Snow Coming To The Lowlands?

November 28, 2016

7pm Monday…

What a snowstorm in the Cascades!  The past 24 hours we’ve seen more than with any other storm so far this “winter”…

marksnow_mthood_totals

For the first time since 2011 we’ve seen a general opening of terrain at Timberline and Meadows ski areas in the month of November

marksnowpacknovember_skiareas

In one of two of these past few years we’ve seen warm rain obliterate part of the snow pack in November.  But this year I don’t see that.  This snow is here to stay; I see no period of warm rain in the next week or so.

That said, temperatures in the lowlands will be near or slightly above normal for the next 5-6 days.  Tuesday and Thursday look dry.

LOWLAND SNOW POSSIBILITIES

Is your favorite weather app showing snow or a snow/rain mix for next week?  Mine does…this is what it’s showing right now:

appcast

It says highs in the upper 30s next Tuesday and Wednesday with snow showers.  Even though that’s not in the range of our 7 day forecast, I figure I should address it if you’re seeing it right?

About 3 days ago some models (not all) were showing a big “arctic blast” coming up next week with a good possibility of snow in the lowlands.  For comparison, we have not seen arctic air move into Oregon since February 2014.  We’ve gone two winters without a deep freeze.  So of course that would be a big event.

But in the past 2 days models have backed off and (as of this evening) now show a typical “it might snow down to 1,000 ft” type event early-mid next week.

To summarize what we DO know

  1. The next 6 days will be very mild…some light rain at times
  2. A sharp drop in snow level comes Sunday or Sunday night, at that point snow may fall down into the foothills (1,500′).
  3. Next week will definitely be colder…it’s going to feel like December
  4. All areas should finally get a long overdue frost
  5. There is no sign of a big arctic blast for now

What we DON’T know yet since it’s still 7-9 days away

  1. If sticking snow will fall below 1,000’…it may or may not
  2. If it’s just a few days or a cold period that’s going to stick around for a week or more.

 

For the hardcore weather geeks…

The ensemble charts from both the 12z GFS and ECMWF sure don’t show a big arctic event like a few days ago (click for full view)

 

…but they clearly show a good agreement with 850mb temps dropping down into the -5 to -7 range next Tuesday/Wednesday.  That’s hilltop snow material (assuming there is moisture around) but tough to get snow down into the city at that temp unless we lose the mixing wind that is often present.  Some versions of some of the models (primarily ECMWF) have shown offshore flow and quite cold temps the latter half of next week, similar to what we saw around the New Year last winter.  That would be interesting because it could lead to some sort of overrunning moisture event following the cold.  Lots of possibilities ahead!

The surface temps (which in winter sometimes run too cold) from the 12z ECMWF ensembles show the cool spell next week, then warming beyond:

kpdx_2016112812_eps_min_max_15

The GEFS ensembles from the 18z run show that cold period next week as well with highs staying in the low-mid 40s (or colder if a day were to be cloudy/wet/white).

kpdx_2016112818_nxa_384

So stay tuned, as of now there’s no sign of a December 2009 freeze or December 2008 freeze & snowstorm.  But as I mentioned in last night’s posting…that can change quickly!

Chief Meteorologist Mark Nelsen