2017: First Week Looks Cold

December 26, 2016

9:30pm Monday…

The astute FOX12 viewer will notice a sudden drop in the high temperature Monday…the 2nd of January.   And your weather app is looking quite chilly for next week too isn’t it?   Well it’s looking like we’re going to turn quite cold next week once again.

Models all show a similar pattern developing Sunday through sometime later next week…an upper-level ridge builds over Alaska.

500vty_f156_bg_na

That forces a cold airmass to dive down through western Canada and into the Pacific Northwest late Sunday through next week.  In general, the pattern is the same on all models.  As a result I’m quite confident we’re headed for a very cool first week of January 2017!

But will it just be cool like earlier this month?  Or could it be a real arctic blast, one we haven’t seen in 3 years (since December 2013).  That’s a good question and I don’t have an answer for you yet.

For reference, I’d consider a widespread Pacific Northwest arctic blast one in which 850mb temps drop down to at least -12 (celsius) over Portland/Salem.  The last 5 times that has happened?

December 2013:  -14
November 2010:  -12
December 2009:  -12
December 1998:  -18
December 1990:  -22 (coldest 850mb temp on Salem sounding record)

You can see a true widespread Pacific Northwest outbreak of deep arctic air is quite rare.  It’s like the weather geeks (including me) are reaching for that “big one” each winter, but most winters will end in disappointment.

It could possibly happen next week.  The ECMWF model run from this morning was that cold, but other members of its ensembles were not.  Same thing with the GFS model.   Check out the ECMWF ensemble chart from this morning:

ecmwf_ensemble850

Quite a variety of solutions by next Tuesday/Wednesday, but in general it looks cool. Check out the ensemble forecast temps from the same morning run:

ecmwf_ensembletemps

A pretty clear signal for a chilly week ahead…starting Monday.  It was interesting to note that only about 1/2 of those ensemble members showed 2″ or more snow over Portland in the next 8 days, but that number jumped to 46 of 51 members by the 12th day.  The point is that once real cold weather arrives, moisture will likely interact with it at some point.  Especially since the pattern seems to stay cold for a while.  Look at the 1st and 2nd week of last night’s ECMWF monthly run.

500za_week1_bg_na

 

500za_week2_bg_na

That’s a cold pattern with the upper-high remaining over Alaska and downstream troughing over us.

This evening’s GFS run is not nearly as cold as the ECMWF for next week; it looks more like what we saw earlier in December.  But I’m sure there will be lots of twists and turns the next few days on the models.

Stay tuned..

Chief Meteorologist Mark Nelsen


Major Snow Storm In Cascades Begins Soon

December 26, 2016

4pm Monday…

I hope you all had a Merry Christmas!  Time to get updated on the latest weather happenings.  I see I didn’t miss much here…I was in Florida Monday AM through Saturday afternoon.  The morning my family and I flew out (Monday) it was COLD sitting in the economy lot with ice pellets/snow/rain pelting us along with a breeze.  But the south wind arrived as expected and the vast majority of the metro area made a quick switch to rain.

Today we’ve got a front moving onshore with lots of precipitation.  Due to strong westerly wind up around 5,000′ following the front later tonight through Tuesday, we’ll get maximum snow enhancement along the Cascades, and Blue Mountains in NE Oregon too.

This storm is going to be a major snow storm up in the Cascades:

rpm_snowaccum

What timing too…1.5 to 2+ feet of snow in the Cascades right during the peak of the ski season.  I’ve heard in the past that these two weeks of Christmas Break are HUGE for ski areas, accounting for a large part of their winter income.  So the good times with Ski Season 2015-16 will continue!

Also note the heavy snow for the Blues and Wallowas, mainly during the daytime Tuesday:

rpm_snowaccum3

Eastern Oregon has been extremely cold this December.  In fact as of today it’s the 2nd coldest December on record in the Baker Valley (Baker City/Haines/North Powder).

marktemp_last12days_bakercity_lows

The presence of snow cover allows any clear night to turn frigid.  Plus we’ve seen a real absence of moist/warm southwesterly flow to clear out the trapped low-level cold air in the Intermountain Region.  The average low at Baker City is 15 this time of year, so getting below zero IS quite cold.  This is a December to remember over there!

The cold air will stay entrenched the next 48 hours, and that means the strong south & southeast wind through the Blue Mountains will be here with this snowy system too.  The result?  Blowing and drifting snow with near-blizzard conditions again along parts of I-84 Tuesday from Emigrant Hill to Baker City.  There won’t be all that much snow in the valleys, but lots of blowing/drifting.

The storm leaves the area by Wednesday sunrise so Wednesday and Thursday look pretty tranquil across the Pacific Northwest.  A weak system will drop in over us Friday, lowering snow levels down below 2,000′ again.  There won’t be much moisture with that one though…just a few more inches in the Cascades.

What lies beyond for the first few days of 2017 sure looks interesting…more on that in a post later…

By the way, you are living through the coldest December (or any month) in 3 years here in Portland.  The average temperatures of 37.2 degrees is just slight warmer than the cold December 2013 and 2009.  Things have FINALLY gone back to normal (at least for now) after a long almost 3 year period of very warm weather.  We’ll see how long it sticks around.

One more quirky fact…December is the only winter month that has been getting COLDER over the years here in Portland.  January/February/March have definitely been going up, but December for some reason is going DOWN.  Strange eh?

december_portlandtemps

Chief Meteorologist Mark Nelsen