Very Intriguing (Cold?) Weather Pattern Ahead!

November 25, 2013

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

ECMWF Weekly Charts

November 25, 2013

I’ll post again in a few minutes.  Here are the 4 weekly ECMWF upper level height anomaly maps from last night.  Pretty consistent theme!