PNW February 2023 Weather Discussion - Meteorological winter finale

[MR.SNOWMIZER]

1 minute ago, RentonHill said:

Lol pretty darn close. A little more here. In past events euro has been light on amounts so we will see. 

[SilverFallsAndrew]

13 minutes ago, BLI snowman said:

Looks like 31 at PDX and 35 at SEA should hold as their highs today.

36 at SLE. Not bad. Might be a record I’ll have to check. 

[TigerWoodsLibido]

[PuyallupChris]

53 minutes ago, NWbyNW said:

They are expecting some snow in Western Washington this weekend.  Here are some predicted accumulations by Sunday morning.

 

Swamp alert. 

Hard to grade this winter for me also. Not good, but I can't call it a complete wash. A number of 1/4" - 1/2" snowfalls, and the one "big" snow seemed to drop only a few inches here in the valley that disappeared from the roads almost instantly. 

Meanwhile, a LOT of hype and close calls which make me feel a little more sour grapes than I honestly should.

[MR.SNOWMIZER]

Hey what happened to brian in Leavenworth?

[lowlandsnow]

GEFS is better

[LowerGarfield]

1 hour ago, MossMan said:

Well my mother in law picks great times to come visit in the winter…Last time she was here in the winter it was the time between Christmas and New Years 2021…And she is arriving today and staying through mid week next week! She lives in Arizona!

She is always welcome to visit if she brings the snow to you.

Here I just snuck over to check the temp and I'm at 23F. Which is the same it was about 2:30 or so and the highest I've seen all day. At this point I've all but clinched a sub freezing day here.

[MR.SNOWMIZER]

7 minutes ago, lowlandsnow said:

GEFS is better

The difference now with these maps is we are in the pattern.  D**n good chance a lot of this snow is possible and could happen.

[Mr Marine Layer]

Question for Phil. Is the polar vortex causing this?

[Mr Marine Layer]

10 minutes ago, MR.SNOWMIZER said:

Hey what happened to brian in Leavenworth?

Snowed in?

[FroYoBro]

I managed a sub freezing high here as well. Amazing event!

[Cold Snap]

Euro is showing a decent convergence zone after the front comes through.

[MossMan]

12 minutes ago, MR.SNOWMIZER said:

Hey what happened to brian in Leavenworth?

I wondered the same thing so I went back to his last post in January and he was really upset about another forum member going off on some met that is on Twitter or something that he respected? I think he got upset and left the forum. 

Edited February 24 by MossMan

[SilverFallsAndrew]

Our high ended up being 28 today, afternoon high of 27. Hoping things clear up and we plummet. 

[SouthHillFrosty]

19 minutes ago, RentonHill said:

Close to a non event wow. Any grey “snow” is a non event and marginal at best 

Edited February 24 by SouthHillFrosty

[Doinko]

21 minutes ago, RentonHill said:

How's the map for OR?

[SouthHillFrosty]

Icon looked ok

[MossMan]

It’s over. 

[MossMan]

Just now, SouthHillFrosty said:

Icon looked ok

It’s not over! 

[WeatherGeek2022]

22 minutes ago, RentonHill said:

no good.

 

 

throw it out.

[mjreich]

5 hours ago, Phishy Wx said:

NBM MODEL INPUTS

 

NBM MODEL INPUTS: These are the model inputs and sources for the NBM v4.1. Model names with an * are new to NBM v4.1

Model Name	Agency	Resolution	Cycles/Day	Members	Cycles Updated
ACCESS-G	BoM Australia	12 km	2x	1	07, 19
ACCESS-GE *	BoM Australia	35 km	4x	18	02, 08, 14, 20
EC MOSD	ECMWF	N/A (Stations only)	2x	1	08, 20
EC MOSE	ECMWF	N/A (Stations only)	2x	50	09, 21
ECMWFD	ECMWF	25 km	2x	1	08, 20
ECMWFE	ECMWF	50 km	2x	50	09, 21
GDPS	CMC Canada	25 km	2x	1	05, 17
GEPS	CMC Canada	50 km	2x	20	07, 19
GEFS	NCEP	25 km	4x	30	01, 07, 13, 19
GFS	NCEP	13 km	4x	1	05, 11, 17, 23
GFS MOS STN	NCEP	N/A (Stations only)	4x	1	00, 06, 12, 18
GLMP	NCEP	2.5 km	24x	1	Every hour
GMOS	NCEP	2.5 km	2x	1	07, 19
HiResW ARW	NCEP	3 km	2x	1	04, 16
HiResW ARW MEM2	NCEP	3 km	2x	1	04, 16
HiResW FV3	NCEP	3 km	2x	1	04, 16
HMON	NCEP	1.5 km	4x	1	00, 06, 12, 18
HREF	NCEP	5 km	2x	8	07, 19
HRRR	NCEP	3 km	24x	1	Every hour
HRRR-EXT	NCEP	3 km	4x	1	03, 09, 15, 21
HWRF	NCEP	1.5 km	4x	1	00, 06, 12, 18
LAMPMOS	NCEP	N/A (Stations only)	24x	1	Every hour
MELD	NCEP	2.5 km	24x	1	Every hour
MMEBC	NCEP/WPC	5 km	4x	1	00, 06, 12, 18
NAM	NCEP	12 km	4x	1	03, 09, 15, 21
NAMMOS	NCEP	N/A (Stations only)	4x	1	03, 09, 15, 21
NAMNest	NCEP	3 km	4x	1	03, 09, 15, 21
NAVGEMD	FNMOC	50 km	4x	1	00, 06, 12, 18
NAVGEME	FNMOC	50 km	2x	20	06, 18
RAP	NCEP	13 km	24x	1	Every hour
RAP-EXT	NCEP	13 km	4x	1	00, 06, 12, 18
RDPS	CMC Canada	10 km	4x	1	04, 10, 16, 22
REPS	CMC Canada	15 km	2x	20	07, 19
RTMA	NCEP	2.5 km	24x	1	every hour
QMD	MDL	2.5 km	4x	1	01, 07, 13, 19
SREF	NCEP	16 km	4x	24	01, 07, 13, 19
REWPS *	CMC Canada	2.5 km	2x	20	05, 17
GEPS Waves	CMC Canada	25 km	2x	20	07, 19
NAVGEMD Waves	FNMOC	100 km	2x	1	07, 19
NAVGEME Waves	FNMOC	50 km	2x	20	07, 19
GFS WW3D Waves	NCEP	25 km	4x	1	05, 11, 17, 23
GEFS WW3E Waves	NCEP	25 km	4x	30	01, 07, 13, 19
WW3D HIRES Waves	NCEP	9-17 km	4x	1	05, 11, 17, 23
GLWU Waves	NCEP	2.5 km	4x	1	02, 08, 14, 20

NBM is quite an interesting product! Their weighting algorithm is moderately complex and dynamic, though does has some drawbacks as we saw yesterday. For those who don't know, NBM is an attempt by NOAA to create a super probabilistic forecast model that ingests output from all the models above and outputs forecast guidance for local offices that help them to gauge the relative odds of particular weather outcomes. The 'special sauce' is the post-processing, normalization and weighting that they do based on a number of factors, but most novelly, factoring in 'bias' or deviation of the forecast from historical observations (both short and long term) to adjust relative weights given to specific model outputs. Rather than static weights, it uses a 'learning' model that adjusts weights based on a number of dynamic factors for every data product release. Here's a somewhat dated visual of the weighting algorithm: 

(MAE is mean absolute error).

I'm not sure about the latest version released last month, but previous NBM versions have used a 6-12 hour observation window for calculating MAEs and bias deltas (large recent deviations from observed will decrease model weighting), as well as factoring in model run consistency over the previous 7 days (larger run to run variance will necessarily decrease the model weight).

So a couple of thoughts. First off, NBM is specifically designed to be a nationally consistent output, meaning that the entire thing runs for the entire country without regional or mesoscale differences. This clearly is a drawback when trying to predict fairly local effects like the gorge where few models are going to have the spatial resolution to accurately model small details like convergence zones.

Second, the biasing model is trained based on historical deviations, rather than evaluated skill forecasting predicted weather patterns. In other words, the bias weight will factor in how a model has performed in the last 7 days, rather than 'how does the model perform for a given set of weather features.' There is nothing inherently wrong with this approach, and given the limitations with characterizing future weather projections it makes a lot of sense, but does have drawbacks. Specifically, with a pattern change like we saw yesterday: the forecast skill in the previous 5 days has little correlation to the skill forecasting the next 24 hours.

So, why the lack of skill with the storm last night when some of the models did show big snow? I think a couple of obvious reasons. First off, most of the models flipped late to show big snow. This would have the effect of increasing the observed model variance (or uncertainty), leading to a lower weight in the NBM.

Another factor was likely data ingestion. This is a national model, and for most of the country, input data is very good because weather patterns are moving over lots of land based sensors which can provide the core observation data used to weight the model. For us on the west coast, this is a bug not a feature, because the Pacific Ocean is a big data dead zone (largely we don't have much idea about the actual temp/pressure profiles except for a few buoys). So, when models flip at the last minute like they did last night, it's usually a data issue - better data has been used to initialize the models as weather features get closer to shore. But for rest of the country where weather data is consistent and good, last minute changes are an indication of model inconsistency rather than better data = poor model performance.

Overall, I think NBM is a good product and provides a nice additional tool for NWS staff to tailor their local forecasts. But, like we saw last night, without understanding its limitations in specific scenarios (like we have with marginal snow events) the NBM can provide overly confident forecasts when in fact the confidence is decreasing. I think there's a lot of promise to this approach (and in fact NOAA is borrowing a lot from what commercial folks are already doing in big adaptive model development in finance and epidemiology): most obviously is another layer that weights model forecast based on prospective mesoscale patterns and allows for dynamic local weighting.

[Gummy]

2 minutes ago, SouthHillFrosty said:

Close to a non event wow. Any grey “snow” is a non event and marginal at best 

Unfortunately true. Add in the street temps, since the highs will be close to 40 in some locations, and this event is on the brink.

[joelgombiner]

9 minutes ago, Mr Marine Layer said:

Question for Phil. Is the polar vortex causing this?

I have the same question. 

[SilverFallsAndrew]

Corvallis getting hit hard again. 

[MR.SNOWMIZER]

10 minutes ago, SouthHillFrosty said:

Close to a non event wow. Any grey “snow” is a non event and marginal at best 

You will be fine. A couple inches no problem for you.

[smerfylicious]

11 minutes ago, MossMan said:

I wondered the same thing so I went back to his last post in January and he was really upset about another forum member going off on some met that is on Twitter or something that he respected? I think he got upset and left the forum. 

Sure seems that way. Sucks though, he's a great poster and the only one here that can make me more snow jealous than you can haha

[SouthHillFrosty]

5 minutes ago, Gummy said:

Unfortunately true. Add in the street temps, since the highs will be close to 40 in some locations, and this event is on the brink.

If this event is on life alert, Tim is happy to provide CPR to anybody

[MR.SNOWMIZER]

6 minutes ago, Gummy said:

Unfortunately true. Add in the street temps, since the highs will be close to 40 in some locations, and this event is on the brink.

It will deliver. The airmass will be very dry and still chilly when precip arrives. Timing is good, this will be a nice regional event.

[joelgombiner]

3 minutes ago, mjreich said:

NBM is quite an interesting product! Their weighting algorithm is moderately complex and dynamic, though does has some drawbacks as we saw yesterday. For those who don't know, NBM is an attempt by NOAA to create a super probabilistic forecast model that ingests output from all the models above and outputs forecast guidance for local offices that help them to gauge the relative odds of particular weather outcomes. The 'special sauce' is the post-processing, normalization and weighting that they do based on a number of factors, but most novelly, factoring in 'bias' or deviation of the forecast from historical observations (both short and long term) to adjust relative weights given to specific model outputs. Rather than static weights, it uses a 'learning' model that adjusts weights based on a number of dynamic factors for every data product release. Here's a somewhat dated visual of the weighting algorithm: 

(MAE is mean absolute error).

I'm not sure about the latest version released last month, but previous NBM versions have used a 6-12 hour observation window for calculating MAEs and bias deltas (large recent deviations from observed will decrease model weighting), as well as factoring in model run consistency over the previous 7 days (larger run to run variance will necessarily decrease the model weight).

So a couple of thoughts. First off, NBM is specifically designed to be a nationally consistent output, meaning that the entire thing runs for the entire country without regional or mesoscale differences. This clearly is a drawback when trying to predict fairly local effects like the gorge where few models are going to have the spatial resolution to accurately model small details like convergence zones.

Second, the biasing model is trained based on historical deviations, rather than evaluated skill forecasting predicted weather patterns. In other words, the bias weight will factor in how a model has performed in the last 7 days, rather than 'how does the model perform for a given set of weather features.' There is nothing inherently wrong with this approach, and given the limitations with characterizing future weather projections it makes a lot of sense, but does have drawbacks. Specifically, with a pattern change like we saw yesterday: the forecast skill in the previous 5 days has little correlation to the skill forecasting the next 24 hours.

So, why the lack of skill with the storm last night when some of the models did show big snow? I think a couple of obvious reasons. First off, most of the models flipped late to show big snow. This would have the effect of increasing the observed model variance (or uncertainty), leading to a lower weight in the NBM.

Another factor was likely data ingestion. This is a national model, and for most of the country, input data is very good because weather patterns are moving over lots of land based sensors which can provide the core observation data used to weight the model. For us on the west coast, this is a bug not a feature, because the Pacific Ocean is a big data dead zone (largely we don't have much idea about the actual temp/pressure profiles except for a few buoys). So, when models flip at the last minute like they did last night, it's usually a data issue - better data has been used to initialize the models as weather features get closer to shore. But for rest of the country where weather data is consistent and good, last minute changes are an indication of model inconsistency rather than better data = poor model performance.

Overall, I think NBM is a good product and provides a nice additional tool for NWS staff to tailor their local forecasts. But, like we saw last night, without understanding its limitations in specific scenarios (like we have with marginal snow events) the NBM can provide overly confident forecasts when in fact the confidence is decreasing. I think there's a lot of promise to this approach (and in fact NOAA is borrowing a lot from what commercial folks are already doing in big adaptive model development in finance and epidemiology): most obviously is another layer that weights model forecast based on prospective mesoscale patterns and allows for dynamic local weighting.

Brilliant post. My takeaway is that the NBM performs worse during pattern changes, and that region-specific blends would be better than a national blend. 

[TacomaWx]

36/27 temp spread today…suns not down yet and it’s already 33. Going to get very cold tonight even without snowcover. 

[SouthHillFrosty]

1 minute ago, MR.SNOWMIZER said:

You will be fine. A couple inches no problem for you.

Oh Ik I stayed earlier that I am in full weenie mood for this weekend 

[TacomaWx]

3 minutes ago, MR.SNOWMIZER said:

You will be fine. A couple inches no problem for you.

Also easy to forget overrunning events are almost always underdone. I’d be surprised if we got less than 1.5-2” 

[joelgombiner]

Current PV 

[MR.SNOWMIZER]

Areas that will struggle with snow sunday will be places right near the sound and less than 200ft elevation.

[Doinko]

Midnight high of 31 at PDX with full sunshine throughout the day is crazy. Last time there was a subfreezing high this late was the 29 degree high in March 1960 which involved precip during the day

[MR.SNOWMIZER]

Just now, TacomaWx said:

Also easy to forget overrunning events are almost always underdone. I’d be surprised if we got less than 1.5-2” 

widespread 2-5 inches easy. 4-8 around the canal and another 4-8 around the canal sunday night through wednesday.

[TT-SEA]

6 minutes ago, TacomaWx said:

Also easy to forget overrunning events are almost always underdone. I’d be surprised if we got less than 1.5-2” 

This is such a strange overrunning situation.   Normally there is cold air in place and the system is coming in from the southwest with an east wind ahead of the system and an air mass battle ensues.    With this situation... there is basically no cold air left on Saturday afternoon.   The only thing that makes this event happen is the dry air in place.   There won't be an extended air mass battle this time.   The wind is roaring from the south by 4 a.m. on Sunday immediately after the front passes.    But its polar maritime air mass so it won't warm up significantly either.    Strange deal.

[Front Ranger]

5 minutes ago, MR.SNOWMIZER said:

Areas that will struggle with snow sunday will be places right near the sound and less than 200ft elevation.

Timing of precip arrival should help at least.

[snow_wizard]

Managed to pull off a high of 32 here today for the latest freezing max temp I've ever recorded here.  To do that without snow cover is really quite something this late in the season.  No doubt the east wind helped out considerably.

[TacomaWx]

This winters a B+ for me so far. Might get to A- status depending on how the sunday system and the potential snows later next week works out. 
 2 sub freezing highs, 13 sub 40 highs so far with 2 significant arctic outbreaks. Rare ice storm.  Haven’t managed a big snow event so far this winter and it likely isn’t in the cards…but I can’t complain. A lot of small events which were all fun. Can’t remember a year with such a number of light snowfalls with more likely coming up. 
 11/29 0.7”

11/30 1.2”

12/1   0.8”

12/2  1.2”

12/3 0.2”

12/4 1.1”

12/20 0.3”

12/21 0.5”

1/28 TR.

1/31 TR.

2/13 0.2”

2/22 TR.

2/23 0.2”

 

[snow_wizard]

5 minutes ago, TT-SEA said:

This is such a strange overrunning situation.   Normally there is cold air in place and the system is coming in from the southwest with an east wind ahead of the system and an air mass battle ensues.    With this situation... there is basically no cold air left on Saturday afternoon.   The only thing that makes this event happen is the dry air in place.   There won't be an extended air mass battle this time.   The wind is roaring from the south by 4 a.m. on Sunday immediately after the front passes.    But its polar maritime air mass so it won't warm up significantly either.    Strange deal.

This is a weird one.  Models have been very consistent on widespread snowfall, but have waffled a bit on some details.  Interestingly the GFS improved with snow amounts on every run today while the ECMWF improved 6z over 0z, but then dropped some on the 12z and 18z.

Another weird thing is after the south wind it freezes again Sunday night.

[Front Ranger]

8 minutes ago, TacomaWx said:

36/27 temp spread today…suns not down yet and it’s already 33. Going to get very cold tonight even without snowcover. 

Looks like this thing could actually rival 2011 in spots. Beastly.

And it's not localized at all, either. I posted it in the mountain west thread, but DEN put up a 7/-11 today, which is historic for this late in the season - only one event, Feb 1962, has been colder later.

Late Feb 2011, on the other hand, was basically a non event here.

[MossMan]

35/25 on the day, currently 31. DP of 18. My current snow situation. 

[Cold Snap]

8 minutes ago, MR.SNOWMIZER said:

widespread 2-5 inches easy. 4-8 around the canal and another 4-8 around the canal sunday night through wednesday.

How do you think I will do next week after the Sunday storm at 408’ elevation?

[SilverFallsAndrew]

The Sunday system is a pretty straightforward snow maker up here. Not usually something that produces snow below 500-1000’, I would be surprised if Salem had accumulating snow, but who knows the worm has turned. 

[snow_wizard]

1 minute ago, TacomaWx said:

This winters a B+ for me so far. Might get to A- status depending on how the sunday system and the potential snows later next week works out. 
 2 sub freezing highs, 13 sub 40 highs so far with 2 significant arctic outbreaks. Rare ice storm.  Haven’t managed a big snow event so far this winter and it likely isn’t in the cards…but I can’t complain. A lot of small events which were all fun. Can’t remember a year with such a number of light snowfalls with more likely coming up. 
 11/29 0.7”

11/30 1.2”

12/1   0.8”

12/2  1.2”

12/3 0.2”

12/4 1.1”

12/20 0.3”

12/21 0.5”

1/28 TR.

1/31 TR.

2/13 0.2”

2/22 TR.

2/23 0.2”

 

I think A and A- are out of reach.  Just comparing to what an A or A- winter would be historically speaking.  I think B+ is still doable though.

BTW...a lot of snow chances are coming and one of them could be a big one.  The EPS and GEFS are just ridiculous with 850s sustained in the -5 to -8 bracket for the next two weeks.

[TacomaWx]

1 minute ago, Front Ranger said:

Looks like this thing could actually rival 2011 in spots. Beastly.

And it's not localized at all, either. I posted it in the mountain west thread, but DEN put up a 7/-11 today, which is historic for this late in the season - only one event, Feb 1962, has been colder later.

Late Feb 2011, on the other hand, was basically a non event here.

Atleast IMBY and most of western WA this ain’t close to 2011. We had a 30/25 day on 2/25/11…coldest day will likely be 36/27 today on this one. Really impressive numbers in SW BC and down in southern WA/OR. 

[SouthHillFrosty]

 

[Doinko]

8 minutes ago, snow_wizard said:

Managed to pull off a high of 32 here today for the latest freezing max temp I've ever recorded here.  To do that without snow cover is really quite something this late in the season.  No doubt the east wind helped out considerably.

Afternoon high of 28 at Hillsboro today.

[snow_wizard]

4 minutes ago, Front Ranger said:

Looks like this thing could actually rival 2011 in spots. Beastly.

And it's not localized at all, either. I posted it in the mountain west thread, but DEN put up a 7/-11 today, which is historic for this late in the season - only one event, Feb 1962, has been colder later.

Late Feb 2011, on the other hand, was basically a non event here.

I wasn't able to pull off a freezing max in 2011 even with snow on the ground.  This airmass is actually colder...at least at the low levels.