December 2020 Weather Observations for the PNW

[bainbridgekid]

6z brings the low in just South of Seattle. Looks primed for a quick dump of heavy wet snow North and East of Seattle on this run. Slightly better than the 0z overall IMO.

 

[wxmet]

Nice shift south and it looks like Seattle is firmly placed in a PGCZ. We can handle a few more notches south

[wxmet]

Heavy snow at KSEA.

 

[TigerWoodsLibido]

[TigerWoodsLibido]

Welp, should be a whole lot of fun playing video games on Monday. I suppose football is on too.

[wxmet]

1 minute ago, bainbridgekid said:

What's the link to these?

I'd like to see KPAE.

Tropical Tidbits.

Here's KPAE:

 

[wxmet]

Pivotal Weather prints out 10 inches in Seattle with 10:1 ratio.

 

 

[Jbolin]

2 minutes ago, wxmet said:

Pivotal Weather prints out 10 inches in Seattle with 10:1 ratio.

 

 

 

Whatever falls is gonna be some of the heaviest "concrete" we've seen in recent years. 

[Gradient Keeper]

4 minutes ago, wxmet said:

Pivotal Weather prints out 10 inches in Seattle with 10:1 ratio.

 

 

That would cause a lot of tree damage and power lines.

[wxmet]

3 minutes ago, DJ Droppin said:

That would cause a lot of tree damage and power lines.

Would cripple the area. If the trends continue thru 18z I will head out to the grocery stores before they get packed.

[Gradient Keeper]

Day 5 (Past 4 runs) Greenland block trending considerably weaker. Not sure if that persists Day 6-10 though.

[wxmet]

UW-WRF 

 

 

 

[Jbolin]

1 minute ago, wxmet said:

UW-WRF 

 

 

 

A solid 8-10" from Lynnwood to Everett

Even DT area SW into W. Sea gets anywhere between 5-9"

[Gradient Keeper]

Day 7 Yeah didn't expect any real changes. Greenland block blows up. Aleutian 'ridge' is pathetic and wimpy.

 

[Jbolin]

12 minutes ago, wxmet said:

UW-WRF 

 

 

 

This map also clearly outlines what I eluded to earlier regarding strong NNW flow, YVR, the N interior, the lee of the Olympics and south sound are virtually shadowed while nearly everyone else gets hammered. 

And even the "area/s" that had nothing in earlier runs are now starting to show some color due to the new placement and shift  of the low. 

[TigerWoodsLibido]

No action on the GFS for here. Not much reason to stay up. Gonna be incredibly difficult for us folks in Oregon to focus on what might come our way one day down the pipe years from now with all the distraction of places to the north essentially being in a different climate zone at this point. A Dec-Jan event of any significance will never impact areas this far south again in our lifetimes.

[Gradient Keeper]

December 28th, 4 PM. Way out there, but precip moves into the valley with a PDX-DLS gradient of at least -8mb. Brief snow/very low snow levels turning to ice for the Gorge. Meh I dunno temps are very marginal at best.

[FroYoBro]

Going to be some nice positive temperature anomalies for Portland this weekend. Low of 50 so far today. 

[Gradient Keeper]

Water Vapor Imagery

Wow. This has geared up quickly. A long fetch of sub-tropical moisture from just northwest of Hawaii is streaming towards us. Along this there are 6 distinct areas of wave development/cyclogenesis. This weekend is going to be very wet, windy, and dynamic. Although not likely, I am not sure we can entirely rule out a wind storm due to 160kt jet support.

[SilverFallsAndrew]

Excited for the folks up north. Going to be fun to watch. Interested in how much rain we pick up in NW Oregon over the next 36-72 hours. Could be some impressive totals. End of the last couple GFS runs have been heading in the right direction. 

[Cloud]

Really fun and interesting models runs overnight. At a glance, this looks to be a bit marginal for sea level, so it might end up just being a nowcast. Worth watching models today and tonight to see how things goes but for most part, I think anyone from 800’-1000’ is in a good spot. And also typical Hood Canal special as the cold usually gets trapped there. 

[MossMan]

21 minutes ago, Cloud said:

Really fun and interesting models runs overnight. At a glance, this looks to be a bit marginal for sea level, so it might end up just being a nowcast. Worth watching models today and tonight to see how things goes but for most part, I think anyone from 800’-1000’ is in a good spot. And also typical Hood Canal special as the cold usually gets trapped there. 

I’m only at 550’...Looks like I’m out. 

[Cloud]

1 minute ago, MossMan said:

I’m only at 550’...Looks like I’m out. 

Nope! 100% not you  . Base on past performance your location is gold! So is Tim’s. 

[MossMan]

Currently 42 degrees and light rain. 
.02” so far on the day, 3.71” on the month, 57.51” on the year. 

[SilverFallsAndrew]

NAM is the snowiest run for me yet. Lol

[MossMan]

8 minutes ago, SilverFallsAndrew said:

NAM is the snowiest run for me yet. Lol

And the least for me! 

[SilverFallsAndrew]

12z might be going NORTH. 

[SilverFallsAndrew]

Looks like the low comes in about 25-30 miles north. Compared to the previous run. 

[MossMan]

NWS Seattle AFD for the “snowy” period was well...Not snowy sounding. 
 

There will be a relative lull in between weather systems on Sunday 
  with some lingering showers but nothing organized. Another wet  
  frontal system will spread rain into the area Sunday night then  
  push inland on Monday with rain changing to showers in the  
  afternoon or evening. Schneider 
   
  .LONG TERM /TUESDAY THROUGH FRIDAY/...A few showers may linger 
  into Tuesday morning, mainly over the Cascades. Otherwise, an  
  upper ridge will bring dry weather Tuesday through Thursday. A 
  front is expected to reach the area on Friday (Christmas Day) for 
  a return to wetter weather. Schneider  

[SilverFallsAndrew]

'Tim's gonna get freaking hammered regardless. There is clearly a very vigorous post frontal convergence zone shown on the models. 

[MossMan]

6 minutes ago, SilverFallsAndrew said:

'Tim's gonna get freaking hammered regardless. There is clearly a very vigorous post frontal convergence zone shown on the models. 

Hope he has his snowblower tuned up and ready to roll...

[SilverFallsAndrew]

Looking like about 4-6" of precip at my place over the next 72 hours. Would get us up to and perhaps even slightly above average for the month. 

[Cloud]

7 minutes ago, MossMan said:

NWS Seattle AFD for the “snowy” period was well...Not snowy sounding. 
 

There will be a relative lull in between weather systems on Sunday 
  with some lingering showers but nothing organized. Another wet  
  frontal system will spread rain into the area Sunday night then  
  push inland on Monday with rain changing to showers in the  
  afternoon or evening. Schneider 
   
  .LONG TERM /TUESDAY THROUGH FRIDAY/...A few showers may linger 
  into Tuesday morning, mainly over the Cascades. Otherwise, an  
  upper ridge will bring dry weather Tuesday through Thursday. A 
  front is expected to reach the area on Friday (Christmas Day) for 
  a return to wetter weather. Schneider  

The NWS in this region have gone full on nowcast the last few years. Super conservative and maybe rightfully so.

[SilverFallsAndrew]

Just now, MossMan said:

Hope he has his snowblower tuned up and ready to roll...

He could easily see a foot. Down here I think best cast scenario is 3-4", most likely no more than 1-2" of slop. 

[SilverFallsAndrew]

Some areas of the Northern Oregon Cascades and Coast range could see up to 8" of precip in the next 72 hours. Some potential for landslides and debris flows in the burn scars. Likely many of the smaller streams and coastal rivers will flood. 

[Front Ranger]

8 hours ago, MossMan said:

I hope you all realize that our extreme weenieism (is that a word?) this morning caused the model shift...Way to go team weenies!!! 

I think Andrew writing off December altogether was the turning point.

[MossMan]

3 minutes ago, SilverFallsAndrew said:

He could easily see a foot. Down here I think best cast scenario is 3-4", most likely no more than 1-2" of slop. 

I’m thinking an inch or so of slop here...But will be pleasantly surprised by anything really. A little slop or 6”...I will take it in this positive PNA state right now. 

[MossMan]

4 minutes ago, hawkstwelve said:

12z GFS cut back slightly on totals.

Still not bad for foothills areas.

 

 

I’m in the 5th shade of blue...I’ll take it! 

[Dave]

Sorry guys. It ain't happening.

[Cloud]

7 minutes ago, hawkstwelve said:

12z GFS cut back slightly on totals.

Still not bad for foothills areas.

 

 

Clear PSCZ signature for the N. Sound. Someone usually scores really well inside that triangle.