jaya

Agreed. Op run at low res beyond 192 always shoots cold air sw. It also undercuts blocks too quickly. Go parallel.

If this does happen, there will be many - many happy and busy plumbers in western WA and OR. I should have gone into a different line of work - but that is a messy job.

Unfortunately! We have gotten used to model runs that exhibit quite a bit of skill out 7 days or more. But there are some patterns that are inherently unstable (like the one we are in) and -- models are only models.

Look at the differences between all the models N of HI and S of the Aleutians... toggle through the 0 Hr fcsts at http://www.tropicaltidbits.com/analysis/models/?model=gem&region=namer&pkg=z500_mslp&runtime=2014122712&fh=-12&xpos=0&ypos=0. The short term problem will be low development just off the coast - how much, where, track). Ensembles all now say that it will get cold in western Washington. Concerning the extended, no clue - and little in the way of any skill. Models are going to take several runs to resolve.

No, but I'm saying that it is a possibility. Won't know until the last minute.

I really like Cliff Mass and the work he and his students/coworkers have done with mesoscale modeling here in the northwest. But the WRF has issues that have not and seemingly cannot be resolved yet. First, it mixes too much energy downward. That is why we won't see good northerly winds in this situation in the Puget Sound. Second, it seems to produce too much downslope warming even in somewhat stable situations. Then, there is the issue of using the operational GFS as a lateral boundary (this model really misses things on occasion over the all important central and northwest Pacific in these situations). Winds don't look strong enough in the Fraser outflow area (it can get this right on occasion - but not always). Winds with the initial surge are typically too easterly (over mixing of geostrophic flow downward?) I remember some situations (I get the dates mixed up now as I age) where the NAM - despite its poor initialization using an early data cutoff - beats the WRF with wind directions, mixing, and convergence boundaries including the strength of the arctic front. I am thinking Nov 2009 or 2010 (can't remember). I look at it, think about it, then look at lots of other things giving the WRF a bit of weight but not all in like some others.

I see a lot of posts that seem to be over analyzing (or weather porn watching) the models and getting depressed or excited from run to run. The big problems occur early on in the model run. For myself, I'll be watching satellite over the central Pacific to see what the structure is of the low north of Hawaii...that is the player. There are other problems further NW. Unfortunately, at home I don't have as many resources available to me.

Toggle between the GFS and the parallel GFS at this time frame http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=namer&pkg=z500_mslp&runtime=2014122712&fh=120&xpos=0&ypos=0. Notice the handling in the western Gulf of Alaska. Where is the deep low that you see on the parallel on the operational? Huge implications and that is where the big ensemble spread is originating (actually further south early on). Initialization from satellite can only do so much (it has gotten impressive but isn't everything). I have found that model performance can be better in the 7-10 day period than the day 5 period (then increases again in the short term). Could this be due to the void/quality of the initialization in the central Pacific in these situations? Seems to be. But there are so many unknowns. Maybe NOAA will fly some recon flights between Hawaii and Alaska (though I haven't seen anything on this during the current year).

Look at the baroclinicity around Seattle. If this were to happen - Seattle watch out. But, we'll see.

I have found the WRF to underperform when flow is onshore (arctic boundaries and CZs) and to over perform in overrunning events (S Interior and Shelton area). I no longer give a great deal of thought to this model when we are moving into a cold event. It is pretty good (though overdone) with heavy rainfall events.

Don't get excited or depressed. After a quick look at the 12z and last night's solutions...the operational GFS and last nights Canadian seem to be meshing various low pressure systems into one north of Hawaii, the GFS Parallel does not (likely more realistic). The bad thing is that these small features in the middle of no where will be very difficult for any solution to pick up on, then handle properly. Details on exactly how strong and where the low(s) set up and move will be critical to downstream ridge placement and amplification. I'd just say that there is massive POTENTIAL after hr 144 - but nothing is set one way or another. In the shorter term, snow for the Puget Sound area looks most likely to be light, but even SMALL differences in the amount of development we get off Vancouver Island and western WA (this is dependent on how much and how fast cold air spills offshore) can mean the difference between a flurry before things get dry and a few inches (possibly local) with an arctic boundary that looks like a convergence zone.

It really was kind of local from east of Paine field to Evergreen and from just north of the Boeing Expressway southward about 2 miles or so.

Yep

I got lucky and got nearly 6 inches out of that one! Granted--I live over 600 ft in the CZ area and usually do well with snow.

Canadian GEM is golden if you like good snow in Puget Sound - for sure!

Hmmmm, pcpn map is out. interesting. http://www.tropicaltidbits.com/analysis/models/?model=gem&region=wus&pkg=mslp_pcpn&runtime=2014122700&fh=54

Second cold shot is not a lock...http://www.tropicaltidbits.com/analysis/models/?model=gfsp&region=namer&pkg=z500_mslp&runtime=2014122700&fh=150&xpos=0&ypos=0. But, at least we are looking at another arctic in the short term and had something in November. Two in a year with a neutral-warm ENSO isn't bad.

Certainly a plausible solution as the ridge tries to retrograde and pinch off. The parallel run does not do this: http://www.tropicaltidbits.com/analysis/models/?model=gfsp&region=namer&pkg=z500_mslp&runtime=2014122700&fh=120but seems to lose some southward punch of the short wave...and that would track energy eastward along the Canadian border and keep things mild and onshore in the PNW.

The Der Niederschlag is the most important chart I've seen today! http://www.wetterzentrale.de/pics/MT8_Seattle_USA_ens.png. All cold and tight in the short term (don't worry about the long term -- too far out especially for the operational dumb-down GFS beyond 192.

Well, I don't know about shutting Seattle down with an inch - unless people decide to start driving in normal Seattle fashion. But then you can do that with a light drizzle around here.

Very small differences in the over water trajectory will impact low development and the strength of any arctic front in the interior. No one should hold out hope...no mater what the models look like, until the event is nearly underway.

Looking at the gradients, any snow you get will be between Bellingham and Orcas Island in the Salish sea.

Probably not a lot...but an inch or so isn't out of the question.

The block tilting toward Yukon will spill more cold air just off shore and give some low development. The various models pick up on this type of feature but typically mishandle the amount of development that can take place.

No one really knows yet...it is in beta. But overall it has been looking better performance wise.