December 2023 Weather in the PNW

[Anti Marine Layer]

1 hour ago, Phil said:

Can see this process extraordinary well on the 00z EPS.

- Troughing develops over Siberia, which due to presence of Himalayas/terrain, acts to remove momentum from the NPAC jet, culminating in a series of wavebreaks/meridional flow over the NPAC D5-10

- At the same time, the anticyclone in the Beaufort/western Arctic couples with the stratospheric high/wave-1 (associated with the stratwarm). This process acts to drop NAM/AO. 

- Zonal flow in Canada quickly becomes meridional, dipping the jet in W-Canada and instigating another large wavebreak over NE-Canada/Greenland, culminating in a substantial -NAO that keeps the northern jet suppressed.

Big wrinkle here the in-situ blowtorch airmass in W-Canada, which precludes a rapid buildup of arctic air there (which tends to happen more slowly than modeled anyway). This is despite a seemingly ideal 500mb progression. If it wasn’t so warm up there to start with, this pattern progression (as modeled) would easily have driven arctic air into SW-Canada & W-US. But that is going to be a challenge in this situation. It can be overcome if the pattern holds long enough, though.

Makes me dizzy 

[Slushy Inch]

Chances for 32 or lower high no longer zero on 8th.

[SilverFallsAndrew]

Just now, Rubus Leucodermis said:

Chilly, but not really cold next weekend.

No, it's definitely below average though. It's not really that impressive of an airmass, but it would cool over time if we can get some low level cold established. 

[snow_wizard]

3 minutes ago, Rubus Leucodermis said:

Chilly, but not really cold next weekend. Though it will probably feel cold in relation to all the first rate quality torching we have been experiencing.

This sounds kind of negative compared to what might be brewing for us.

BTW...the 6z ECMWF shows SEA with a chilly start to January with 44/30.

[SilverFallsAndrew]

Just now, snow_wizard said:

This sounds kind of negative compared to what might be brewing for us.

BTW...the 6z ECMWF shows SEA with a chilly start to January with 44/30.

It's about perspective too. Our expectations for this winter are in the basement and so far 95% of us have seen nothing. There were probably a dozen colder troughs last winter, but just having something nice will be fun. Also having it happen in January is always a +. 

[Rubus Leucodermis]

4 minutes ago, snow_wizard said:

This sounds kind of negative compared to what might be brewing for us.

BTW...the 6z ECMWF shows SEA with a chilly start to January with 44/30.

The stuff that “might be brewing” is in deep clown range (over a week out). Really just a vague possibility of something interesting at this point. I prefer not to speculate much on it until the time frame gets closer and the picture gets clearer.

A week out is still clown rangey as well, so the rug may get pulled on that chilliness and it may be more 50-burgers. Or perhaps a surprise freeze. Who knows. But at this stage next weekend appears to be chilly but not cold.

[snow_wizard]

This would be a bona fide miracle for January in this century!  Keep in mind the meteograms are notoriously warm for mins at SEA as well.

[snow_wizard]

The second shot is looking better on the GEFS this run.  More really cold members are giving the mean a nicer look.  There is potential for this to go full blown cold for us.  Still too soon to tell.

[Deweydog]

I think Jim is ON BOARD.

[Skagit Weather]

20 minutes ago, Rubus Leucodermis said:

Chilly, but not really cold next weekend. Though it will probably feel cold in relation to all the first rate quality torching we have been experiencing.

Anything is better than what we've been seeing. In the last 4 days I've only spent 2 hours below 50F. This December will end up warmer than most of the Marches I've seen in the last decade.

[SilverFallsAndrew]

8 hours ago, Gradient Keeper said:

00z CMCE Day 8-14 Analog Composite.
Yeah. This will do nicely. If only this pattern were to play out.

I'm often critical of these composites, but for a fun exercise I decided to look at how these events panned out, that are on this list. I just did the day of as listed above and then went out a week. Interesting. These #'s are for SLE. Most were pretty good outcomes, some completely failed. The 1962 stretch is interesting, the 7th day was the first day of an extended arctic BLAST. 

1971:

7      41     32   36.5   -5.0     28      0   0.02    0.0      0
 8      47     41   44.0    2.5     21      0   0.39    0.0      0
 9      50     44   47.0    5.4     18      0   0.12    0.0      0
10      45     35   40.0   -1.7     25      0   0.56      T      0
11      36     31   33.5   -8.3     31      0   0.27    1.0      0
12      33     29   31.0  -10.9     34      0   0.23    4.0      2
13      34     25   29.5  -12.5     35      0   0.26    5.3      3

1968:

 3      46     28   37.0   -4.1     28      0      T    0.0      0
 4      36     27   31.5   -9.7     33      0   0.00    0.0      0
 5      47     28   37.5   -3.8     27      0      T    0.0      0
 6      36     26   31.0  -10.4     34      0   0.00    0.0      0
 7      45     29   37.0   -4.5     28      0   0.14    0.0      0
 8      47     35   41.0   -0.5     24      0   0.25    0.0      0
 9      50     36   43.0    1.4     22      0   1.24    0.0      0

2004:

Day   MaxT   MinT   AvgT   Dprt    HDD    CDD   Pcpn   Snow   Dpth
 1      37     30   33.5   -7.5     31      0   0.26      M      M
 2      37     33   35.0   -6.1     30      0   0.14      M      M
 3      38     33   35.5   -5.6     29      0   0.10      M      M
 4      37     24   30.5  -10.7     34      0   0.13      M      M
 5      24     19   21.5  -19.8     43      0   0.01      M      M
 6      29     19   24.0  -17.4     41      0   0.61      M      3
 7      32     28   30.0  -11.5     35      0   0.55      M      M

1976:

3      45     36   40.5   -0.6     24      0   0.21    0.0      0
 4      49     42   45.5    4.3     19      0   0.71    0.0      0
 5      48     37   42.5    1.2     22      0   0.24    0.0      0
 6      44     33   38.5   -2.9     26      0   0.32    0.0      0
 7      51     38   44.5    3.0     20      0   1.19    0.0      0
 8      51     40   45.5    4.0     19      0   0.11    0.0      0
 9      46     35   40.5   -1.1     24      0      T    0.0      0

1988:

25      38     27   32.5   -8.2     32      0   0.00    0.0      0
26      41     26   33.5   -7.2     31      0   0.00    0.0      0
27      42     33   37.5   -3.2     27      0   0.01    0.0      0
28      40     30   35.0   -5.8     30      0      T      T      0
29      49     39   44.0    3.2     21      0   0.09    0.0      0
30      49     39   44.0    3.1     21      0   1.05    0.0      0
31      47     36   41.5    0.6     23      0      T    0.0      0

1981:

26      43     35   39.0   -1.7     26      0   0.62    0.0      0
27      43     36   39.5   -1.2     25      0   0.54    0.0      0
28      46     29   37.5   -3.3     27      0   0.20    0.0      0
29      39     25   32.0   -8.8     33      0   0.00    0.0      0
30      42     25   33.5   -7.4     31      0   0.00    0.0      0
31      40     30   35.0   -5.9     30      0   0.37      T      T

1st            41           33 

1996:

27      37     33   35.0   -7.8     30      0   0.63    0.0      0
28      43     35   39.0   -3.8     26      0   0.14    0.0      0
29      40     23   31.5  -11.4     33      0      T    0.0      0
30      32     19   25.5  -17.4     39      0   0.00    0.0      0
31      34     19   26.5  -16.5     38      0   0.00    0.0      0

1                35           17      26.0       -17.0

2                35           15      25.0       -18.1

1982:

20      44     31   37.5   -4.9     27      0   0.00    0.0      0
21      42     33   37.5   -5.0     27      0   0.00    0.0      0
22      47     35   41.0   -1.6     24      0   0.97    0.0      0
23      54     47   50.5    7.9     14      0   1.04    0.0      0
24      51     41   46.0    3.3     19      0   0.53    0.0      0
25      54     40   47.0    4.3     18      0   0.14    0.0      0
26      47     41   44.0    1.2     21      0   0.16    0.0      0

1959:

 1      47     36   41.5    0.5     23      0   0.08    0.0      0
 2      38     22   30.0  -11.1     35      0      T      T      0
 3      29     17   23.0  -18.1     42      0   0.00    0.0      0
 4      26     17   21.5  -19.7     43      0   0.31    3.0      0
 5      30     23   26.5  -14.8     38      0   0.40    0.4      2
 6      40     17   28.5  -12.9     36      0   0.02    0.0      2
 7      52     35   43.5    2.0     21      0   0.71    0.0      1

1962:

13      44     31   37.5   -4.5     27      0   0.00    0.0      0
14      42     31   36.5   -5.5     28      0   0.07    0.0      0
15      46     31   38.5   -3.6     26      0      T    0.0      0
16      44     29   36.5   -5.7     28      0   0.02    0.0      0
17      41     35   38.0   -4.3     27      0   0.09    0.0      0
18      38     29   33.5   -8.8     31      0   0.13    0.1      0
19      29     20   24.5  -17.9     40      0   0.06    2.4      0

 

[Phishy Wx]

7 minutes ago, Deweydog said:

I think Jim is ON BOARD.

oof

[AlTahoe]

47 minutes ago, Phil said:

You’ve had some bad luck w/rt disconjunction of subseasonal forcings for jet extension into CA and the low frequency state. Continued piss-poor rolls of the dice.

The coming -NAM/-NAO significantly improves the low frequency signal there, so assuming it holds through mid/late winter (which it usually does in El Niño winters) the next +dAAMt/jet extension is much more likely to deliver significant snowfall to CA mountains (and overall precipitation to the SW US).

I don’t know what seasonality of niño precipitation is out there in CA (or how it has changed in recent events?) but I think a lot of people misunderstand the true nature of niño climo. People associate El Niño with heavy rains (and mountain snows) in California and big east coast snowstorms, but much of that is exclusively a late winter phenomenon, with a middling, rudderless pattern typically dominating during the first half of winter.

(Graphic from Eric Webb on Twitter/X) Something that might surprise people is that moderate/strong *La Niña* climatology is more favorable for significant snowstorms out here until January 27th, when the switch flips. You’d never know this reading most weather forums, though.  https://x.com/webberweather/status/1741115005158707415?s=46&t=656Z973wLtGKaIyhhq_7QQ

The only strong El ninos this dry went on to be disaster years. Usually the storm track starts off early in Nov and continues through winter with a big uptick Feb onward. If it hasn't happened by this point it ain't gonna happen according to all of the other El Nino seasons. 

[SilverFallsAndrew]

Just now, AlTahoe said:

The only strong El ninos this dry went on to be disaster years. Usually the storm track starts off early in Nov and continues through winter with a big uptick Feb onward. If it hasn't happened by this point it ain't gonna happen according to all of the other El Nino seasons. 

Which ones failed in this manner? 

[SilverFallsAndrew]

Massive ensemble improvement in the long range. 

[ShawniganLake]

4 hours ago, TT-SEA said:

06Z GFS shows a significant snow event for the Seattle area within a week... this happens next Friday which is just 6 days away now.

 

Hmm. We’ve seen that odd band of snow through the Puget sound on the GFS before when temps are too warm.  Overall a pretty good 12Z run though. 

[SnowWillarrive]

48 minutes ago, snow_wizard said:

This would be a bona fide miracle for January in this century!  Keep in mind the meteograms are notoriously warm for mins at SEA as well.

Greatest January since 1950 about to commence 

[the_convergence_zone]

9.80” of rain on the month now. Still a slight chance of getting to 10”. 

[TT-SEA]

6 minutes ago, ShawniganLake said:

Hmm. We’ve seen that odd band of snow through the Puget sound on the GFS before when temps are too warm.  Overall a pretty good 12Z run though. 

Might be a moot point for Friday... 12Z ECMWF shows heavy rain and a strong SW wind that day.

[Slushy Inch]

Like Andrew said. Ensemble improvement in long range too.

[ShawniganLake]

58 minutes ago, snow_wizard said:

This would be a bona fide miracle for January in this century!  Keep in mind the meteograms are notoriously warm for mins at SEA as well.

I think you’re actually selling January short.  We’ve seen better stuff than that in January this century. 

[Slushy Inch]

Trends continue 

[TT-SEA]

4 minutes ago, ShawniganLake said:

I think you’re actually selling January short.  We’ve seen better stuff than that in January this century. 

January 2012 and 2020 come to mind right away for my area.   Lots of snow with cold temps here.

[ShawniganLake]

11 minutes ago, TT-SEA said:

Might be a moot point for Friday... 12Z ECMWF shows heavy rain and a strong SW wind that day.

FWIW the ICON has shown a potent storm crossing the PNW next weekend. Moderate windstorm potential 

[Deweydog]

Sunbreak!!

[SilverFallsAndrew]

Just now, Slushy Inch said:

Like Andrew said. Ensemble improvement in long range too.

It really doesn't get much better than this...

[ShawniganLake]

1 minute ago, TT-SEA said:

January 2012 and 2020 come to mind right away for my area.   Lots of snow with cold temps here.

Not to mention 2017. Despite the lack of snow some areas it was consistently cold and of course Portland got nuked. 

[TT-SEA]

1 minute ago, ShawniganLake said:

Not to mention 2017. Despite the lack of snow some areas it was consistently cold and of course Portland got nuked. 

2012, 2017, 2020... makes sense that 2024 would be next.  

[TT-SEA]

12Z ECMWF shows a little snow next Sunday.

[ShawniganLake]

GEFS has a few members go arctic.  GEPS not so Much.   I have noticed the Canadian ensemble doesnt seem to go crazy cold in the long range as easily as the GEFS does. 
 

 

[TigerWoodsLibido]

3 minutes ago, TT-SEA said:

12Z ECMWF shows a little snow next Sunday.

Would that be a late Dec 2021 situation with some heavy showers rolling in and some onshore flow snow?

[SilverFallsAndrew]

I'd say January has been better further north. It's been a disaster down here since 2017, other than some cold weather for a couple days last January and we had a good snow event in 2020, but that cut off at about 1200'. 

For NW Oregon I'd rank the Januaries this century as follows. 

1) 2017 - Not even close. Some isolated spots in the valley saw snow squalls the evening of New Year's Day, then several days of very cold weather with lows well into the teens. An overrunning event on the 7/7th that brought 2-5" of snow from PDX to Eugene and freezing rain. Then the big snow event for PDX on the 11th, which was followed by a week of very cold weather, even further down the valley where snow did not fall on the 11th. The south valley also got snow on the 4th from the system that pounded Medford with record snow. 

2) 2004 - Arguments could probably be made for other years here, but this was by far the biggest January arctic blast of the 21st Century. Significant snow event on New Year's Day and then classic snow/ice storm a few days later. Coldest high temp this Century for SLE of 24. 2nd biggest icing event this Century behind February 2021. 

3) 2007 - Chilly month, modified arctic air for about a week. Some decent low elevation snows. 

4) 2008 - Underrated for how chilly it was. Incredible foothill snows and a significant south valley snow event. 

5) 2013 - Almost entirely inversion based  but one of the coldest Januaries this century and multiple sub-freezing highs. 

 

After writing this list I have to say, this is a pathetic list... 

 

[TigerWoodsLibido]

Some dawgs in there.

[TT-SEA]

4 minutes ago, TigerWoodsLibido said:

Would that be a late Dec 2021 situation with some heavy showers rolling in and some onshore flow snow?

No... that was intense snow with an arctic boundary.    This looks some snow and ice pellet showers with temps in the upper 30s.

[ShawniganLake]

8 minutes ago, TT-SEA said:

2012, 2017, 2020... makes sense that 2024 would be next.  

January 2004, 2005, and 2007 come to my mind as well

[Andstorm]

Favorable pattern vs strong El Niño…let the games begin. 

[TT-SEA]

Total snow per 12Z ECMWF.

[TigerWoodsLibido]

At least some cooler temps and foothill snow would be nice.

[SilverFallsAndrew]

Just now, TigerWoodsLibido said:

At least some cooler temps and foothill snow would be nice.

At face value what we are seeing in the models is nothing to write home about. But it is better than what we have seen and has the potential to trend better. 

[TT-SEA]

7 minutes ago, TigerWoodsLibido said:

At least some cooler temps and foothill snow would be nice.

Mountain snow would be wonderful.