snow

8pm Sunday…

Here we are, finally at the end of Christmas Vacation for the kids.  It’s been a fun two weeks for many of us; full of family events, parties, and WAY too much eating and…drinks.  Time to get back to work and school.  First, a quick recap of where we stand meteorologically:

  • We are at the midpoint of our  “cold season/winter/storm season” (whatever you want to call it) west of the Cascades.  That’s November through February.  By March 1st we’re done with winter west of the Cascades unless we get a sloppy/wet brief snowfall.  Last year’s early March record cold & snow would be an extreme example of how winter can hang on very late here every few decades.
  • It’s been so boring for meteorologists with a lack of stormy weather, lowland snow/ice, etc… But great for you!  Weather has barely affected our lives so far, except for the brief snowy travel issues at Thanksgiving and lack of snow in Cascades.  Officially we have not seen measurable snow in Portland.

Now we seem to be turning a corner, at least for the next 10 days.  We’re now in a cooler & wetter weather pattern; back to normal!

Highlights

  1. Expect at least SOME rain each of the next 7 days as a series of relatively weak weather systems move off the Pacific and into the Northwest.
  2. None of these systems look particularly strong, windy, or cold.  But each will add to our January rain total in the lowlands and snowpack in the Cascades
  3. Snow levels vary between 1,500′ & 5,000′ through Saturday
  4. Models are hinting that snow could stick even lower at some point between next Sunday and the days following (12th-15th).  Some produce NO snow, others give us a big outbreak of cold arctic air and several inches.
  5. That period will likely feature the lowest snow levels since our brush with lowland snow Thanksgiving weekend.  I’ve put on my snow tires (finally) just in case…

Expect 2 to 5 feet of snow in the Cascades now through next Sunday. Here’s the ECMWF model (Euro).  Can’t wait to see that 25% of normal snowfall on Mt. Hood jump up big-time the next 10 days!

ECMWF Snow Accumulation

What I don’t see within the next week (through Sunday the 12th)

  • Sticking snow at lowest elevations west of the Cascades OR along I-84 in the Gorge
  • Freezing Rain
  • Flooding
  • A Windstorm
  • A Hard Freeze (below 28 degrees west of Cascades)

We’re in a wet westerly flow right now with a nice Pacific jet stream aimed at the West Coast.  Here’s the ECMWF ensemble forecast 500 millibar height map right now:

euro now

But by next Monday, ALL models agree we’re in a pattern with an upper-level high out around 150-160W longitude (south of Alaska) and a cold trough centered over the western USA.  This is the ECMWF for next Monday

euro ensemble monday 14th

The Canadian and GFS are similar.  Click on each for a larger view.

So that’s relatively simple…cooler (or colder) and still a bit wet 8 days from now.  But in our climate, with hundreds of miles of 50 degree water just to our west, everything has to work just right to get us real cold or snow all the way down to sea level.  So all models may agree on the general pattern by next Monday, but how we get to that point and exactly how all the weather features line up is critical.  Slight changes mean the difference between a hellish snowy commute at some point in Portland, or just 40 degree rainy weather.

Example A:  For several days the (new and improved) GFS model has been constantly trying to dig weather systems farther west out of Canada as they move southeast into the cool trough across the western USA.  That’s for this coming Saturday, Sunday, or Monday.  It has been most aggressive bringing cold arctic air south into the Pacific Northwest.  Today’s 18z model was very extreme, going all out for widespread snow in our area with a cold east wind Sunday night.  See the arctic boundary (snow to sea level) way down into Oregon on that model (yellow highlighting)

gfs18zSunday evening

The GEM at the same time has a surface low sliding into NW Washington, keeping cold air bottled up north.  On Sunday evening the GEM would say it’s 40 degrees with a gusty south wind blowing in Portland…totally different even though upper-level is similar.  It’s all about low/high pressure locations for us.

gem12zSunday evening

The ECMWF?  It says “mainly dry” with the arctic boundary up north and a weaker low heading farther south.  This says snow showers to 1,500′ and nothing interesting happening in Portland Sunday evening.

ecm12zSunday evening

To summarize:

  1. I think SOMETHING interesting is on the way NEXT week, but it’s too early to know what.  Too early to know if it involves lowland snow/ice/cold or just a brush with flurries again like Thanksgiving.
  2. Keep a close eye on forecasts, this blog, and on-air at FOX12 OREGON.
  3. As a nod to the GFS, I put one little lonely snowflake mixed in with the rain on our 7 Day Forecast (next Sunday)
  4. And, for the love of any sort of deity…stop staring at weather apps!  They are good for general weather forecasting during benign weather, but useless in situations like this.  Totally automated.  Plus, what does a snowflake for next Monday mean; a snowy day? a few flurries?

Weather App Snow Forecasts

Chief Meteorologist Mark Nelsen

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