December 2016 Observations and Model Discussion for the Pacific Northwest

[Front Ranger]

Yep pretty chilly though

 

For sure. And pretty close to something really good days 9-10.

[Phil]

Y'all should be drooling over the 12z GEFS. Perfect EAMT/NAMT synchronicity w/ the tropical forcing/poleward WAFs. That's how you build an AK/Arctic block and downstream SE ridge.

Also, via this particular conduit, you guys wouldn't even need stratospheric help to maintain the proper waveguide. Perfect way to prevent a tropospheric coupling with the PV so long as the tropical/extratropical forcing connection holds.

[Front Ranger]

Y'all should be drooling over the 12z GEFS. Perfect EAMT/NAMT synchronicity w/ the tropical forcing/poleward WAFs. That's how you build an AK/Arctic block and downstream SE ridge.

 

I'm just loving the blocking we're seeing this season so far, with no sign of it going away any time soon.

[Brennan]

Y'all should be drooling over the 12z GEFS. Perfect EAMT/NAMT synchronicity w/ the tropical forcing/poleward WAFs. That's how you build an AK/Arctic block and downstream SE ridge.

We need some consistency. Two days ago long range ensembles looked nothing like this.

 

The CFS believe it or not DID show this setup coming around mid month about a week ago...

[Phil]

I'm just loving the blocking we're seeing this season so far, with no sign of it going away any time soon.

Same. That recent MJO passage appears to have rejiggered the background wavetrain just enough (broadened Walker Cell and slightly retracted Pacific Hadley Cell) to allow the more classic Niña mode of +QBO/off-equator WPAC forcing to take hold and build the NPAC anticyclone poleward.

 

Ironically, the fact the Niña background was so weak earlier was probably a benefit..otherwise it might have resisted the intraseasonal/MJO forcing that altered it in your favor. Amazing how complicated and unpredictable this stuff can be.

[Perturbed Member]

1 1/3 km WRF shows 2-4 inch totals for tomorrow morning across the PDX metro. 

 

Soundings right before precip arrives indicate about 34-35F at the surface:

 

http://www.atmos.washington.edu/mm5rt/data/current_gfs/images_d4/kpdx.24.0000.snd.gif

 

 

By 7 AM, airmass is saturated and surface is 32-33F with about 2 inches of snow on the ground and a bit more snow to fall:

http://www.atmos.washington.edu/mm5rt/data/current_gfs/images_d4/kpdx.27.0000.snd.gif

 

 

In reality it will probably be just a bit too warm for this to happen. 

[TT-SEA]

Some clearing skies out here now...

 

[MossMan]

Lots of sun and 39 degrees currently with a stiff northerly breeze...time to get the Christmas tree!

[BLI snowman]

1 1/3 km WRF shows 2-4 inch totals for tomorrow morning across the PDX metro.

 

Soundings right before precip arrives indicate about 34-35F at the surface:

 

http://www.atmos.washington.edu/mm5rt/data/current_gfs/images_d4/kpdx.24.0000.snd.gif

 

 

By 7 AM, airmass is saturated and surface is 32-33F with about 2 inches of snow on the ground and a bit more snow to fall:

http://www.atmos.washington.edu/mm5rt/data/current_gfs/images_d4/kpdx.27.0000.snd.gif

 

 

In reality it will probably be just a bit too warm for this to happen.

Timing and precip rates look good, though. I like the idea of a general 1-2" above 200' in that 6am to 10am period. I don't think anything will stick at sea level.

[kokaneekidz]

Just got our first dusting in Mukilteo in the last half hour. Now please please please setup a strong convergence zone all the way thru tuesday

[bainbridgekid]

Hail covered roads currently at the Clinton ferry dock on Whidbey Island. Nice little CZ up there.

 

 

My friend who lives up there also sent a picture of her yard covered in hail.

[Perturbed Member]

Timing and precip rates look good, though. I like the idea of a general 1-2" above 200' in that 6am to 10am period. I don't think anything will stick at sea level.

 

 

1-2 inches @ 200' and above would cover most of the metro and would probably make most weather nerds here happy. Probably trace at best for downtown/airport. 

[Perturbed Member]

http://www.atmos.washington.edu/wrfrt/data/2016120412/images_d4/msnow24.36.0000.gif

[TT-SEA]

Base at the Summit at Snoqualmie got 19 inches of snow over night.

 

Now at 30 inches at the base and at least 60 inches on top (although that number has not been updated for awhile).   

 

They are assessing the situation this morning and it sounds like they will be opening soon.

[SilverFallsAndrew]

Everett reporting light snow and 36 now.

[luvssnow_spokane]

Pretty fun morning ... Dropped rapidly down to 34.2 this morning with pretty heavy ice pellet shower. It was fun to see my temp go from 39 to 34 in less than an hour. Warmed back up now (which was expected) but having this and knowing it can only get better is awesome!   

[Kayla]

Timing and precip rates look good, though. I like the idea of a general 1-2" above 200' in that 6am to 10am period. I don't think anything will stick at sea level.

 

Agreed. Can't really keep ignoring the WRF and soundings at this point. I'm thinking the NWS will be tweaking things this afternoon showing accumulations down to ~200'.

 

Timing is great for accumulations, not so great for commuters tomorrow morning, especially over Sylvan Hill/Burnside etc.

[Kayla]

http://www.atmos.washington.edu/wrfrt/data/2016120412/images_d4/msnow24.36.0000.gif

 

Shows 5-8" of snowfall for me over the next 24 hours, I'll take it!

[Heavy Snow]

Also, via this particular conduit, you guys wouldn't even need stratospheric help to maintain the proper waveguide. Perfect way to prevent a tropospheric coupling with the PV so long as the tropical/extratropical forcing connection holds.

 

I just took a look at updated run of all the 12z GFS ensembles at Day 12 and Day 15 and lots of members have an Arctic Blast for the PNW on either on those days. 11/20 members or 55% show an Arctic Blast at one point in their run. I've never seen this many ensembles this bullish on Arctic air ever n the long range. I have a feeling your forecast of a possible Arctic Blast for us mid/late December will be right. 

 

http://i.imgur.com/3kSu39V.gifhttp://i.imgur.com/OsnTibz.gif

[luvssnow_spokane]

Shows 5-8" of snowfall for me over the next 24 hours, I'll take it!

I am still a little bummed it  STILL shows a trace to nothing for my location here in the swamp... I had hoped it would have improved but been pretty consistent. 

[TT-SEA]

Gorgeous at Snoqualmie Pass now...

 

[Gradient Keeper]

Ah crap!

 

An error occurred

You have reached your quota of positive votes for the day

[luvssnow_spokane]

 

Ah crap!

 

An error occurred

You have reached your quota of positive votes for the day

 

Don't you hate that!!!    <_>

[Front Ranger]

HRRR likes some accumulation in the N Interior and Vancouver BC area tonight.

 

[FroYoBro]

HRRR likes some accumulation in the N Interior and Vancouver BC area tonight.

 

hrrr.gif

 

It is almost time to start watching the HRRR radar loops for tomorrow morning in the Portland area. I always like following the HRRR for moisture when events are close. 

[Weather101]

HRRR likes some accumulation in the N Interior and Vancouver BC area tonight.

 

hrrr.gif

Hopefully

[Front Ranger]

I am still a little bummed it  STILL shows a trace to nothing for my location here in the swamp... I had hoped it would have improved but been pretty consistent. 

 

You're at 560'...you should do fine over the next couple days.

[TT-SEA]

It is almost time to start watching the HRRR radar loops for tomorrow morning in the Portland area. I always like following the HRRR for moisture when events are close. 

 

 

Its already time.. some updates run the loop out through tomorrow night.  

 

Here is one that did go all the way out.

 

http://rapidrefresh.noaa.gov/HRRR/jsloopLocalDiskDateDomainZipTZA.cgi?dsKeys=hrrr_jet:&runTime=2016120415&plotName=1ref_t1sfc&fcstInc=60&numFcsts=37&model=hrrr&ptitle=HRRR%20Model%20Fields%20-%20Experimental&maxFcstLen=36&fcstStrLen=-1&resizePlot=1&domain=t1

[Gradient Keeper]

 

Mark Nelsen?[/quote

 

No way. It's Rob or Jesse.

Well, considering I am Rob........ Who are you by the way???

[Front Ranger]

18z NAM is looking quite juicy with precip tonight and tomorrow morning.

[kokaneekidz]

Radar shoving the pscz towards Arlington now!!

[Trainwreck]

Well, considering I am Rob........ Who are you by the way???

This High Desert Mat from Marks blog. Over in Redmond Or

[TT-SEA]

Absolutely dumping snow and sleet here again.    Secondary c-zone just fired up in the last 20 minutes right over my area.

[Gradient Keeper]

This High Desert Mat from Marks blog. Over in Redmond Or

Ahhh, alrighty. You should be real white coming up. Big winter ahead.

[luvssnow_spokane]

Absolutely dumping snow and sleet here again.    Secondary c-zone just fired up in the last 20 minutes right over my area.

Yeah I am literally watching the UW radar and saw it fire up rather rapidly. nice! Enjoy!

[seattleweatherguy]

Any chance c zone gets over bothell or mountlake terrence

[VancouverIslandSouth]

The WRF is currently showing more snow over Victoria in the next 48 hours than there has been in the past 4 years. That said the snowfall totals it's shown over the Island have been pretty inconsistent. It hasn't made up its mind on whether things are going to stall and dump over East Vancouver Island, or slide south and given widespread totals of 2"+. I've learned to be skeptical of the totals this model shows, often it underdoes it in the initial snow for full on Arctic blasts and overdoes it in more marginal/overrunning situations. This time it's a tough call because this is setting up to be more of a hybrid, not quite a traditional Artic blast but much colder than the more typical marginal events where the WRF shows large accumulations with 925mb temps never falling below -2C.

 

http://www.atmos.washington.edu/wrfrt/data/2016120412/images_d4/wa_snow48.48.0000.gif

[Front Ranger]

Pretty much all models picking up on significant CZ possibilities over the next 36+ hours.

[ShawniganLake]

The WRF is currently showing more snow over Victoria in the next 48 hours than there has been in the past 4 years. That said the snowfall totals it's shown over the Island have been pretty inconsistent. It hasn't made up its mind on whether things are going to stall and dump over East Vancouver Island, or slide south and given widespread totals of 2"+. I've learned to be skeptical of the totals this model shows, often it underdoes it in the initial snow for full on Arctic blasts and overdoes it in more marginal/overrunning situations. This time it's a tough call because this is setting up to be more of a hybrid, not quite a traditional Artic blast but much colder than the more typical marginal events where the WRF shows large accumulations with 925mb temps never falling below -2C.

 

http://www.atmos.washington.edu/wrfrt/data/2016120412/images_d4/wa_snow48.48.0000.gif

I like the purples near Shawnigan lake.

[Phil]

So..here's how mid/late December could overperform all expectations, via a troposphere/stratosphere PV coupling right over west/central Canada.

 

Some modeling (including the 12z GFS/GEFS) sends WAFz into the stratPV via the NATL, following the ongoing CW event. So, mass flux increases upon propagation into western Eurasia, and an appendage of the PV strengthens over west/central Canada following the wave2 cycle response.

 

So, when we cycle from wave2 back into wave1, the dominant PV lobe consolidates over western Canada, while the Eurasian portion of the PV gets blasted. So, via that GOA/EPO ridge, the big vortex in west/central Canada can couple with the PV there while the wave1/MT shot out of Eurasia bombards the polar domain with WAFz/blocking, forcing the entire lower PV column into western Canada.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/5309EB33-342B-4F03-890F-10DB6F57E9D0_zpsdptzbzow.jpg

 

Then we'd have a mostly coupled PV sitting somewhere in the vicinity of Alberta, possibly ready to unload over the region if we can keep wave driving/blocking going. So while we'd be playing with possible +EPO fire if the wave driving fails, it could also turn into something historic if everything is of sufficient amplitude and is timed properly.