November Ends Mild & Wet, but Dry & Cold December Weather Ahead

1pm Thursday…

November has been a very cold month across much of the USA, but not west of the Rockies!  We are running a few notches above average in the Pacific Northwest.  

As you can probably guess, it’s been quite dry this month too; Portland has only seen 2.44″ rain so far, less than 1/2 of average.  We’ll see maybe 1/2″ rain at most Friday so November 2018 will go down in the record books as “warmer & drier than normal”

The reason is that we continue to see a weak/splitting jet stream or occasional upper-level ridging overhead.  This has been the case since at least early October.  Let’s go forward through the next week and you’ll see what I mean.  

Here’s the 300mb (around 30,000′ up) chart for today.  A classic “El Nino Winter” split flow.  A “bowling ball low” is sliding by to our south leaving us dry.

Northern/central California is getting a soaking.  All sorts of watches/warnings/advisories down there:

Tomorrow a weak system approaches from the west and moves directly over us Saturday.  This drops snow levels below the passes and brings cold showers to the lowlands of Western OR/WA the next two days.

Note the strongest windspeed is well to our south, so we don’t get a massive soaking or any stormy weather; just cold showers plus maybe 6-10″ snow in the Cascades.  By Monday an upper-level ridge is developing again…while another one of those “bowling balls” is getting ready to slide by to the south.

By Wednesday, California gets another wet (white in mountains) system, possibly aimed more for the southern part of the state.  Over us the upper-level ridging is holding strong, but centered well offshore.


This pattern screams UNUSUALLY DRY START TO DECEMBER IN THE PACIFIC NORTHWEST.  Thus the bold lettering!  The ECMWF has no precipitation over our region from Sunday night through next Friday night

But what happens down near sea level is likely what you’re really going to notice.  Behind that cool system coming in Saturday, a surge of cold/dry Canadian air drops south.  The ECMWF temperature departure (from normal) for next Tuesday through Tuesday the 11th shows very chilly weather across the interior West as surface high pressure traps the cold air in place.  The sun is too weak in December to heat up the cold valley/basin air east of the Cascades.  Inversion season…

The result is this surface map for Monday; cold high pressure has settled in for an extended stay east of the Cascades.  Chilly east wind is already blowing in the Gorge by that time…brrr!

By Wednesday it’s firmly entrenched.  Huge east wind through the Gorge; winter-strength gusts with highs only in the 30s (icy waterfalls?).  Temps peak only around 40 or so east metro and mid 40s for the rest of us.  That dry air will keep us clear so calm areas drop into the upper teens next week  (Battle Ground, Hillsboro, Scappoose).  It isn’t an arctic freeze coming, but you should have your irrigation systems drained by now anyway.

To summarize:

  1. Two days of showers ahead, possibly a few leftover Sunday
  2. 6-10″ snow will fall at ski resorts, but then it’s possible no new snow after that until at least NEXT weekend.
  3. Next week should be all or mainly dry
  4. This is the last of the warm 50+ degree weather, next week will be sharply colder and just plain frigid in the usual east wind areas
  5. That wind begins Sunday night
  6. IF MOISTURE RETURNS FROM THE SOUTH AT SOME POINT LATER NEXT WEEK? Cold air would assure freezing rain or snow in the Gorge and Eastern Oregon.  Of course a “perfect” lineup of moisture plus cold air could bring that threat into at least the eastern metro area.  I’ll be watching that VERY closely.
  7. There is no sign of a typical stormy weather pattern ahead; it’s possible we have begun a “drier & milder than normal” El Nino season.

Chief Meteorologist Mark Nelsen

32 Responses to November Ends Mild & Wet, but Dry & Cold December Weather Ahead

  1. kitchen says:

    Pretty! This has been an extremely wonderful post. Thank you for supplying this information.

  2. W7ENK says:

    Hard frost, and standing water had a skin of ice this morning.

    The Moon and Venus together made quite a spectacular pair!


    (not my photo)

  3. Anonymous says:

    Hard frost, and standing water had a skin of ice this morning at my place.

    The Moon and Venus together made quite the spectacular pair!

  4. Andrew Bartholomew says:

    Hey – I recently purchased an Ambient Weather Station for my home and was looking for some guidance on placement. My preference would be to attach the mounting pole to my back fence free of any tree or building cover. The station would sit about 7-8 feet about the ground surface and about 15-20 feet from the back of my home. Will that be sufficient for getting accurate measurements? I don’t have a large property and would prefer not to use my roof, which is quite steep and would require some additional installation help. I appreciate any feedback or ideas. Thanks

  5. K says:

    Hate to say it, but this is actually looking even worse than last year. At least we had extremely strong E. Wind last year. This week even the E. Wind looks to be only decently strong, with not much interesting weather even down the line where a strong storm or snow event usually is shown.

  6. K says:

    Models aren’t looking too good right now, very reminiscent of last year. Color me surprised if we get something good in December.

  7. Mike says:

    Eugene has had the driest May-Nov period on record (since 1890), and the 12 month period ending 30 Nov was the 11th driest. As a relative newcomer here, I’m curious about “dry and warm winters” with El Niño. Five out of the last six winters have been unimpressive with snowpack. If El Niño is associated with dry winters, and last year’s La Niña gave us half normal rain (Dec-Feb), what produces “normal” winters? December 4 marks one year since the drought began, with the huge stuck ridge over Eastpac last year. So many people have told me “it didn’t used to be like this.”

    • Anonymous says:

      Born in the NW in the fifties..
      Continuously wet and dreary winters were the norm when I grew up (Portland and Corvallis). Usually snowed once or twice in the winter but still,for the most part not all that much.
      Summers started in July and ended in September and they were hot and dry back but I would summer is longer and winter isn’t as long or as cold but just a dreary.The 60s and most of the 70s had big mountain snow packs except the winter of 76-78 which was a dud and maybe the start of the current trend..?
      My thought about all this is that things are warmer and drier overall, but is this is a long term trend since the end of the last ice age? Or just a multi-decade trend that could switch back at any time. Who knows for sure.
      Currently the Arctic is going through BIG changes that cannot be overlooked. But it has been warming for thousands of years. Carbon concentrations are getting very high and must be a contributor.
      Fires? Fire suppression has something to do with that problem.
      Drought? Who knows and it’s happened before (ie. the 30s).
      Snow? Yeah we seem to be getting less and at higher elevation.
      But that being said, we’ve never been using so much technology and resources to document the climate as we are today.
      Bottom line…it was wetter and cooler. And more depressing!

  8. 4.93″ for November here. Not as anomalously dry as Portland, but many of the storms that gave Roland a real soaking barely nicked me.

    • Roland Derksen says:

      Clear skies here today. It feels like we’re back to a sunny pattern just like earlier in November- but noticeably cooler

  9. We will be filling our propane tanks come Monday.
    We have learned that using propane heater is more cost effective than using electric heaters.

    We have CALCULATED what we need.

    Here in my area, Castle Rock, Wa.
    We are alreading beginning to freeze.

    Now all you little thermometers stuck who knows were are never correct for this area.

    I just wish they would fix them..or…get a unit installed in this area because i swear they got those sensors stuck in some warm shed some where…heck…send a weather person with a Slingometer or portable wewther station of some kind to set up in town..like at Select Grocery outlet.

    Any who. It will be interesting to see this so called more power myth on cold days. With solar.

    • alohabb says:

      Look at a Mitsubishi ductless unit, or whole home air handler. It would be even cheaper to run than the propane, and unlike other heat pumps, it can give you 100% of the rated unit heat at 15 degrees.

    • When it comes to overnight lows, local microclimates can matter a lot. Looks like you’re in a cool one.

  10. runrain says:

    An east wind storm next week could be kind of inty.

  11. Roland Derksen says:

    I’m ready for some sunshine. It been kind of drippy here lately.

  12. alohabb says:

    Large earthquake in anchorage. Our office is working on assessing the damage.

  13. Wouldn’t be surprised if some areas in the lowlands see flakes on Sunday morning up this way. Could well be cold enough for snow nearly to sea level, and there’s a chance of some lingering showers still hanging around. But just a chance, and flurries at best, no accumulation.

    After that, looks dry. What with the chilly start to the dry spell, it could be a set-up for a prolonged cold, foggy, frosty inversion. Forecasts are not currently calling for one, but such things can be hard to forecast (and once they set up, can be quite persistent). Time will tell.

    For those of you in Portland, east winds look like a good bet. Again, hard to tell just how cold or how windy, all depends on how profound a cold pool there is in the Columbia Basin. And again, it’s often hard to forecast how just strong such inversions will get.

  14. We had Snain Earlier this morning…and temps fluctuating between 43 and 41.

    and now I see Pastel Blue Sky whitish- grey -blueish clouds.

    Rain barrel was 3/4 empty, now its spitting water out the over flow…

    I hope it don’t freeze here tonight as that will be a mess.

  15. Jason Hougak says:

    The Sierras are getting hammered.

  16. Jason Hougak says:

    Mild November… wild January

  17. pappoose in scappoose says:

    To bad one of those “bowling balls” isn’t dropping down from the Great White North!

  18. Paul D says:

    Same old abnormal weather = the new normal 😦

  19. K says:

    Well, this is reminding me a lot of last winter….. 😦

  20. W7ENK says:

    Dry.

    Always with the dry…

    Too dry!!

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