December 2020 Weather Observations for the PNW

[MossMan]

Currently 33.3 degrees. 

[MossMan]

[BLI snowman]

BTW, November 18-19, 1897 is likely the most prominent example of a sharp anafront snowfall in the region.

People here remember November 2003 but this was basically the more badass grandpa version of that event.

Downtown Portland had a record 66/42 day on 11/18 followed by a 42/32 on 11/19 with 3" of snow. Salem went from 65/55 to 55/33 with 3" of snow and Seattle went from 61/40 to 40/34 with no measurable accumulation.

[Brian_in_Leavenworth]

14 minutes ago, bainbridgekid said:

I was thinking this may have been the first time. If it's happened though it was probably after an overrunning event that quickly transitioned to a pineapple express. Bellingham sees quicker warmups when the wind switches to SE in those setups than Seattle though.

Yeah, good point, it would be easier to happen in reverse (cold to warm).  

[MossMan]

One more pic. Have to make up for lost time now that the internet is back! This was around 6:30 when it was really coming down. Too bad the melt-a-thon has started now. 

[AbbyJr]

23 hours ago, Phil said:

SSW in La Niña/+QBO also tends to favor the West. Feb 1989 is a prolific example where the SSW was concurrent with the pattern change.

Other times there’s more of a lag. But it’s rarely denied.

So are you saying the pattern was already trending colder for the PNW without the SSW but the SSW simply made it more extreme? Or did I totally misunderstand you?

[Skagit Weather]

1 hour ago, Rubus Leucodermis said:

https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?or2709

I really haven't spent enough time looking at the historical record here. Supposedly the closest station to me (Mt Vernon 3 WNW) with a record from 1956-2005 only averaged 3.7" of snow. That seems low to me even for how terrible the snow usually is here, but if true would make it one of, if not the worst location for snow in the lowlands.

I've averaged just under 7" a year for the last 10 years which has included a number of snowless winters and a couple decent winters so 3.7" seems hard to imagine.

[jcmcgaffey]

Some crazy rainfall totals seattle north today. Several locations around lynnwood saw 4.5” of rain today.  Over 3” here in north seattle. 

[Phil]

22 minutes ago, AbbyJr said:

So are you saying the pattern was already trending colder for the PNW without the SSW but the SSW simply made it more extreme? Or did I totally misunderstand you?

That’s debatable. I’d argue in that particular case, the pattern change associated with the western cold also triggered the SSW, but there’s always a chicken egg paradox to be had.

[Ice_is_Everywhere]

Here some footage I took tonight in West Seattle.

https://www.youtube.com/watch?v=Ws9cko3ZZEk

[Phil]

Mother of all jet extensions incoming to start the new year, following Siberian High descent/+EAMT. Probably with SSW ongoing as well.

When that jet retracts and SSW completes..it gets fun.

[BLI snowman]

12 minutes ago, Skagit Weather said:

I really haven't spent enough time looking at the historical record here. Supposedly the closest station to me (Mt Vernon 3 WNW) with a record from 1956-2005 only averaged 3.7" of snow. That seems low to me even for how terrible the snow usually is here, but if true would make it one of, if not the worst location for snow in the lowlands.

I've averaged just under 7" a year for the last 10 years which has included a number of snowless winters and a couple decent winters so 3.7" seems hard to imagine.

Most of those local stations are complete garbage for snowfall data, so I wouldn't put any stock into their numbers. There's no way Mt. Vernon actually averaged 3.7" in that period.

Longterm the only really reliable stations unfortunately are the big airport sites, and even their histories have been fractured by the switch to ASOS recording in the mid 1990s.

[Deweydog]

7 minutes ago, Phil said:

Mother of all jet extensions incoming to start the new year, following Siberian High descent/+EAMT. Probably with SSW ongoing as well.

When that jet retracts and SSW completes..it gets fun.

[Deweydog]

20 minutes ago, Phil said:

That’s debatable. I’d argue in that particular case, the pattern change associated with the western cold also triggered the SSW, but there’s always a chicken egg paradox to be had.

The 1989 blast was really unique in a lot of ways.  I can’t imagine how our all star models upon models of today would have f*cked around with that for the couple weeks leading up to it.

[Jesse]

00z runs generally looked seasonably chilly the next 7-10 days. At least no awful torches like today. Good valley rains and mountain snows.

[Jesse]

Ended up with a 59/41 day here. Temperature dropped pretty quickly with the front early this evening. Picked up .40” rainfall.

[Meatyorologist]

06z GFS Init.

[Meatyorologist]

06z GFS Day 1

(Past 4 runs)

[Meatyorologist]

06z GFS Day 2

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06z GFS Day 3

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[Meatyorologist]

06z GFS Day 4

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[Meatyorologist]

06z GFS Day 5

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[Meatyorologist]

06z GFS Day 6

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[Meatyorologist]

06z GFS Day 7

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[Meatyorologist]

06z GFS Day 8

[Meatyorologist]

06z GFS Day 9

[Cloud]

To recap on 12/21/20 we had a little bit of everything. A record high day with heavy rainfall and wind — it was quite windy at one point with 20mph sustained and 30+mph gusts. Then the sun was even out for about 10 minutes while it’s raining. By 2pm or so temps was near 60! 

By about 3pm temps took a nosedive and ended up more than -20F by 5pm. The snow/sleet came for a quick 0.5” then left. At one point the flakes were as big as a quarter! Lastly, after the front passed, temps rose back up to mid 30s and a slow melt. Currently still have a dusting or so on cars and rooftops

The only thing missing on this day was an earthquake with lava flowing out from fissures. Lol

What an incredible day for our area. 

[Meatyorologist]

06z GFS Day 10

[Meatyorologist]

06z GFS 10 Day Precip/Snowfall

[Meatyorologist]

06z GFS Day 11

[Cloud]

Next 10 days or so look quite normal? Lots of 45/35 days. 

[Meatyorologist]

06z GFS Day 12

[Cloud]

Also, a lot of it was expectation for me, I didn’t expect much and was skeptical of any accumulating snowfall. Ended up enjoying the 0.5” A LOT more than anticipated. 

I think I’m going to take this approach in the future, it’s a lot more fun. And if it ended up busting, at least expectations were low. 

[Meatyorologist]

Just now, Cloud said:

Also, a lot of it was expectation for me, I didn’t expect much and was skeptical of any accumulating snowfall. Ended up enjoying the 0.5” A LOT more than anticipated. 

I think I’m going to take this approach in the future, it’s a lot more fun. And if it ended up busting, at least expectations were low. 

I took the exact same approach. Wonderful day for me.

[Meatyorologist]

06z GFS Day 13

[Meatyorologist]

06z GFS Day 14

[Meatyorologist]

06z GSF Day 15

[Meatyorologist]

06z GFS Day 16

This run went even warmer with the stratosphere.

[Chewbacca Defense]

31 this morning, I haven't ventured out this morning to see what is happening with things. When I went out to plug my car in about 10pm the snow was tapering off, and the street was a total slushfest.  Looks like we held on to everything we had last night as of when I went to bed.   I'll be curious to see how the roads are this morning.

[TT-SEA]

Temp went up overnight... even out here.    I was up at 2 a.m. and it was 38 and I checked the observations and most places were in the upper 30s.   I could hear water coming off the roof as the snow was melting.    Very disappointing.   

I didn't think it would clear out and freeze hard... but it usually does not warm up here overnight after a snowfall unless its a transition event.