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Have NWAC ratings been reduced?
- haggis
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24 Dec 2015 08:37 #225431
by haggis
Have NWAC ratings been reduced? was created by haggis
So I'm curious. NWAC is reporting considerable across the board on 23rd and 24th Dec with all of this new snow, and its a crap load as we know. Light with denser snow falling at the pass now. Crystal was pretty light yesterday and cold so not counting that area. Contradicting this we have the list below.
1 - The I90 pass is closed for avalanche danger, collision removal etc.
2 - Stevens pass is closed for avalanche control
3 - SAR are not searching for Monte Busby due to avalanche hazard.
In years gone by something of this scale would certainly have been on the High rating. I can only recall extreme being a big snowfall followed immediately by a rain event.
Has NWAC reduced the High rating to considerable?
1 - The I90 pass is closed for avalanche danger, collision removal etc.
2 - Stevens pass is closed for avalanche control
3 - SAR are not searching for Monte Busby due to avalanche hazard.
In years gone by something of this scale would certainly have been on the High rating. I can only recall extreme being a big snowfall followed immediately by a rain event.
Has NWAC reduced the High rating to considerable?
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- joecat2
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24 Dec 2015 08:49 #225433
by joecat2
Replied by joecat2 on topic Re: Have NWAC ratings been reduced?
From being out there I think the NWAC ratings are on target or some days have been a bit overstated recently. What is unusual up to yesterday there has been very little wind relative to the amount of snowfall. Thus less slabbiness and hazard. Maybe the DOT has a simple formula based on snowfall amount, not the NWAC hazard rating. The 23rd seemed to be windier than most of the last week. It is hard to know at Snoqualmie with the Alpental wind gauge out for about a year and the Keechulus gauge, which is less relevant, does not work in west winds.
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- haggis
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24 Dec 2015 09:00 #225434
by haggis
Replied by haggis on topic Re: Have NWAC ratings been reduced?
The winds have been fairly light with the recent snow around Stevens pass. Without the benefit of the telemetry or ski area reports at Snoq pass its fair to assume similar there. Crystal did have reasonable gusts over 50mph which is a lot but it was getting hammered by skiers yesterday and I saw or heard of nothing odd in the ski area, steep slopes I was on were stable. This would indicate a rating consistent with the NWAC one so maybe its the other authorities that are looking at different metrics as you say.
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- Blizz Mountain
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24 Dec 2015 11:50 #225440
by Blizz Mountain
Replied by Blizz Mountain on topic Re: Have NWAC ratings been reduced?
haggis... I was thinking along the same lines as you... seemed like conditions have been a bit more dangerous than 'considerable'. A few days ago I saw a lot of small natural new soft snow slides on steeper microfeatures as well as all the other news out there - several unconsolidated tree well incidents and deaths in the west the past few weeks also. I am by no means an expert in snow science or avy conditions - so not to contradict the experts or those with more experience... just a gut feeling that it's a bit worse.
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- Jim Oker
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24 Dec 2015 19:50 #225448
by Jim Oker
Replied by Jim Oker on topic Re: Have NWAC ratings been reduced?
I assume the ratings address the chance of avalanches and not the potential size if avalanches do occur - is that true? With what I've seen while out there (as of Tuesday, before travelling east in time to miss more heaps of snow), what scares me is more the sheer depth of snow before the last solid layer, versus the touchiness of the recent snow. With so much snow hanging above the highways, of course DOT wants to bring down what they can, regardless of the probability of natural slides.
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- Micah
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24 Dec 2015 21:38 #225449
by Micah
From the description of the danger scale at nwac.us:
The danger is a combination of the expected likelihood, size, and distribution of avalanches.
Replied by Micah on topic Re: Have NWAC ratings been reduced?
I assume the ratings address the chance of avalanches and not the potential size if avalanches do occur - is that true?
From the description of the danger scale at nwac.us:
The danger is a combination of the expected likelihood, size, and distribution of avalanches.
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- Charlie Hagedorn
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24 Dec 2015 23:40 #225451
by Charlie Hagedorn
Replied by Charlie Hagedorn on topic Re: Have NWAC ratings been reduced?
My experiences in the field during this cycle have been in line with NWAC predictions. Each day out, we didn't see the truly reactive instability I associate with 'High' danger. There haven't been reports of any low-likelihood, huge-consequence strata, either.
Sure is a lot of snow, though.
Sure is a lot of snow, though.
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- Kneel Turner
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25 Dec 2015 09:16 #225455
by Kneel Turner
Replied by Kneel Turner on topic Re: Have NWAC ratings been reduced?
Have there been many reports of large natural avalanches?
Based on my observations they are right on. There is an amazing amount of new unconsolidated snow, but from what I've seen, it's staying put unless directly influenced on suspect terrain. Have you noticed the flocking on the trees? This snow is pretty comfortable sitting where it fell.
I dont think forecasting avalanche danger takes into consideration the threat of tree well immersion and deep snow safety (at least I hope it doesn't).
An avalanche's threat to me and my ski buddies is only one small part of my personal risk/benefit analysis.
Based on my observations they are right on. There is an amazing amount of new unconsolidated snow, but from what I've seen, it's staying put unless directly influenced on suspect terrain. Have you noticed the flocking on the trees? This snow is pretty comfortable sitting where it fell.
I dont think forecasting avalanche danger takes into consideration the threat of tree well immersion and deep snow safety (at least I hope it doesn't).
An avalanche's threat to me and my ski buddies is only one small part of my personal risk/benefit analysis.
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