December 2015 in the Pacific Northwest

[ShawniganLake]

Looks like there is potential for a Hood Canal snow event early next week, with a fairly potent low tracking into the central Washington coast. 

[Brennan]

I think part of the excitement and the fun for me resides in the fact that at least something sort of interesting is happening (Huge mountain snows, tons of lowland rainfall, mini surprise lowland wet snow non-event), and something interesting is at least possible in the future (more epic mountain snow, possible lowland snow, no sign of death ridge etc,). When this community is active, it almost feels enchanted. I just hope we can all come out of this winter with something to hang our heads on. 

[Bryant]

The ECMWF is close to being excellent.  Bitterly cold air is shown quite far south in BC on this run.  Besides that the basic setup is still good at day 10.  This looks pretty promising to me.

 

I'm really curious to see how things play out in the next 10+ days. From a tropical perspective, this current forcing over the Maritime looks to wane around Christmas time (+/- a few days), with forcing shifting back over the dateline region due to the El Nino standing wave we've seen since November. If this progression comes to fruition, then tropical forcing would favor an Aleutian low / high zonal pattern similar to the first half of December.

 

However, looking at the Medium/Long range ensembles, troughing is locked in over Greenland the whole run, keeping the east coast ridge in full force. If we start to see heights push into that region, that's when the overall pattern will begin to favor the east imo. LR ensembles obviously smooth out the overall pattern, but there are no signs of any pattern change on the horizon currently from a 500mb perspective. With that said, we see a dominant Scandinavian ridge shown to persist on the models which will promote more PV disruption, allowing more potential to tap into arctic air if given the opportunity.  

[seattleweatherguy]

Me too. It is interesting to note the long range models continue to show the main torching being in the East. I guess we were due for something like this since the East has stolen the show so many times when it should have been our turn.

Then we need a super south east ridge to get historic cold?

[SilverFallsAndrew]

Crap, 2.30" of rain at SLE today

[snow_wizard]

It's interesting to see how much more negative the ECMWF based PNA forecast is than the GFS.  ECMWF shows sustained values around -3 for the next 10 days.  It also shows the EPO dropping to zero.

[snow_wizard]

It was a pretty raw day here today as some of the cold from the passes seeped into this area.  It's been around 37 and raining for hours now with a decent easterly breeze.

[BLI snowman]

3rd day this month with at least 2" of rain at VUO. I'm just under 14" now for the month.

[BLI snowman]

The signs pointing towards the establishment of a Columbia Basin cold pool at the absolute peak of our inversion season (last week of December) are very encouraging.

 

Historically, it can snow so easily here in late December when that gets going and gradients remain slightly offshore. Late December is a good time of the year.

[Gradient Keeper]

I'm really curious to see how things play out in the next 10+ days. From a tropical perspective, this current forcing over the Maritime looks to wane around Christmas time (+/- a few days), with forcing shifting back over the dateline region due to the El Nino standing wave we've seen since November. If this progression comes to fruition, then tropical forcing would favor an Aleutian low / high zonal pattern similar to the first half of December.

 

However, looking at the Medium/Long range ensembles, troughing is locked in over Greenland the whole run, keeping the east coast ridge in full force. If we start to see heights push into that region, that's when the overall pattern will begin to favor the east imo. LR ensembles obviously smooth out the overall pattern, but there are no signs of any pattern change on the horizon currently from a 500mb perspective. With that said, we see a dominant Scandinavian ridge shown to persist on the models which will promote more PV disruption, allowing more potential to tap into arctic air if given the opportunity.  

Great post and insight.

[Gradient Keeper]

The signs pointing towards the establishment of a Columbia Basin cold pool at the absolute peak of our inversion season (last week of December) are very encouraging.

 

Historically, it can snow so easily here in late December when that gets going and gradients remain slightly offshore. Late December is a good time of the year.

Exactly my thoughts.

[Gradient Keeper]

It's interesting to see how much more negative the ECMWF based PNA forecast is than the GFS.  ECMWF shows sustained values around -3 for the next 10 days.  It also shows the EPO dropping to zero.

Encouraging

[BLI snowman]

Exactly my thoughts.

 

As an example of what I mean, the Euro actually isn't too far off right now from what we saw the last week of December 1992. That packed a tight little pressure gradient so there was some strong Fraser River outflow but it wasn't a huge upper level event by any means. Just a solidly cool trough with a deepening inversion that got going at the right time. A low tracked offshore on New Year's Eve and gave NW OR and SW WA a nice snowstorm.

[Bryant]

Great post and insight.

 

Appreciate it DJ. Always appreciate the time you take to analyze the models for us, good or bad. 

[Bryant]

As an example of what I mean, the Euro actually isn't too far off right now from what we saw the last week of December 1992. That packed a tight little pressure gradient so there was some strong Fraser River outflow but it wasn't a huge upper level event by any means. Just a solidly cool trough with a deepening inversion that got going at the right time. A low tracked offshore on New Year's Eve and gave NW OR and SW WA a nice snowstorm.

 

What are your thoughts for the BLI region? Seems like we are in one of the better locations just because it's a borderline setup as of now and outflow can work wonders, but I'm really unsure at this point

[BLI snowman]

What are your thoughts for the BLI region? Seems like we are in one of the better locations just because it's a borderline setup as of now and outflow can work wonders, but I'm really unsure at this point

 

As the aforementioned 1992 event and others prove, all you need is offshore gradients and an arctic boundary to traverse the eastern Fraser River valley for Whatcom County to get decent seepage. BLI had a 24/20 day with that event in spite of 850mb temps bottoming out around perhaps -9c.

 

No guarantees that that sort of thing will happen, but the last two Euro runs have been flirting with it and it doesn't take a whole lot of tweaking to deliver respectably cold temps when some of the main ingredients look to be in play.

[Deweydog]

As the aforementioned 1992 event and others prove, all you need is offshore gradients and an arctic boundary to traverse the eastern Fraser River valley for Whatcom County to get decent seepage. BLI had a 24/20 day with that event in spite of 850mb temps bottoming out around perhaps -9c.

 

No guarantees that that sort of thing will happen, but the last two Euro runs have been flirting with it and it doesn't take a whole lot of tweaking to deliver respectably cold temps when some of the main ingredients look to be in play.

Reminds me more of late December 2003, at least conceptually. 1992 was an impressive Arctic air mass which just happened to dig too far offshore, similar to January 2005 at the onset. It was actually a pretty significant bust as 4-5 days out it was progged to be a direct hit.

[Gradient Keeper]

Appreciate it DJ. Always appreciate the time you take to analyze the models for us, good or bad. 

Thanks and likewise all of your information and knowledge.

[DareDuck]

I've seen blowing snow every year I've lived in central Oregon. This year probably 3 tomes so far. I've lived here 6 years now and it's such a great place to live weather wise. It's a lot slower than being in Ne PDX.

I agree with this all. I wasn't expecting much down here with El Niño but I'm already at 18" this season and snow cover on the ground for 11 days.

[BLI snowman]

Reminds me more of late December 2003, at least conceptually. 1992 was an impressive Arctic air mass which just happened to dig too far offshore, similar to January 2005 at the onset. It was actually a pretty significant bust as 4-5 days out it was progged to be a direct hit.

 

I certainly wouldn't call it impressive from a verification standpoint. No one in the lower 48 had a significantly cold upper level arctic airmass with it, 510 thickness barely moved into MT and ND. The PV was pretty stacked in December 1992 and a lot of that cold stayed bottled up, not too unlike this month but I'd wager it was significantly more -EPO. 

[Deweydog]

I certainly wouldn't call it impressive from a verification standpoint. No one in the lower 48 had a significantly cold upper level arctic airmass with it, 510 thickness barely moved into MT and ND. The PV was pretty stacked in December 1992 and a lot of that cold stayed bottled up, not too unlike this month but I'd wager it was significantly more -EPO.

It definitely split like a mofo. Turned into a hybrid, monster ULL.

[crf450ish]

Good morning folks! Got up @ 3:30 to do what humans do when they drink too much water and noticed its STILL snowing!!!! HAHA this is AWESOME! I stepped outside and measured 4" on my sidewalk, that I shoveled at 9pm, guessing theres at least 8" on the ground right now. This is badass! And theres more forecasted too, haha! WOW! 

 

 

Just driving around some service/reservation roads near lake roosevelt yesterday and came across these cool old fallen trees: 

 

 

 

Ok, I have no idea how or why they are rotated like this......they are completely normal on my computer....

[Gradient Keeper]

Good morning. I wish I had good news on the GFS side of things, but I do not. The 6z was probably the worst GFS run in days. Even though we still likely develop a persistent Columbia Basin cold pool as the ridge slides inland. At HR 84 the wave that develops off Asia strengthens does too far east before the ridge over the Aleutians can build and amplify which shoves the ridge east very quickly. Very progressive. This is a trend with the GFS that can't be ignored. Also, the bitterly cold deep air is bottled up north not really making much progress southward out of Yukon-Northwest Territories. At the same time the 6z GFS 6-10/8-14 day Composite Analog reveals fairly low correlation scores, so it's possible the GFS is just not handling the upper level pattern correctly. On the other side of things the ECMWF past several runs has its own trend of developing the low off Asia further west allowing the ridge to amplify nicely. I would say the EURO has shown the most run to run consistency. The GEM also is showing this. We are getting towards that time frame where one of the model camps is going to blink. The GFS either trends towards the EURO/GEM, or they trend unfavorably towards the GFS. We don't know this yet. With an overall progressive pattern my concern is they might do that. Onto 12z!

[TT-SEA]

Cold air is hard to dislodge... wind never came last night.   

 

Still 34 here with most of our snow left.

[Tyler Mode]

Closing in on a foot here.  Of rain. 

 

Most areas are over that by now. 

 

Cold air was dislodged last night between 8 pm and 9 pm.  Temp went from 41 to 51 during that time.

[bainbridgekid]

Alpental is opening today with a base depth of 52" and growing.

[jcmcgaffey]

Driving over snoqualmie pass looks fun right now...

[Gradient Keeper]

12z GFS has begun..

Will the GFS trend towards the EURO or will it continue to be more progressive with the ridge.

[Gradient Keeper]

Driving over snoqualmie pass looks fun right now...

Yeah it sure does

[Front Ranger]

The 6z GFS did show a low taking an interesting track at day 6. Not a lot of cold air to draw from at face value, but still.

 

 

[Gradient Keeper]

The 6z GFS did show a low taking an interesting track at day 6. Not a lot of cold air to draw from at face value, but still.

 

get_orig_img.png

Yeah, I noticed that too. If there is any cold air in the Columbia Basin that could prove interesting.

[Front Ranger]

FWIW, 0z Euro ensembles were strongest yet with the offshore ridge days 4-8. Days 9-10, they were a little weaker than the 12z ensembles with trying to re-establish.

[MR.SNOWMIZER]

Looks like there is potential for a Hood Canal snow event early next week, with a fairly potent low tracking into the central Washington coast. 

Yeah i noticed that also. I have had some huge snow events with that pattern. This year reminds me of 2007 winter just warmer. I had 42 inches of snow that year and 54 the next winter. Last three winters here have been terrible.

[Gradient Keeper]

12z GFS  HR 72 all eyes on the 1019mb wave

 

http://www.tropicaltidbits.com/analysis/models/gfs/2015121812/gfs_z500_mslp_wpac_13.png

[Gradient Keeper]

Model comparison. Low is developing where previous GFS runs had it and south of where the EURO projects it. May not be any changes with this GFS run. We'll know in the next few frames.

[Front Ranger]

At day 4 on the 12z, ridge is in a little better position and more tilted. Colder already for the PNW.

[Gradient Keeper]

HR 102 low is deeper on this run compared to previous 6z, 00z GFS. Maybe a tad further west.

[Tyler Mode]

Another one year ago comparison with snow depth at Paradise on Mt. Rainier. Quite a huge change!

 

 

[Front Ranger]

This GFS run is definitely making a move towards the Euro. More energy held further west in the Aleutians, resulting in stronger ridge amplification offshore,

[Gradient Keeper]

HR 120 low south of Aleutians is much stronger and a good 300 miles further west from 6z, 00z. Might be slightly better amplification of ridge.

 

http://www.tropicaltidbits.com/analysis/models/gfs/2015121812/gfs_z500_mslp_namer_21.png