January 2024 Weather in the PNW (Part II)

[NorthBend RainEnthusiast]

2 minutes ago, Cloud said:

What are the D and E For the euro? 

Deterministic and Ensemble

Full acronym list: https://www.weather.gov/media/mdl/nbm/v3.1_Model_Inputs.pdf

[Front Ranger]

14 minutes ago, Brian_in_Leavenworth said:

From what I've read, the NBM isn't simply taking every ensemble run and making a mean out of all of them. Nor does it "favor" one model over another or weigh one model over another.

It sounds like it weighs all of them, but instead of a simple mean, it takes into account all known biases and tendencies of each model and then blends it all in.

And over time it has improved, partly because models have improved, and partly because it better understands model tendencies and biases and better takes them into account 

 

Makes sense. I'd imagine skill level goes down significantly with particularly complex and less sampled situations like this but who knows. 

[RCola]

5 minutes ago, Parrot said:

I'm no expert but as far as I was aware, arctic front events range from very marginal to localized at best. And the models are only calling for a trace with the front. Getting snow going into an event is not necessarily an event caused by the arctic front. But please corect me if I'm a bit off base...

Sounds right with what I know. Someone will get more than a trace from the front, with climatologically favored areas more likely to receive a few inches.

I'm confident we get mood flakes in Seattle. Anything extra is gravy, and my weenie self will jump for joy.

[Mid Valley Duck]

17 minutes ago, Brian_in_Leavenworth said:

From what I've read, the NBM isn't simply taking every ensemble run and making a mean out of all of them. Nor does it "favor" one model over another or weigh one model over another.

It sounds like it weighs all of them, but instead of a simple mean, it takes into account all known biases and tendencies of each model and then blends it all in.

And over time it has improved, partly because models have improved, and partly because it better understands model tendencies and biases and better takes them into account 

 

I've heard from a NWS employee who shall remain anonymous, that while it is a great tool they are basically forced to forecast off of it. So situations like last February for Portland completely bust because they can't use their human touch on their official forecasts.

[Front Ranger]

14 minutes ago, iFred said:

The bias accounted for are very very very very simplified. The usefulness though is that because the heavy lifting is moved to other models, it had the best (re: safest) "modeled" terrain influences. I remember coming across a paper when the HRRR came out stating that some NWS offices were using the NBM for nowcasting.

So basically it's most effective in the very short term?

[TigerWoodsLibido]

I feel like the cutoff line for snow during the critical period will stall out somewhere around Tangent or Brownsville.

[MR.SNOWMIZER]

Bold but possible prediction. 

Somewhere between Salem and Tacoma will get 18 inches of snow this weekend. Should be a wide area of 6-12.

If a landfall happens around Astoria the hood canal area could see 18-30 inches.

Edited January 9 by MR.SNOWMIZER

[Frontal Snowsquall]

24 minutes ago, Perturbed Member said:

18z GRAF. Looks like it sobered up. Doesn't matter too much though, I think we have a pretty decent idea of the range of possibilities tonight. 

We’re starting to get in the range now where we can track the cold air later this week with the GRAF. The 12z has SEA get to freezing around Thursday midnight. The 18z has PDX just start to develop an east wind on Friday 10am with temps dropping.

[iFred]

View from work. Lake Union looking north.

[TT-SEA]

Total snow overnight per 18Z ECMWF... about half of what the GFS shows.    We need about 6 inches in downtown Portland tonight to trust the GFS snow amounts.

[LowerGarfield]

NWS Spokane puts me under a WWA from 1am-4pm tomorrow and 1am Thur-4pm Fri. I personally think they are jumping the gun for WSW since the Euro and GFS widely disagree. Surprised about WWA but not as much since it's tonight.

URGENT - WINTER WEATHER MESSAGE
National Weather Service Spokane WA
244 PM PST Tue Jan 9 2024


...WINTER WEATHER ADVISORY IN EFFECT FROM 1 AM TO 4 PM PST
WEDNESDAY...
...WINTER STORM WATCH IN EFFECT FROM LATE WEDNESDAY NIGHT THROUGH
FRIDAY AFTERNOON...

* WHAT...For the Winter Weather Advisory, snow expected. Total snow
  accumulations 1 to 3 inches with locally up to 6 inches on the
  Camas Prairie. Winds gusting as high as 45 mph. For the Winter
  Storm Watch, heavy snow possible. Total snow accumulations between
  5 and 10 inches possible, locally lower amounts of 2 to 4 inches
  in the Lewis Clark Valley . Winds could gust as high as 45 mph.

* WHERE...Clarkston, Peck, Culdesac, Lewiston, Kamiah, Pomeroy,
  Winchester, Lapwai, Craigmont, Gifford, Lewiston Grade, Nezperce,
  Alpowa Summit, and Soldiers Meadow Road.

* WHEN...For the Winter Weather Advisory, from 1 AM to 4 PM PST
  Wednesday. For the Winter Storm Watch, from late Wednesday night
  through Friday afternoon.

* IMPACTS...Travel could be very difficult. Winter travel conditions
  could impact the Wednesday morning and evening commutes. Gusty
  winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Idaho, for the latest
road information in Idaho, call 5 1 1. In Washington, for the latest
travel information in Washington, go to https://wsdot.wa.gov/travel

Monitor the latest forecasts for updates on this situation.

[MossMan]

Jim’s going for it anyway! 

[MossMan]

It’s coming. 

[TT-SEA]

Arctic front snow on Thursday... this run is slower.   Temps don't go below freezing in Seattle until Thursday evening.  

[SilverFallsAndrew]

1 minute ago, TT-SEA said:

Total snow overnight per 18Z ECMWF... about half of what the GFS shows.    We need about 6 inches in downtown Portland tonight to trust the GFS snow amounts.

I’m in the purple. It’s sticking at Silver Falls now, could be a fun commute… 

[RentonHill]

GFS GFS GFS

[Perturbed Member]

7 minutes ago, TT-SEA said:

Total snow overnight per 18Z ECMWF... about half of what the GFS shows.    We need about 6 inches in downtown Portland tonight to trust the GFS snow amounts.

I would be pretty impressed if we manage a widespread 1 inch, especially downtown. The 18z GFS is completely coked out but even these Euro snow maps are almost always too generous with 33-34F snow. 

Should be lots of heavy big wet snowflakes falling though.  

[Doinko]

1 minute ago, TT-SEA said:

Arctic front snow on Thursday... this run is slower.   Temps don't go below freezing in Seattle until Thursday evening.  

Yeah a slight shift north

[Front Ranger]

21 minutes ago, Parrot said:

I'm no expert but as far as I was aware, arctic front events range from very marginal to localized at best. And the models are only calling for a trace with the front. Getting snow going into an event is not necessarily an event caused by the arctic front. But please corect me if I'm a bit off base...

Arctic front events can be very widespread down the Sound, with plentiful snow. This one doesn't look that way currently, but again, models struggle mightily with the convergence they create.

Examples: Feb 1989, Dec 1990, Jan 1996, Jan 2004, Nov 2006, Dec 2008, Nov 2010, Feb 2011, Feb 2019, Dec 2021

[RCola]

1 minute ago, TT-SEA said:

Arctic front snow on Thursday... this run is slower.   Temps don't go below freezing in Seattle until Thursday evening.  

Slower could mean less suppression on Saturday?

[RentonHill]

Looks juicier 

[FroYoBro]

1 minute ago, SilverFallsAndrew said:

I’m in the purple. It’s sticking at Silver Falls now, could be a fun commute… 

I expect to see some nice snow pictures on here from you tomorrow morning! 

[Olive1010]

11 minutes ago, TT-SEA said:

Total snow overnight per 18Z ECMWF... about half of what the GFS shows.    We need about 6 inches in downtown Portland tonight to trust the GFS snow amounts.

Lmao idk man, the nws Portland is saying a dusting on grass surfaces. 

[HuskyMaestro]

44F here but felt waaay colder walking back to my car with all the wind around. Brrr! 

[TT-SEA]

Going to be slight northward shift which basically undoes the southward shift on the 12Z run.   This run looks like the 06Z run last night.

[Doinko]

Just now, TT-SEA said:

Going to be slight northward shift which basically undoes the southward shift on the 12Z run.   This run looks like the 06Z run last night.

I think it should still be good here in PDX

[Olive1010]

You guys really think Portland will receive more than an inch tonight on the ground? Temps hover at like 31-35 tonight.

[TT-SEA]

Friday afternoon

[AbbyJr]

From this:

To this:

Sad climo.

[Requiem]

2 minutes ago, Olive1010 said:

Lmao idk man, the nws Portland is saying a dusting on grass surfaces. 

Pop quiz what do the NWS Portland use to determine their forecasts (hint it starts w an M and ends with an S)

[Doinko]

1 minute ago, TT-SEA said:

Friday afternoon

What are temps at this time?

[SilverFallsAndrew]

1 minute ago, TT-SEA said:

Friday afternoon

That’s still pretty far south compared to the worlds new top model the GFS!

[Perturbed Member]

This track on the 18z Euro should be pretty similar to last night's Euro/ICON/UKMET camp, which is also about the same as what the GraphCast shows. Pretty far south with NW OR/SW WA at the northern edge of the main precip shield. 

[hawkstwelve]

FWIW, NWS Sioux Falls is favoring the GFS/GEFS solution for out here. 

Amounts are looking to remain on the light side, generally
less than an inch, though there is considerable uncertainty amongst
the deterministic and ensemble guidance. Looking at clustering
analysis, it is shown that there is a general pattern where two of
the clusters are dominated by the ECMWF, and the other two dominated
by the GEFS, with the GEPS split fairly evenly amongst the 4 cluster
solutions. What this means is that model biases are determining the
sorting process, so it`s difficult to put more weight on any one
solution. So, currently we are favoring the GEFS solution which
keeps the track of the low further to the south, while the ECMWF has
a track further to the north thus resulting in more snow, though
still generally below 2 inches.

[TT-SEA]

This run is actually a small southward shift from the 00Z run last night.   

[Timmy]

Tim, I need you to post these euro images a little faster. Thx

[Olive1010]

3 minutes ago, Requiem said:

Pop quiz what do the NWS Portland use to determine their forecasts (hint it starts w an M and ends with an S)

ECMWF?

[Requiem]

All in all this will look similar to the 00z from last night 

[MR.SNOWMIZER]

5 minutes ago, TT-SEA said:

Going to be slight northward shift which basically undoes the southward shift on the 12Z run.   This run looks like the 06Z run last night.

Just a wobble. 

[TT-SEA]

2 minutes ago, Doinko said:

What are temps at this time?