December 2020 Weather Observations for the PNW

[snow_wizard]

The EPS is certainly better than the 12z was.  Interestingly it has lower heights over the NW during week 2 in spite of a stronger -NAO signal.

[snow_wizard]

1 hour ago, Phil said:

It can, and often does. However, the exact time of year and in-situ tropical low pass regime often matters just as much, sometimes more.

Once the event gets closer, it’s easier to extrapolate some of the elements. But the SSW itself can also reshuffle the low pass tropical forcing, ignite the MJO, etc.

IIRC, in 1987/88, a SSW torpedoed El Niño in its tracks by setting off one of the stronger MJO events of the decade into destructive interference at a vulnerable point in the OKW cycle. I’m not 100% sure if that’s the correct year but that is the sum of it.

 

I do know that we had a really close call with something epic in early Feb 1988.  As it is it got cold here with a little bit of snow in late Jan / early Feb.  Rare for a Nino.

[snow_wizard]

1 hour ago, Phil said:

ECMWF vs GFS D10.

Notice how GFS wants to finish with a much stronger Eurasian daughter vortex vs the ECMWF...which is both more aggressive with the event and sooner to split it vs GFS.

How exactly that unfolds could, in theory, make a difference. One of the many “dominoes” @Brian_in_Leavenworth mentioned.

This is going to be a fun learning experience for all of us.  It's pretty easy to see this is going to have an impact on the remainder of this winter.

[snow_wizard]

The GFS meteograms show two decent cold snaps over the next two weeks.  The first Sunday night through Tuesday (maybe into Wednesday) and the other around January 5.  The early January one shows two high temps below 40 for SEA.

[Jesse]

Raw and chilly Christmas, 39/34 spread here with close to 1/2” of rain. Snow was close to mixing in at points during the onset of precip.

Currently light rain and 38. ESE winds are still hanging on for now although I see many spots have switched to southerlies this evening. Should break through here by morning.

[GHweatherChris]

Next?

[TigerWoodsLibido]

50/34 on Christmas for a positive temp departure...same old same old benign weather...

We are putting a dent in the drought conditions down here though so that's very good.

[El_Nina]

45 and raining, 0.15" past 4 hours. Up and over 9" for December at 9.16." Glad we had proper weather for Christmas this year, was getting a little worried seeing the big ridge parked over us about a week ago. 

[Gradient Keeper]

 

6z GFS .... Through Day 13. It could be nothing, but after Day 6 Day this run does not have a Greenland block with the positive anomaly displaced further south over Maine, Newfoundland, the Labrador Sea, and North Atlantic. This is the first GFS Op run in many days that did not feature persistent ridging/blocking over NE Canada and Greenland. Am I just grasping at straws? Maybe.

[SilverFallsAndrew]

I feel like the last few model runs have been even worse.

[Cloud]

After a few days of legit chilliness weather, we’re back to this sh*t  on a late Dec. morning.  Yuck

 

[Timmy Supercell]

Maybe 1/20th inch outside. Still not quite measurable but its enough to make everything white.

Off and on moderate snow rates but some of these showers are small and move through quickly.

[Timmy Supercell]

1 hour ago, SilverFallsAndrew said:

I feel like the last few model runs have been even worse.

The 12/29-30 snow was taken away again, still shows a moderate amount from Jan 2-4. I wouldn't write home about it though.

[TacomaWaWx]

Got down to 44 this morning...0.01” so far. 

[TT-SEA]

46 degrees here with a strong south wind... snow is just about gone.

 

 

 

Edited December 26, 2020 by TT-SEA

[TT-SEA]

Luckily Snoqualmie Pass avoided the warm up... only 26 there.

 

[Brian_in_Leavenworth]

5 inches of new snow yesterday afternoon and evening.  This snow will stick around and begin to pile up starting later this week.

[BLI snowman]

4 hours ago, SilverFallsAndrew said:

I feel like the last few model runs have been even worse.

Yeah, 06z OP was a flaming pile of doorstep dung. Cut way back on precip and general action but still kept the progressive theme going until further notice. Didn't bother to check the ensembles due to my utter despondence. 

[Rubus Leucodermis]

Got as warm as 50˚F in last night's southerlies. Now 46˚F. Except for a few lingering piles, snow is gone.

[Timmy Supercell]

Just a thin 1/10" layer of white this morning. Total yesterday was a Trace. Goes to show you not to expect snow on Christmas west of the cascades if it happens less than 50% of the time east of the Cascades.

[Skagit Weather]

Quite windy out there last night. Gusted to 35mph here which is one of the strongest storms of the season. Hit 50F again which now put my average high for the month at 49F. Of course that will drop in the next few days, but will still make this one of my warmest Decembers I've recorded.

[Rubus Leucodermis]

1 minute ago, Timmy_Supercell said:

Just a thin 1/10" layer of white this morning. Total yesterday was a Trace. Goes to show you not to expect snow on Christmas west of the cascades if it happens less than 50% of the time east of the Cascades.

Just had a white Christmas yesterday (assuming existing snow on the ground counts). That makes four of them that I’ve experienced west of the Cascades since 2000 (other years were 2017, 2008, and 2007). I don’t think that’s doing too badly, but that's still an 80% chance of having a green Christmas.

[Timmy Supercell]

4 minutes ago, Rubus Leucodermis said:

Just had a white Christmas yesterday (assuming existing snow on the ground counts). That makes four of them that I’ve experienced west of the Cascades since 2000 (other years were 2017, 2008, and 2007). I don’t think that’s doing too badly, but that's still an 80% chance of having a green Christmas.

I was also comparing Portland's history of white Christmases, which are way more rare than that. Think their last one was 2008, and that was the only time I remember one when I lived in NW Oregon. A post NWS Medford did last year saying MFR runs about a 2% chance of a white Xmas any given year, probably means PDX runs 1%. lol

[Rubus Leucodermis]

12 minutes ago, Timmy_Supercell said:

I was also comparing Portland's history of white Christmases, which are way more rare than that. Think their last one was 2008, and that was the only time I remember one when I lived in NW Oregon. A post NWS Medford did last year saying MFR runs about a 2% chance of a white Xmas any given year, probably means PDX runs 1%. lol

PDX actually had Christmas Day flurries in 2007. Seattle had some brief accumulations, but I was in PDX at the time.  PDX did get Christmas snow in 2017, too. And of course 2008 was an epically white Christmas. Still, 3 out of 20 is not exactly favorable odds, and that’s probably the most favorable 20-year period on record.

Update: I think in PDX it was just snow on the ground from a snowfall on the previous day in 2017. Still, if snow on the ground counts, it counts.

[Timmy Supercell]

4 minutes ago, Rubus Leucodermis said:

PDX actually had Christmas Day flurries in 2007. Seattle had some brief accumulations, but I was in PDX at the time.  PDX did get Christmas snow in 2017, too. And of course 2008 was an epically white Christmas. Still, 3 out of 20 is not exactly favorable odds, and that’s probably the most favorable 20-year period on record.

I remember 2007. NWS is pretty nitpicky when it comes to their definition of one. Has to accumulate, and be 1".

Maybe they should loosen up standards for cities that only see maybe a few days window of snow annually.

[BLI snowman]

14 minutes ago, Timmy_Supercell said:

I was also comparing Portland's history of white Christmases, which are way more rare than that. Think their last one was 2008, and that was the only time I remember one when I lived in NW Oregon. A post NWS Medford did last year saying MFR runs about a 2% chance of a white Xmas any given year, probably means PDX runs 1%. lol

Portland had a white Christmas in 2017 with 1" on the ground.

2007 also counts with a trace of snow at PDX and a sloppy dusting for most of the metro area above 100'.

[TigerWoodsLibido]

PDX had a White Christmas in 2017. The place that’s most due is EUG which hasn’t had one since 1990.

[BLI snowman]

10 minutes ago, Rubus Leucodermis said:

PDX actually had Christmas Day flurries in 2007. Seattle had some brief accumulations, but I was in PDX at the time.  PDX did get Christmas snow in 2017, too. And of course 2008 was an epically white Christmas. Still, 3 out of 20 is not exactly favorable odds, and that’s probably the most favorable 20-year period on record.

Update: I think in PDX it was just snow on the ground from a snowfall on the previous day in 2017. Still, if snow on the ground counts, it counts.

Yeah, the snow was on 12/24 in 2017.

And you're right, we've actually been pretty fortunate the last 15 years with Christmas snow. 3 instances in that timeframe, including the massive event in 2008, is good by historic standards and means we're likely set for a little while.

Before that you have to go back to 1990, which had an inch on the ground, and 1983, which had a dusting. There was a trace in 1965 and a widespread light event in 1954, and then that's it for the PDX era. The 19th century was obviously a lot better but that kind of goes without saying.

[TigerWoodsLibido]

Just now, BLI snowman said:

Yeah, the snow was on 12/24 in 2017.

And you're right, we've actually been pretty fortunate the last 15 years with Christmas snow. 3 instances in that timeframe, including the massive event in 2008, is good by historic standards and means we're likely set for a little while.

Before that you have to go back to 1990, which had an inch on the ground, and 1983, which had a dusting. There was a trace in 1965, a widespread light event in 1954, and that's it for the PDX era. The 19th century was obviously a lot better but that kind of goes without saying.

Nothing from the 19th century until the 1950s? That’s depressing and makes it seem more likely that we will go longer than a century here before another one.

[TheNewCulverJosh]

2 minutes ago, BLI snowman said:

Yeah, the snow was on 12/24 in 2017.

And you're right, we've actually been pretty fortunate the last 15 years with Christmas snow. 3 instances in that timeframe, including the massive event in 2008, is good by historic standards and means we're likely set for a little while.

Before that you have to go back to 1990, which had an inch on the ground, and 1983, which had a dusting. There was a trace in 1965, a widespread light event in 1954, and that's it for the PDX era. The 19th century was obviously a lot better but that kind of goes without saying.

Yes, the snow in 2017 was on Christmas eve.  I remember it vividly in Happy Valley, started out as some sprinkles then got heavier and turned into a nice coating if ice mainly on cars and sidewalks, then a very quick hitting line of all snow rolled through after dark, snowed gangbusters for a good hour or two, then that was it.  I believe it got into the mid 40s Christmas day.

[SilverFallsAndrew]

Good lord the models are in the wilderness right now. We can write off the first half of January at this point. 

[TT-SEA]

3 years ago this morning... 12/26/17.

[Blizzard777]

1 hour ago, TT-SEA said:

Luckily Snoqualmie Pass avoided the warm up... only 26 there.

 

Leavenworth got into the swing of things Christmas evening with snow falling. 

27*  there currently and winter wonderland once again. 

[Brian_in_Leavenworth]

 

 

MJVentrice

@MJVentrice·

4h

Nearly all ECMWF Monthly model ensemble members reversal 10mb zonal winds during early January. This illustrates a significant sudden stratospheric warming event will be at hand. Still waiting to see if the Stratospheric Polar Vortex splits or not, but there's a good chance here.

 

Judah Cohen

@judah47

Dec 25

Not sure I can ever recall a pattern like this across the Northern Hemisphere - all wave one (almost looks like +AO but with the polar low over Bering Sea). Should bang on the #polarvortex pretty good; cold, stormy with mountain #snow in western N America & mild in the East.

 

Judah Cohen

@judah47

21h

Some impressive WAFz (poleward heat transport in the atmosphere that perturbs the #polarvortex) predicted by GFS over the next two weeks. As I have been writing in the blog, it is my observation that when the WAFz is that strong it is mild in the Eastern US.

 

[Timmy Supercell]

3 minutes ago, TT-SEA said:

3 years ago this morning... 12/26/17.

Looks like you guys had a lot more snow than I did. Only thing I got was a hard freeze 12/26/2017.

 

[SilverFallsAndrew]

Just now, Brian_in_Leavenworth said:

 

 

MJVentrice

@MJVentrice·

4h

Nearly all ECMWF Monthly model ensemble members reversal 10mb zonal winds during early January. This illustrates a significant sudden stratospheric warming event will be at hand. Still waiting to see if the Stratospheric Polar Vortex splits or not, but there's a good chance here.

 

Judah Cohen

@judah47

Dec 25

Not sure I can ever recall a pattern like this across the Northern Hemisphere - all wave one (almost looks like +AO but with the polar low over Bering Sea). Should bang on the #polarvortex pretty good; cold, stormy with mountain #snow in western N America & mild in the East.

 

Judah Cohen

@judah47

21h

Some impressive WAFz (poleward heat transport in the atmosphere that perturbs the #polarvortex) predicted by GFS over the next two weeks. As I have been writing in the blog, it is my observation that when the WAFz is that strong it is mild in the Eastern US.

 

Hmmmm

[BLI snowman]

13 minutes ago, TigerWoodsLibido said:

Nothing from the 19th century until the 1950s? That’s depressing and makes it seem more likely that we will go longer than a century here before another one.

No, Portland had white Christmases in 1937, 1924, 1921, and 1909. Just wasn't measured at PDX since it didn't exist yet 

[Brian_in_Leavenworth]

2 minutes ago, Jginmartini said:

Leavenworth got into the swing of things Christmas evening with snow falling. 

27*  there currently and winter wonderland once again. 

Yup.  We had 5 inchesl yesterday afternoon and evening.  This snow will stick around, as the polar jet will eventually head our way and give a lot more snow to our area.  Last year it seems we got the southern jet and the systems were warm.  So it won't be bitter cold, but seasonal temps will give us lots of snow.

[MR.SNOWMIZER]

6 minutes ago, SilverFallsAndrew said:

Good lord the models are in the wilderness right now. We can write off the first half of January at this point. 

We will be chasing our tale like every year and then its March.  

[TT-SEA]

Feels sort of spring-like out there this morning...