 10-15″ fresh snow on the ground at the ski resorts. We were just a storm or two away from at least a few runs opening up on Mt. Hood. Then 5-6″ rain fell on that snow and warm/humid weather melted all of it! Cold showers last night dropped 2-5″ snow on those resorts. It appears only a dusting is on the ground down at Mt. Bachelor west of Bend. This is not unusual for mid-November as you see, but skiers/snowboarders just remember the big starts. 2017 and last year we had some nice snow on the ground at this point.

What’s ahead?

We sure don’t want to see those higher than normal upper-level heights over the next week as I mentioned earlier in the post. That means weak systems and a bit warmer than normal. So very little accumulation at the resorts at least through next Wednesday.

BUT, things can change quickly this time of year. Stay tuned to see if we get that cooler/wetter pattern as we go through Thanksgiving Weekend.

Chief Meteorologist Mark Nelsen

162 Responses to Late November Weather Slowdown In Pacific Northwest

  1. tim says:

    Maple valley weather on Twitter just released the euro.weeklies check it out , I don’t know how to post on here

  2. Ken in Wood Village says:

    Good evening ladies and gentlemen. I got off work around 3:30 today. Working 10 hour shifts this week is a pain…lol. I just woke up from a small nap. I probably will go back to bed around 8:30 because getting up at 3am comes way to fast.

    There are a couple of things I want to say in this post.

    First, I am loving how busy this blog has gotten since the “s” word has been talked about in the models…lol.

    Second, I wanted to mention about the system coming in. There is a good chance we could see thunderstorms tomorrow. I was looking at the HRRR and it shows small showers (but heavy) popping around the area. There is something I think is another reason why we could see thunderstorms but I want to mention it in my next sentence…lol.

    Lastly, (here is why I think about the chances of thunderstorms and snow) I am a little surprised no one has talked about the ocean temperatures and how they will influence the overall make-up of what we will be seeing coming out of the sky. Remember when Hank (I think it was you) posted the video of Pete Parson talking how it could influence the snow level? Where we normally could see a 1,500-foot snow level but with the current colder ocean temperatures we could see it down to sea level instead. I really don’t think the models are taking the lower ocean temperatures into its forecast modeling. We are really in uncharted territory just because of the lower temps in the ocean.

    With that being said, we all will be watching how the models will be doing the next few days.

    W7ENK said, “hanging out there at or beyond Day 10 before it finally evaporates.” (I corrected our to out!!) I’ve seen it evaporate too but then show back up 5 to 7 days out.

    I think I’ll end it there. I may watch the 00Z GFS come in before I head to bed. I may or may not post something if I see anything interesting…lol. Have a good night, everyone 🙂

  3. K700 says:

    Crossing my fingers for December snow, a repeat of December 2016 would be amazing. I think it’s been 4 winters since we’ve had any aside from maybe some flakes in the air or conversational snow.

  4. Andrew says:

    while I definitely see hints of snow in ensembles around December 6-7, nothing screams imminent snow threat to me. But keep in mind, we didn’t even have even this level of (admittedly low end) eye candy until January last winter so reasons to be encouraged for sure. The very cold air starting to pool up in lower british columbia in early December is a key ingredient and always presents potential for action. Already feeling like this December has more promise than past few.

    • Oh yeah! I forgot, last year it took awhile for snow to be on the models, of course it would happen on the last 2 days of the run sometimes, but nothing as consistent snow.

      I’m just hoping we get somewhere between 2-12 inches of snow, because at 2 inches, it’s enough for sledding, but anything above 12 inches could cause some problems.

      But definitely no big snowstorms until mid December. Just maybe an inch or 2, but that’s still a “if”.

  5. Anonymous says:

    The dilemma is: am I going to get more upset if we don’t see any hints of snow in the models at all or when there’s snow in the models and it never materializes 🤔

  6. W7ENK says:

    End of run, end of run, end of run…

    Always at the end of the run.

    Please folks, don’t get too upset when this thing keeps pushing out, day by day, always hanging our there at or beyond Day 10 before it finally evaporates. This happens every year, it’s why we call it “La-la Land.”

    • We won’t get upset. But so far, it’s not getting pushed out.

      I know not to get too excited, because I don’t even benefit from dry and cold air.

      Also I wouldn’t say it happens every year, I don’t remember something like that happening at all in recent years. But I could be wrong.

  7. Ned Bergundy says:

    I have access to a trove of private (not for public use) weather modeling. There are things that the Euro and GFS aren’t picking up on. Check back with me in a few days about what promises to be a very enticing set-up for the coming weeks.

  8. And another interesting Gfs run, some snow, and the same very cold air moving in at the end of the run!

    • tim says:

      Yeah looks likes highs in the mid and uppers 30s if it verifies here in seattle anyways definitely very early in the season for this kind of cold, just look what’s happening in Alaska right now.

      • tim says:

        The cfs is showing below norm temps mid december but that could only mean mt snow and cool valley rain or maybe something els.

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