Very Intriguing (Cold?) Weather Pattern Ahead!

This weekend was just about the best November weekend I can remember.  For a gardener it was incredible, totally dry (drier than any spring day) vegetation so I cleaned up big-time.  Plus I put up my Christmas lights now instead of waiting for yucky and cold wet weather.  No one can see my lights, so I turned them on; otherwise that would be socially unacceptable!

The weather stays real quiet through at least Friday, maybe a bit beyond.  As a result, no Thanksgiving travel issues anywhere in the Pacific Northwest…probably through Sunday.  November will end much drier than normal.  Lucky for the ski areas, the bright blue skies allow the snowpack to stay consolidated even with 50 degree temps the past two days.  Meadows had a preview weekend and Timberline is just barely operating.  Skibowl will be opening their tubing hill this coming weekend since they’ve been making snow.

So we’ll just jump ahead to the good stuff…

Models are advertising a big change to our weather pattern about next Monday or just beyond.   This is just beyond our 7 Day forecast, thus little or no reference on TV…for now.  But that’s what social media (like this blog) is for.

There is a strong signal from all models that upper level ridging will build north from the eastern Pacific into Alaska, pushing upper level disturbances from British Columbia, the Yukon, or even the Arctic Ocean south into the mid-latitudes (where we live).  This can be a classic setup for an arctic blast here in the Pacific Northwest.  Take a look at the 500mb height anomaly for next Tuesday on the 18z GFS and 12z ECMWF:



Pretty decent agreement…look at the actual map from the ECMWF for Wednesday afternoon!  Remember this is 9 DAYS FROM NOW.


That’s definitely big cold spell material, and the GFS is similar.  Of course the devil will be in the details.  The ECMWF has us cold enough for snow down to 1,000′ or a little below Monday, then just cold and dry.  It also had a 2nd system moving down the coast for a possible dose of snow (what you see here) later Wednesday and Thursday with a very cold/strong Gorge wind.  Due to it’s better performance in general, I’m giving it more weight than other models the next few days.

Here are the two ensemble charts from the 18z GFS and 12z ECMWF:



Note large variations in the ensembles after Saturday.  Extremely chaotic.   As a result, we could skate through this with a marginal snow shower setup, or have the best arctic blast since 1998…who knows right now.  OR, in the next two days the ridging could decide to develop closer to us again.  Remember that two weeks ago it only took about 3 days for models to go from “coldest weekend so far” to slightly warmer than average in the end.

I can almost guarantee models will be all over the place for another day or two.  That, plus the fact that it’s just beyond our 7 day forecast anyway, means I won’t be making a big deal out of this on-air…yet.  There has been some serious meteorological eye-candy though the past two days!  And there will be more to come…enjoy.

Chief Meteorologist Mark Nelsen

144 Responses to Very Intriguing (Cold?) Weather Pattern Ahead!

  1. WEATHERDAN says:

    This is just a reminiscence not a forecast ok. In very late November 1972,decades before the internet and the channel 12 Weather Blog I was a weather junkie. I was a college freshman that fall. Anyway in very late November on a Friday night a very young Chuck Wiese was doing the 6:00 PM weather for KOIN tv. He was filling in for Ferris Top that night. So young Mr. Wiese (about 18 at that point) said we were going to see some cold air move in next week. He predicted some snow flurries on the next Monday and a high of 39. Little did we know what a cold airmass was lurking just to the North. On Sunday which I believe was December 1 we started getting some flurries that late afternoon. Late that night the skies cleared and temps dropped to the upper teens. Monday was bright and sunny with a high of just 33. The next day on Tuesday the snow started around 10:00 AM in Salem. By the time it stopped on late Wednesday we had nearly a foot of snow on the ground. Then it cleared out and we had several nights with lows as cold as -12 in Salem. The cold and snow lasted two weeks. In fact it was cold from about December 2nd until December 21st. I only mention this because the current situation reminds me a lot of that late November. Now you hear the forecasters saying gonna get cold next week but maybe only a little moisture left to snow with. I hear predictions bolder than others about what might happen but personally I just have a gut feeling that this time we may get to see some sticking snow Monday or Tuesday. Also it looks the cold air might stick around when the next batch of moisture arrives the following weekend. But this is just the kind of Winter predicted by Pete Parsons., lots of extremes. I hope you all have a great Thanksgiving, Peace.

  2. W7ENK says:

    Uh oh… EURO is having a moment…

  3. Rob - Southeast Portland says:

    12z GFS has latched onto the EURO/GEM in the mid-term with the handling of the energy over Alaska and trough down over us and that it too has sped up in timing as the other model camps have been showing within a 5-6 day window. Important to note the 500mb pattern upstream setups now after day 3-4. Initial shot of arctic air arrives Sunday. It wasn’t a brutally cold run, but plenty cold enough and with bitter east wind. In fact, Monday-Tuesday looks like a damaging east wind storm/downslope for PDX/VUO metro as the arctic front heads south.

    My only real concern was this run not amplifying the Block as far north up through Alaska/Yukon and tilted a bit further east, but it’s not a great concern by any means. Beyond 6 days I prefer and lean on the EURO much more throughout the 6-10 day window. Maybe a blend of the EURO/GEM.

  4. Marcustheweathernut says:

    What’s up….. Nice time for tower temps to be out of commission????

  5. Marcustheweathernut says:

    12z gfs = wow!!!! Cold, snow cold snow for an exsteded period!!!:)

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