December 2014 Observations for the Pacific Northwest

[snow_wizard]

Looking at the ECMWF again...it really is spectacular at day 10. It strongly suggests a major long lasting cold wave if it verifies. Very likely there would be snow somewhere in the 8 to 10 day period if it verifies.

[Gradient Keeper]

I just looked at individual members of the GEM HR 204-240 ....

Look much improved... Many cold, some bitter, some even put the PV over south-central BC and have heights around 510-520 over PDX-BLI...

[Bryant]

Problem is, it's mature by the time the pattern attempts to right itself late next week. The Euro really went crazy with keeping the Kona low cut off and meandering while everyone else seems to like the idea of westerlies undercutting, hence taking the block out of play for most. This seems like the most plausible scenario as there isn't much precedent for a solid, backdoor modified event/slop over ridge combo then leading to a secondary full latitude retrogression. December 2008 kind of did it, but it was a very quick evolution, not nearly as protracted as this one would be.

 

Obviously nothing is off the table at this point, but a clash of air masses in a deamplifying pattern seems more likely to me. We'll see.

I definitely agree that a deamplifying pattern seems to be the most likely, but the pattern does show massive potential. If the pattern evolution matched the 00z Euro from tonight, it definitely appeared that the trough would dig further west if we were to extrapolate the pattern. The anomolous high pressure in Alaska may not budge, but the base of the ridge just needs to buckle ever so slightly to allow an over water trajectory and huge snow potential. Granted, I'm referring to la-la land

[snow_wizard]

I definitely agree that a deamplifying pattern seems to be the most likely, but the pattern does show massive potential. If the pattern evolution matched the 00z Euro from tonight, it definitely appeared that the trough would dig further west if we were to extrapolate the pattern. The anomolous high pressure in Alaska may not budge, but the base of the ridge just needs to buckle ever so slightly to allow an over water trajectory and huge snow potential. Granted, I'm referring to la-la land

I think the models are responding to the expected strong MJO wave progged for octant 5. Nice territory for us. I think this ECMWF run and the Canadian ensemble, and even the GFS ensemble to some extent have lessened the idea of a de-amplification.

[Deweydog]

I definitely agree that a deamplifying pattern seems to be the most likely, but the pattern does show massive potential. If the pattern evolution matched the 00z Euro from tonight, it definitely appeared that the trough would dig further west if we were to extrapolate the pattern. The anomolous high pressure in Alaska may not budge, but the base of the ridge just needs to buckle ever so slightly to allow an over water trajectory and huge snow potential. Granted, I'm referring to la-la land

 

It's got great potential, but potential can be well-seasoned by past performance.  The Euro solution, although still not all that impressive at day 10, unless you consider a maritime-polar clipper with some overrunning potential worthy of a touchdown dance, is obviously a best-case scenario.  It leaves the door open in a situation where the conventional wisdom is that the door is typically closing.  January 1950 or January 2005 redux!  

[snow_wizard]

BTW I have to give serious kudos to Phil. He nailed this thing between the eyes.

 

I think I did ok too, but in more general terms.

[Bryant]

I think the models are responding to the expected strong MJO wave progged for octant 5. Nice territory for us. I think this ECMWF run and the Canadian ensemble, and even the GFS ensemble to some extent have lessened the idea of a de-amplification.

MJO has proven to be a big player this year. Almost been too easy to highlight potential timeframes

[snow_wizard]

It's got great potential, but potential can be well-seasoned by past performance.  The Euro solution, although still not all that impressive at day 10, unless you consider a maritime-polar clipper with some overrunning potential worthy of a touchdown dance, is obviously a best-case scenario.  It leaves the door open in a situation where the conventional wisdom is that the door is typically closing.  January 1950 or January 2005 redux!

Indeed. Where the ECMWF is sitting at day 10 it could tap into some REAL cold in a short time.

[snow_wizard]

MJO has proven to be a big player this year. Almost been too easy to highlight potential timeframes

Yup...both major waves have delivered.

 

I'm surprised the NWS hasn't talked more about wind up your way. Those gradients look impressive.

[ShawniganLake]

They haven't.  

So why all the sadness this afternoon?

[Deweydog]

So why all the sadness this afternoon?

 

You'll have to ask each individual sadist.  

[Gradient Keeper]

Alright..... exhausted going to bed. Won't be here for 6z.... It would be nice to see 6z GFS get on board. Cya for 12z.

[snow_wizard]

The WRF is showing a pretty rare situation for the Puget Sound region once the cold air is in place. It shows a 4mb W to E pressure gradient west of the Cascades and a rather strong easterly gradient east of the Cascades. As a result it shows the easterly winds that would normally blow in King County being pushed down into Pierce County. It will be kind of interesting to see how that plays out.

[Bryant]

Yup...both major waves have delivered.

 

I'm surprised the NWS hasn't talked more about wind up your way. Those gradients look impressive.

Yeah the outflow will definitely be felt by all up here. Hope to see some surprises with this.

[seattleweatherguy]

I just looked at individual members of the GEM HR 204-240 ....

Look much improved... Many cold, some bitter, some even put the PV over south-central BC and have heights around 510-520 over PDX-BLI...

that prob puts seattle on that model at 498...

[Bryant]

So why all the sadness this afternoon?

Some members consider a model run or two a trend, and while it may be true sometimes, this time is definitely not the case.

[seattleweatherguy]

The WRF is showing a pretty rare situation for the Puget Sound region once the cold air is in place. It shows a 4mb W to E pressure gradient west of the Cascades and a rather strong easterly gradient east of the Cascades. As a result it shows the easterly winds that would normally blow in King County being pushed down into Pierce County. It will be kind of interesting to see how that plays out.

That sounds like Tacoma being the conversion zone area or maybe two different conversion zones forming?

[snow_wizard]

That sounds like Tacoma being the conversion zone area or maybe two different conversion zones forming?

No...this is after the Arctic air has arrived and is still pouring in. I think the westerly gradient between the Olympics and the Cascade crest will be due to strong Fraser outflow pressurizing the Puget Sound basin. The Cascades will have cold air rushing in from both sides of the range.

[seattleweatherguy]

No...this is after the Arctic air has arrived and is still pouring in. I think the westerly gradient between the Olympics and the Cascade crest will be due to strong Fraser outflow pressurizing the Puget Sound basin. The Cascades will have cold air rushing in from both sides of the range.

okay thanks sorry learning. so what can this mean for the puget sound region good or bad?

[snow_wizard]

that prob puts seattle on that model at 498...

There is one extremely cold ensemble member that goes below -20C.

[snow_wizard]

okay thanks sorry learning. so what can this mean for the puget sound region good or bad?

It really doesn't mean a whole lot except some areas that might normally have east winds might go calm and get a lot colder than they normally would due to decoupling of the atmosphere. It's just kind of an oddity.

[snow_wizard]

I actually pulled off a 42-33 high/low today. Felt downright cold!

[seattleweatherguy]

There is one extremely cold ensemble member that goes below -20C.

That would be awesome. That may cause Lake Washington to freeze again.

[ShawniganLake]

I actually pulled off a 42-33 high/low today. Felt downright cold!

39/31 here today.  Hasn't been as torchy over here as some other places in the region have been this month.  9 freezes so far. 

[bainbridgekid]

I actually pulled off a 42-33 high/low today. Felt downright cold!

Even SEA pulled off a 42/35.

 

Definitely felt chilly after all the warmth we've been having.

[ShawniganLake]

http://vortex.accuweather.com/adc2004/pub/includes/columns/community/2014/590x382_12261533_hisnow1225a.jpg

[snow_wizard]

The ECMWF ensemble certainly shows the second cold shot. It looks a bit better than the 12z so the trend is good.

[bainbridgekid]

The ECMWF ensemble certainly shows the second cold shot. It looks a bit better than the 12z so the trend is good.

Yeah definitely in good agreement with the operational. Left image is the ensemble mean and the right one is the operational for hour 192.

 

http://download.ecmwf.org/data/web249/get_legacy_plot-web249-20141227092014-28087-2078.gif

[MikeInEverett]

FWIW: weather.com is going all in with snow for me in Snohomish next weekend and early next week. Highs in low 30s with 3-5 inches, lol.

[Snow]

[MikeInEverett]

Good morning. I just looked at the latest GFS Ensembles and it's a SCORE! ❄

 

Here is the Vancouver BC ensembles, it shows the Arctic air more easily but PDX and SEA will also do.

 

http://oi61.tinypic.com/6p56p4.jpg

I'm starting to feel more and more confident about a widespread PNW snow next weekend going into next week. 

[Snow]

[TT-SEA]

00Z ECMWF precip map was certainly a disappointment.

 

Very light precip on Sunday when its just a little too warm for snow even here... and then Sunday evening when its finally cold enough the precip shuts off completely from Tacoma northward.

[SilverFallsAndrew]

Yeah me too and here are the ensembles for Yakima. It's worth posting because it can tell us if the Arctic air is able to cross the Canadian border towards Oregon and snuggle up right next to the Cascades. As you can see it sure does!

 

http://oi57.tinypic.com/290xzdc.jpg

 

Can you post PDX?

[SilverFallsAndrew]

At this point I think up to 2" is possible at my location late Sunday night and Monday morning. 

[Snow]

Can you post PDX?

Sure, here it is.

 

http://oi58.tinypic.com/2a0ksoy.jpg

[SilverFallsAndrew]

Sure, here it is.

 

http://oi58.tinypic.com/2a0ksoy.jpg

 

Thank you sir. Not bad. The "reload" does appear to show a bit of a N/S gradient, but yeah a good ensemble trend.

[MR.SNOWMIZER]

I can smell a sloppy overrunning event coming.

[Snow]

Thank you sir. Not bad. The "reload" does appear to show a bit of a N/S gradient, but yeah a good ensemble trend.

Your welcome. It should be plenty cold enough Salem North. Plus it looks like Yakima will be a little colder 850mb temp wise than Vancouver BC so the Gorge will definitely be pumping in the Arctic air to the Valley. Everybody has a great chance of scoring in this set-up.

[SilverFallsAndrew]

12z NAM

 

http://mag.ncep.noaa.gov/data/nam/12/nam_namer_054_500_vort_ht.gif