Part I - January 2020 Weather Discussion for the PNW

[Front Ranger]

But it didn't. 

 

I think a lot about February 2019, to me it was something of a February version of January 1969. 

 

Point being, it all comes back to getting the right pattern. Top tier cold winter months, and temps, are still possible with the right pattern. And a little luck with snow cover, etc.

[Gradient Keeper]

I grabbed the wrong image.   I have like 150 maps saved on my desktop.   Its getting ridiculous!

 

I updated my post with the correct 00Z image after you quoted me.

 

Don't see any big changes on the EPS.   Strong signal for arctic air in western Canada and no end in sight.

I just noticed. 12z EPS today has the bitter air mass several notches closer to us. Almost entirely removed from Yukon whereas 00z last night did not. If we continue seeing that trend we'll end up very cold. I think that's what happens too.

[Front Ranger]

850mb temps never went below -5c here and I wound up with 15" of snow.

 

Pretty wacky, especially when you consider it wasn't just a Portland/Gorge event. Widespread lowland snowstorm and sub-freezing temps all the way north through the Puget Sound.

 

Must have been some really deep offshore flow and ideal low position?

[TT-SEA]

12Z EPS 10-15 day mean:

 

[Deweydog]

I think this is a classic setup where the snow chances at the lowest elevations are going to go up dramatically as you go north. I would be feeling really good about this if I was Shawnigan or someone in Bellingham. Even the Puget Sound. I think PDX and the Willamette Valley are in fine shape, but this definitely is going to be a N/S setup, not backdoor which favors Oregon. Also meaning, if there is lowland snow it is going to start a day or two sooner for folks up north, so we are going to go through the forum weenie freakout from jealous PDX weenies, who will then get their own snow the next day...

 

We also have to remember, onshore flow with -8/-9C 850mb temps is not a sure thing below 500', timing and intensity of precip would matter in that scenario.

 

I think a plausible scenario would be a decent Puget Sound snow event, a scattered 1-2" type of event south of the Columbia River, with a better chance for widespread snow PDX - south coming with some kind of shortwave associated with a 2nd push of cold air a couple days later.

 

Just throwing scenarios out there, but that is one that seems like could happen in this kind of setup.

That’s just climo. Areas north of Chehalis or so always have a better shot at significant snow in a cold onshore flow to modified Arctic air scenario.

[SilverFallsAndrew]

How do you figure not backdoor? Meaning no backdoor cold? Yakima mean temp is -10c to -12c with a lot of members to -20c. I mean it's possible it's only cold onshore flow.

 

The trough and 500mb orientation is N/S, not NE to SW like we saw with say the December 2013 blast. Doesn't mean colder air can't move down east of the Cascades or eventually offshore flow won't set up. 

[Gradient Keeper]

Wow. 12z Euro Op PNA tanks to -5 sigma, EPS to -4.5!!!! It's coming!

 

 

[SilverFallsAndrew]

That’s just climo. Areas north of Chehalis or so always have a better shot at significant snow in a cold onshore flow to modified Arctic air scenario.

 

Not rocket science, but something people tend to forget in their excitement. 

[SilverFallsAndrew]

Best EPS run yet. 

[SilverFallsAndrew]

Here were the CPC analogs for the 8-14 day period yesterday...Today's should come out soon. 

 

20020118
19520101
20020128
20070109
20080126
19740127
19520112
19750127
19890110
20020123

[BLI snowman]

Pretty wacky, especially when you consider it wasn't just a Portland/Gorge event. Widespread lowland snowstorm and sub-freezing temps all the way north through the Puget Sound.

 

Must have been some really deep offshore flow and ideal low position?

 

Classic frontongenesis along the trough axis, which just so happened to be overlayed perfectly for SW WA.

 

http://mp1.met.psu.edu/~fxg1/NARR/1998/us0111.php#picture

 

Made up for us getting dickholed the year before.

[TT-SEA]

Best EPS run yet.

A compromise will mean the ECMWF and EPS will be getting better with each run and the GFS and GEFS might back off a little.

[BLI snowman]

Wow. 12z Euro Op PNA tanks to -5 sigma, EPS to -4.5!!!! It's coming!

 

 

 

Pretty hard not to see us getting blasted in that range.

[runninthruda206]

I think we’re still headed in the right direction

[Deweydog]

Classic frontongenesis along the trough axis, which just so happened to be overlayed perfectly for SW WA.

 

http://mp1.met.psu.edu/~fxg1/NARR/1998/us0111.php#picture

 

Made up for us getting dickholed the year before.

#justice4justin

[Frontal Snowsquall]

[TigerWoodsLibido]

Let's fukkin go!!!

[Brian_in_Leavenworth]

For Western Washington, even if the arctic air only makes it to SW BC, I have seen several times where a storm system coming into WA will draw the cold air south from BC to create snow.  Dec. 1996 and March 2001 come to mind.  

[Christensen87]

Loving the darker blue 

[ShawniganLake]

I think this is a classic setup where the snow chances at the lowest elevations are going to go up dramatically as you go north. I would be feeling really good about this if I was Shawnigan or someone in Bellingham. Even the Puget Sound. I think PDX and the Willamette Valley are in fine shape, but this definitely is going to be a N/S setup, not backdoor which favors Oregon. Also meaning, if there is lowland snow it is going to start a day or two sooner for folks up north, so we are going to go through the forum weenie freakout from jealous PDX weenies, who will then get their own snow the next day...

 

We also have to remember, onshore flow with -8/-9C 850mb temps is not a sure thing below 500', timing and intensity of precip would matter in that scenario.

 

I think a plausible scenario would be a decent Puget Sound snow event, a scattered 1-2" type of event south of the Columbia River, with a better chance for widespread snow PDX - south coming with some kind of shortwave associated with a 2nd push of cold air a couple days later.

 

Just throwing scenarios out there, but that is one that seems like could happen in this kind of setup.

Yea. I’m feeling pretty good about some snow potential in the day 8-10 range up here. Probably going to be some marginal cold around that time frame with a hopefully active pattern. I’m pretty sceptical of the arctic air charging south like the gfs shows.

[BLI snowman]

#justice4justin

 

Have a feeling there'll be a downslope/dry slotting component with our upcoming snowshank redemption.

 

Sorry east county and foothills folks 

[Esquimalt]

Yea. I’m feeling pretty good about some snow potential in the day 8-10 range up here. Probably going to be some marginal cold around that time frame with a hopefully active pattern. I’m pretty sceptical of the arctic air charging south like the gfs shows.

I think your chances are very good but I’m concerned about mine here in town

[Deweydog]

Have a feeling there'll be a downslope/dry slotting component with our upcoming snowshank redemption.

 

Sorry east county and foothills folks

The coast range snow shadow is gonna f*ck us all. Sorry everybody.

[Gradient Keeper]

Even better is that long range still shows a negative mean and multiple members with -3 and -4.

Yeah without a doubt.

[ShawniganLake]

Ukmet looks interesting as early as day 6. Though it’s hard to get detailed output for that.

[Perturbed Member]

I think this is a classic setup where the snow chances at the lowest elevations are going to go up dramatically as you go north. I would be feeling really good about this if I was Shawnigan or someone in Bellingham. Even the Puget Sound. I think PDX and the Willamette Valley are in fine shape, but this definitely is going to be a N/S setup, not backdoor which favors Oregon. Also meaning, if there is lowland snow it is going to start a day or two sooner for folks up north, so we are going to go through the forum weenie freakout from jealous PDX weenies, who will then get their own snow the next day...

 

We also have to remember, onshore flow with -8/-9C 850mb temps is not a sure thing below 500', timing and intensity of precip would matter in that scenario. 

 

I think a plausible scenario would be a decent Puget Sound snow event, a scattered 1-2" type of event south of the Columbia River, with a better chance for widespread snow PDX - south coming with some kind of shortwave associated with a 2nd push of cold air a couple days later. 

 

Just throwing scenarios out there, but that is one that seems like could happen in this kind of setup. 

 

Yeah in general nothing is a slam dunk for big snow other than back door + overriding precip in the OR lowlands. The onshore stuff usually gives scattered and modest accumulations with either too much shadowing or not getting enough sustained precip to keep the temp down and actually stick. 

 

A few reasonably widespread inches of snow seem possible if you can spin up some low as the cold air spills out over the waters and have it all sink south along the coast. It just has a lot that can seem to go wrong here. I usually look to the middle of a cold spell or the transition period for some kind of event here. How often do we get a sharp arctic front here that brings the cold and the snow all in one go? Seems like basically never. It pretty much has to work as a multistep process here. 

[The Swamp]

It may be too cold to snow.

 

There may not be enough moisture for snow.

 

The cold air may just spill out over the ocean off the BC coast.

 

Things to consider.

[Gradient Keeper]

Ukmet looks interesting as early as day 6. Though it’s hard to get detailed output for that.

Oh ya?

[TigerWoodsLibido]

Yeah in general nothing is a slam dunk for big snow other than back door + overriding precip in the OR lowlands. The onshore stuff usually gives scattered and modest accumulations with either too much shadowing or not getting enough sustained precip to keep the temp down and actually stick. 

 

A few reasonably widespread inches of snow seem possible if you can spin up some low as the cold air spills out over the waters and have it all sink south along the coast. It just has a lot that can seem to go wrong here. I usually look to the middle of a cold spell or the transition period for some kind of event here. How often do we get a sharp arctic front here that brings the cold and the snow all in one go? Seems like basically never. It pretty much has to work as a multistep process here. 

 

1990 and 2008.

[MR.SNOWMIZER]

Almost time for DJ to start reading all the National Weather Service forecast discussions within 2500 miles

[ShawniganLake]

Oh ya?

Looks more amplified than anything else

[TigerWoodsLibido]

Looks more amplified than anything elseBF34746A-BDEF-4041-A830-C7F866A95BD8.gif

 

Nice low placement there if it could just hug the coast down to Cape Blanco.

[jakeinthevalley]

The coast range snow shadow is gonna f*ck us all. Sorry everybody.

How will we even know? I'm counting on the PDX radar to be down during this period.

[Gradient Keeper]

Almost time for DJ to start reading all the National Weather Service forecast discussions within 2500 miles

Ha! I've been reading the Anchorage, Juneau, and Fairbanks AFDs for the past week.

 

18z GFS in 55 minutes

[Gradient Keeper]

Looks more amplified than anything elseBF34746A-BDEF-4041-A830-C7F866A95BD8.gif

That looks real good and intriguing too with that low south of PDX. Hmmm! Definite east winds.

[MR.SNOWMIZER]

Ha! I've been reading the Anchorage, Juneau, and Fairbanks AFDs for the past week.

 

18z GFS in 55 minutes

Funny how well we all know each other on here lol.

[Gradient Keeper]

Funny how well we all know each other on here lol.

So true.

[Perturbed Member]

1990 and 2008.

 

For Dec 2008, didn't the cold air come in in the middle of the month and the big storm happened around the 21st or something? Did that low come out of the NW? My memory is kind of fuzzy on the details of that setup. 

[Gradient Keeper]

For Dec 2008, didn't the cold air come in in the middle of the month and the big storm happened around the 21st or something? Did that low come out of the NW? My memory is kind of fuzzy on the details of that setup. 

December 13th arctic front blasted southward. THEN the fun began! The 21st was the coldest day with PDX 25 F high temp.

[Deweydog]

Arctic front arrived early at the coast!

 

Dew points were already into the low 20’s in Astoria this morning.