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PNW February 2023 Weather Discussion - Meteorological winter finale


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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.

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Corvallis getting hit hard again. 

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Snowfall                                  Precip

2022-23: 95.0"                      2022-23: 17.39"

2021-22: 52.6"                    2021-22: 91.46" 

2020-21: 12.0"                    2020-21: 71.59"

2019-20: 23.5"                   2019-20: 58.54"

2018-19: 63.5"                   2018-19: 66.33"

2017-18: 30.3"                   2017-18: 59.83"

2016-17: 49.2"                   2016-17: 97.58"

2015-16: 11.75"                 2015-16: 68.67"

2014-15: 3.5"
2013-14: 11.75"                  2013-14: 62.30
2012-13: 16.75"                 2012-13: 78.45  

2011-12: 98.5"                   2011-12: 92.67"

It's always sunny at Winters Hill! 
Fighting the good fight against weather evil.

 

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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

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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 😂

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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.

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We come from the land of the ice and snow.

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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: image.thumb.png.53d6481958ea8a43351ad4362c2a2a1c.png

(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. 

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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.

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We come from the land of the ice and snow.

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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.

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**REPORTED CONDITIONS AND ANOMALIES ARE NOT MEANT TO IMPLY ANYTHING ON A REGIONAL LEVEL UNLESS SPECIFICALLY STATED**

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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.

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Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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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”


 

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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.

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Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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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.

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A forum for the end of the world.

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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?

2023 - 2024 Cold Season Stats

Total Snowfall - 0.75”

Max Snow Depth - 0.5”

Coldest High Temp - 21 (Jan 13)

Coldest Low Temp - 9 (Jan 13)

Number of Freezes - 48

Sub-40 highs - 12

Highs 32 or lower - 3

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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. 

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Snowfall                                  Precip

2022-23: 95.0"                      2022-23: 17.39"

2021-22: 52.6"                    2021-22: 91.46" 

2020-21: 12.0"                    2020-21: 71.59"

2019-20: 23.5"                   2019-20: 58.54"

2018-19: 63.5"                   2018-19: 66.33"

2017-18: 30.3"                   2017-18: 59.83"

2016-17: 49.2"                   2016-17: 97.58"

2015-16: 11.75"                 2015-16: 68.67"

2014-15: 3.5"
2013-14: 11.75"                  2013-14: 62.30
2012-13: 16.75"                 2012-13: 78.45  

2011-12: 98.5"                   2011-12: 92.67"

It's always sunny at Winters Hill! 
Fighting the good fight against weather evil.

 

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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.

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Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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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. 

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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.

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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.

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Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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2 minutes ago, TacomaWx said:

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. 

I did 32/24 today.  I think 2011 had more of a northerly component which favors your area for colder max temps.  This one is a bit more of an easterly component which favors my area for cold max temps.  That one also had snow cover to help with the temps.

Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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The 12z ECMWF and 12z EPS were both showing another pretty legit cold airmass around day 10 with 850s falling to -8 or so.  We are in a groove!

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Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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