December 2020 Weather Observations for the PNW

[Gradient Keeper]

1 minute ago, SilverFallsAndrew said:

Yeah I mean you know how it goes. It’s definitely not as funny as it used to be, kind of gets old after a while. Running out the same material for 10+ years. Your group is by far the better group for actually discussing weather. A serious weather post in that group gets like 3 comments, a post about the looks of some new weather anchor gets about 30, they’ve been having a lot of trouble with getting zucked lately. 

Yep, I certainly do, and that's why I still have quite a few of them blocked for something like 8 years now? maybe longer. Unbelievable. I'm really surprised that group has survived, but more so hasn't been banned. I'm even more surprised that any pro mets would waste a second of their time there. It's mind boggling to me.

18z GEFS (Pivotal) in 12 minutes

[jakerepp]

8 minutes ago, hawkstwelve said:

Probability of some amount of snow for varying Western WA locales by 10AM Tues per 12z EPS...

KBLI: 48% (Avg: < 1 in.)

KPAE: 70% (Avg: 1.5 in.)

KSEA: 66% (Avg: Just a little over 1 in.)

KPLU: 88% (Avg: 2.5 in)

KOLM: 54% (Avg: Just a little over 1 in.)

Certainly not bad chances overall. Included Pierce County/Thun Field in there as I've found it's a fairly good representation for South Sound foothill areas. A little surprised to see it's higher chance than Everett, given CZ signatures that have shown up in some runs. 

We shall see soon enough.

18z GFS showed the CZ centered around DT Seattle and skunking us in Snohomish county for the most part. 

[bainbridgekid]

18 minutes ago, jakerepp said:

18z GFS showed the CZ centered around DT Seattle and skunking us in Snohomish county for the most part. 

It's much more common for models to show the CZ too far South than the other way around. Best odds are definitely still in Snohomish County and East of 405 further South.

[AbbyJr]

57 minutes ago, DJ Droppin said:

Seeing absolutely nothing on any ensembles supporting a glimmer of hope for Cold and SNOW! now pushing out into January is becoming a bit discouraging. I know things can change quickly, but when we go through another and another 7-10 day period saying the same things you start to move through the 'heart' of Winter rather quickly. I may receive a rare 'weenie' tag for this. I'm just being realistic. For PDX/Gorge there is always the outside chance of the pattern setting up to allow for decent low level cold to build over the Columbia Basin and then east winds with systems approaching from the southwest to pull in enough colder/drier air for localized fun. Who knows.

00z GFS in 5 hours 7 minutes

A solid chance of a major SSW event early January doesn't give you any hope for cold and snow?

[SouthHillFrosty]

30 minutes ago, hawkstwelve said:

Probability of some amount of snow for varying Western WA locales by 10AM Tues per 12z EPS...

KBLI: 48% (Avg: < 1 in.)

KPAE: 70% (Avg: 1.5 in.)

KSEA: 66% (Avg: Just a little over 1 in.)

KPLU: 88% (Avg: 2.5 in)

KOLM: 54% (Avg: Just a little over 1 in.)

Certainly not bad chances overall. Included Pierce County/Thun Field in there as I've found it's a fairly good representation for South Sound foothill areas. A little surprised to see it's higher chance than Everett, given CZ signatures that have shown up in some runs. 

We shall see soon enough.

Which one is Thun Field? I live right by it but have never known airport acronym thing

[bainbridgekid]

6 minutes ago, SouthHillFrosty said:

Which one is Thun Field? I live right by it but have never known airport acronym thing

KPLU.

[MossMan]

Dark and raining currently. 

[bainbridgekid]

First mention of the S-word in the afternoon AFD.

"An area of low pressure will develop along the draped front in the Pacific and slide northeast towards the area late Sunday into Monday. This is where the forecast becomes a bit more interesting as to the track of the Monday system. Guidance has shifted a south in regards to the Monday system allowing for colder air to filter in on the backside of the area of low pressure. With that said, there is still uncertainty in the exact track, with ECMWF and most ensembles tracking on the southern edge of guidance (HQM to OLM and east), while GFS and ensemble mean more along the lines of UIL to PAE. Though this may not seem to significant, this does play a role in the precipitation type across areas of Puget Sound and how quickly cold air filters in prior to precipitation shutting off Monday night. All that said, there will be at least the potential for localized snow to mix in Monday afternoon to Monday evening. The main areas of focus currently would be the Foothills and near any convergence zone across the central Puget Sound. The area to most closely monitor for any snow accumulation may be the northern Olympic Peninsula where upslope flow and cold air may increase the potential."

[Esquimalt]

Wow the HRDPS is extremely close for me.  What are we looking at for the 18Z euro?

[Deweydog]

26 minutes ago, MossMan said:

Dark and raining currently. 

Getting darker here too.  Raining as well.

[Timmy]

1 minute ago, Deweydog said:

Getting darker here too.  Raining as well.

Will probably get lighter and less rainy at some point.

[Meatyorologist]

3 minutes ago, Esquimalt said:

Wow the HRDPS is extremely close for me.  What are we looking at for the 18Z euro?

Lower than the 12z, but that was an unrealistic scenario anyways. I'd say this is still on the high end.

[Gradient Keeper]

46 minutes ago, AbbyJr said:

A solid chance of a major SSW event early January doesn't give you any hope for cold and snow?

Sure, if it actually occurs. Is there solid agreement with the GEFS AND EPS? or is the GEFS on its own? It initially was mid-December for the big pattern change, then it was pushed back, and pushed back further. I'll believe it when I see it.

[Jbolin]

6 minutes ago, Timmy said:

Will probably get lighter and less rainy at some point.

Sometime around early to mid April is my and likely Dewey's response as well given that sun angles are much higher then. 

[The Swamp]

4 minutes ago, DJ Droppin said:

Sure, if it actually occurs. Is there solid agreement with the GEFS AND EPS? or is the GEFS on its own? It initially was mid-December for the big pattern change, then it was pushed back, and pushed back further. I'll believe it when I see it.

I don't see anything special through mid-January.  This Nina may end up being super back loaded with lots of wet slop marginal snow in March and April, if at all.

[Esquimalt]

10 minutes ago, Meatyorologist said:

Lower than the 12z, but that was an unrealistic scenario anyways. I'd say this is still on the high end.

That’s 3 times the 12Z for me. I’ll take it!!

[Winterdog]

What’s this negative Nancy stuff, my Davis weather app says snow on Christmas!

[MossMan]

17 minutes ago, hawkstwelve said:

 

I’m in the white! 

[Gradient Keeper]

Snowman Building Contest/Event Extravaganza!

ANYONE whom lives in Western Washington that receives snow Monday MUST build a snowman and take pics/videos to which you will then share with the rest of the Forum! Yep! It doesn't matter how small nor tall it is. C'MON this will be fun and painful too for those of us down south stuck in the warm muck.

[snow_wizard]

18 minutes ago, hawkstwelve said:

Definitely a fair amount less than the overly snowy 12z.

This is probably more realistic, if it happens.

It will be interesting to see how it plays out.  The 18z GFS was quite a bit better for us than the 12z.  Looks like some snow is a realistic possibility.

[Meatyorologist]

2 minutes ago, DJ Droppin said:

Snowman Building Contest/Event Extravaganza!

ANYONE whom lives in Western Washington that receives snow Monday MUST build a snowman and take pics/videos to which you will then share with the rest of the Forum! Yep! It doesn't matter how small nor tall it is. C'MON this will be fun and painful too for those of us down south stuck in the warm muck.

Fine, but not because you told me to! 

[MossMan]

1 minute ago, DJ Droppin said:

Snowman Building Contest/Event Extravaganza!

ANYONE whom lives in Western Washington that receives snow Monday MUST build a snowman and take pics/videos to which you will then share with the rest of the Forum! Yep! It doesn't matter how small nor tall it is. C'MON this will be fun and painful too for those of us down south stuck in the warm muck.

I’m there! However NWS Seattle thinks I will get zero snow.

[snow_wizard]

It does appear Clallam County could get hit pretty hard with the snow.  Even the NWS mentioned that.

[Deweydog]

36 minutes ago, DJ Droppin said:

Sure, if it actually occurs. Is there solid agreement with the GEFS AND EPS? or is the GEFS on its own? It initially was mid-December for the big pattern change, then it was pushed back, and pushed back further. I'll believe it when I see it.

Take it for FWIW, but the signal for a traditional PNW cold pattern, ie significant GOA blocking of a “locked” variety has never really existed in the models to this point.  Lots of transitory stuff in a mainly progressive pattern.  

[Gradient Keeper]

7 minutes ago, Deweydog said:

Take it for FWIW, but the signal for a traditional PNW cold pattern, ie significant GOA blocking of a “locked” variety has never really existed in the models to this point.  Lots of transitory stuff in a mainly progressive pattern.  

Yep. No real persistent blocking since October if I'm not mistaken.

[Canadian guy]

9 minutes ago, Deweydog said:

Take it for FWIW, but the signal for a traditional PNW cold pattern, ie significant GOA blocking of a “locked” variety has never really existed in the models to this point.  Lots of transitory stuff in a mainly progressive pattern.  

You still think favourable blocking will take shape sometime in January?

[Meatyorologist]

1 minute ago, Canadian guy said:

You still think favourable blocking will take shape sometime in January?

If you asked @Phil he'd probably say yes. As for the rest of us, no idea.

[bainbridgekid]

NWS forecast for the Cascades might need an update . . .

Monday: Rain and snow. Snow level near 5500 feet. Rainfall amounts one to three inches possible. Afternoon pass temperatures in the mid to upper 30s. South wind in the passes around 10 mph becoming southwest in the afternoon.

[FroYoBro]

It’s raining! 

[Deweydog]

24 minutes ago, Canadian guy said:

You still think favourable blocking will take shape sometime in January?

I think we have a much better shot the last half of January.  This December always felt like it was gonna be a yawner.  

[MossMan]

Getting a touch breezy out! 
44 degrees with .28” so far on the day. 

[Canadian guy]

43 minutes ago, Meatyorologist said:

If you asked @Phil he'd probably say yes. As for the rest of us, no idea.

I usually feel like Dewey has a pretty good perspective on how things will evolve.  

[Phil]

1 hour ago, Meatyorologist said:

If you asked @Phil he'd probably say yes. As for the rest of us, no idea.

The answer is yes.

And of course, we’ve been talking about the second half of December for awhile now (and sure enough there’s a potential snow event in the cards for some).

First part of January probably has a +PNA lean thanks to MJO transit/+EAMT, but the picture changes dramatically second half of January, especially under the condition of a major SSW w/ tropical forcing returning to constructive interference w/ Niña base state.

[AbbyJr]

6 minutes ago, Phil said:

The answer is yes.

And of course, we’ve been talking about the second half of December for awhile now (and sure enough there’s a potential snow event in the cards for some).

First part of January probably has a +PNA lean thanks to MJO transit/+EAMT, but the picture changes dramatically second half of January, especially under the condition of a major SSW w/ tropical forcing returning to constructive interference w/ Niña base state.

So you think a prolonged cold and snowy pattern is possible for the PNW during the second half of January?

[bainbridgekid]

16 minutes ago, Phil said:

The answer is yes.

And of course, we’ve been talking about the second half of December for awhile now (and sure enough there’s a potential snow event in the cards for some).

First part of January probably has a +PNA lean thanks to MJO transit/+EAMT, but the picture changes dramatically second half of January, especially under the condition of a major SSW w/ tropical forcing returning to constructive interference w/ Niña base state.

This feels a little disingenuous since your forecasts are decidedly big picture and Monday's potential event relies entirely on small scale features.

Definitely hoping the metaphorical switch can flip as we head into January though. Pacific blocking has been annoyingly absent so far this Winter.

[VancouverIslandSouth]

The 0z NAM looks a little further south with Monday's low, still a bit north of the GFS/ECMWF but it's starting to come in line with the other models:

[The Swamp]

4 minutes ago, hawkstwelve said:

Here's the 3km NAM through 9PM Monday.

This shows a fair amount more snow for the Central Sound than the 18z did.

How reliable is the NAM in the home stretch?  I doubt anyone in the gray or blue gets any sticking snow.  Tim on the other hand will likely score some sticking snow.

[Esquimalt]

5 minutes ago, hawkstwelve said:

Here's the 3km NAM through 9PM Monday.

This shows a fair amount more snow for the Central Sound than the 18z did.

Now this looks extremely similar to the december 2017 storm we've been talking about.  We need that low shifted 20 or 30 miles south for accumulation here in esquimalt.  Showing 5 or 6 inches a few miles from me but only about an inch at my place lol. 

[Phil]

20 minutes ago, bainbridgekid said:

This feels a little disingenuous since your forecasts are decidedly big picture and Monday's potential event relies entirely on small scale features.

Definitely hoping the metaphorical switch can flip as we head into January though. Pacific blocking has been annoyingly absent so far this Winter.

Not disingenuous at all. The large scale pattern is conducive for a suppressed storm track and colder than average temperatures. The mesoscale and macroscale/synoptic scale are connected at the hip.

 

[wxmet]

I could end up being wrong but I don’t think much is going to change as far as whether or not it will snow. The question is how much. Going to step out to get a few things while the 00z runs trickle in and avoid potential mass panic tomorrow.