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[lucky luke]

wet snow avalanche are the worse, they happen every where without warning. There was a huge one in huntington ravine and people was kill many years ago. Wet avalanche are not just caused by rain, but by heavy snow. Moisture in the air are absorbed by the snow and the pack weight more...so the danger increase.

in a snow storm, the snow flakes are light weight. The crystal flake is sharp and the snow hold better. From the direction of the wind, we can know where a corniche is form and we can see the direction of avalanches because many small of them occur without too much danger.

So can we explain that today the danger is moderate (can be trigger by human and natural are unlikely), and in a snow storm it is extremely dangerous?

[kenreville]

"So can we explain that today the danger is moderate as it can be trigger by human and low as natural and in a snow storm it is extremely dangerous?"

As difficult as it it to understand just what it is you are asking, methinks I've figured it out.

It's because of the ethics of the avalanche.
Fresh snow is much more trad than that sporty wind slab.

[JJ Jameson]

Ken, for the WIN.
I wouldn't have the slightest clue where to even start with a response to Luke's post, as I have NO IDEA WhAT THE F HIS POST WAS ABOUT!

[carp]

Methinks that I'm waaaaaaaaaaaay too sober to even begin to understand Luke's post. However, I have some bourbon, scotch, and whiskey on hand, so...

[bennybrew]

http://www.nytimes.com/projects/2012/snow-fall/#/?part=tunnel-creek

an interesting article and an interesting presentation of information.

takes a while to get through, though.

[DMan]

LL, I'm glad you are interested in avalanches... I think you would benefit from a actual course as you have a lot of knowledge, but also a lot of misconceptions... to pull out a few:

"wet snow avalanche are the worse, they happen every where without warning."

Warning = a noticeably wet snowpack + warm temps (above freezing) and sometimes strong solar radiation (especially southern aspects). Rain is more dangerous on a winter snowpack vrs. a spring snowpack... but rain is never great...

"Wet avalanche are not just caused by rain, but by heavy snow." - kind of a silly statement. It was rain and/or warm temps that made the snow heavy...

"Moisture in the air is absorbed by the snow and the pack weight more...so the danger increase."- talking fancy here... unless by "moisture in the are is absorbed" you mean "when rain hits the snow it is absorbed"...

"in a snow storm, the snow flakes are light weight."- Depending on the snowstorm, and climate, i.e Maritime, Continental, Intermountain, the snow in a snowstorm can be very heavy and wet... we get wet snow all the time...

"The crystal flake is sharp and the snow hold better." - Sharper crystals are actually less likely to bond together, creating point release avalanches, sluffs, and potentially weak layers underneath if stronger snow falls on top...

"From the direction of the wind, we can know where a corniche is form and we can see the direction of avalanches because many small of them occur without too much danger." - Close, but you state this backwards. It would be more accurate to say "from looking at cornices we can see what the direction of the wind was, and maybe figure out where wind slabs have formed"...

"So can we explain that today the danger is moderate (can be trigger by human and natural are unlikely), and in a snow storm it is extremely dangerous?" - Snow storms are typically dangerous as you can get widespread avalanches in many places... slabs, loose snow, wet slab... it all depends... so generalizing is not often helpful when learning to travel in avalanche terrain....

You've certainly read some books about avalanche danger, and you have a basic understanding. Be careful of making broad assumptions... as an old Appalachian proverb says;

"It's not what you don't know that will get you killed... it's what you think you know that just ain't so"....

@ Bennybrew, nice graphics and glad it brings the problem more into the public eye, but lacking some serious critique on the social pressures and human factors that drove those 16 people into that terrain given those conditions...

Since we're talking avalanches, I just got back a couple days ago from a great course in the Cascades...

http://davidlottmann.wordpress.com/2013/01/14/stevens-pass-instructor-training-course/

[Admin Al]

I read this. great story... it was also about the crowd mentality.

http://www.nytimes.com/projects/2012/snow-fall/#/?part=tunnel-creek

an interesting article and an interesting presentation of information.

takes a while to get through, though.

[lucky luke]

I read this, great story... it was also about the crowd mentality.

Yes. and one of them was an experience skier. It is mostly what I am saying. It is more dangerous after a snow storm than in the snow storm. The avalanche was tree feet deep and in a carve tunnel, the sky was grey, but there is no snow fall I think. People get out to have fun in the powder.

In the article, they state that the cause of the avalanche was: "The energy raised the temperature of the snow a couple of degrees, and the friction carved striations high in the icy sides of the canyon walls."

I am sorry for dman who never shovel roof in march. He will know that, in a sunny day, the humidity of warm air is absorbed (1. To take (something) in through or as through pores or interstices.) by the snow. In sunny day, the snow pack is heavier in the afternoon than in the morning even if there is no rain. It can be as much as 1.5 more heavier in the afternoon without rain...and it is not because I was tired.

I think that what happen is warm weather change the form of the crystal in the snow pack and reduce the friction of them. As the humidity increase, the pack gained weight to a breaking point. There is no course or technique to evaluate that because it can occur in two or three hours (second man to do all the 14 000meters state that). It began with one crystal that three, tens and millions of them. Only experience can told you. (the reason of my post it is to find climber and train to gain experience)

In the story, the woman wore a safety device. It seems it save her life.     

[DMan]

It is more dangerous after a snow storm than in the snow storm.

This statement is flawed. More people get caught in avalanches after the snow storm because less people venture out during the storm when danger is obvious. In a way you are correct, as many people, especially skiers, get caught by avalanches after the storms, during mild blue sky weather... so many that it has been labeled "Blue Sky Syndrome", i.e. people take greater risks when the weather is nice out...

In sunny day, the snow pack is heavier in the afternoon than in the morning even if there is no rain. It can be as much as 1.5 more heavier in the afternoon without rain...and it is not because I was tired.   

Again, you make assumptions from your basic understanding of mountain snowpacks. You've read enough to think you know what you are saying, but you miss some factual info in the re-telling of what you have read. First, solar radiation itself does not add any weight or mass to the existing snow. Solar radiation, plus warm temps, can melt the surface layers and cause the existing snow to become more dense "mashed potatoes" as we call it around here... no weight or moisture has been added to the snowpack, per your humidity transfer comments. The top layers have become more dense, and in certain situations this can lead to instability in the snowpack, but is not in and of itself a bad thing... it's this process that ultimately leaves us with a stable Spring snowpack and 1000+ people in Tuckerman Ravine with no beacon (and that's OK under those conditions)...

There is no course or technique to evaluate that because it can occur in two or three hours... Only experience can told you.

There is plenty of research that helps predict the likelihood of avalanches like this happening. That's why there are so many avalanche forecasting centers in Canada and the US. You can learn more at www.avalanche.org. Taking a good course can help you prioritize what you should be paying attention to while in the mountains.

In the story, the woman wore a safety device. It seems it save her life.     

You are correct.

[lucky luke]

You are correct.

for the more scientific people: INTERACTION BETWEEN SNOW METAMORPHISM AND CLIMATE: PHYSICAL AND CHEMICAL ASPECT.

For the other; be happy, with have very little snow this year. we won't be able to shovel the roof to verify if the snow is heavier at the begining or at the end of the day!!!

[DWT]

You are correct.

Champ's been setting this moment up for years.

[DGoguen]

I can't decide which is my favorite season here at NEClimbs.
BOLTS or AVALANCHES.

[Admin Al]

I can't decide which is my favorite season here at NEClimbs.
BOLTS or AVALANCHES.

LOL... right on!

[ridgerunner]

Yes but trad or sports avalanche ?

Avalanche (noun). Famous Austrian pick up line when pronounced à la Schwarzenegger. Example : "Hey baby, have a lunch with me ?"

[lucky luke]

I can't decide which is my favorite season here at NEClimbs.
BOLTS or AVALANCHES.

LOL... right on!

I hope that you understand that I am not trying to demonstrate systematically that the other is wrong. it make me sad that the intention is just to make me non-trustable or to disguss other people to climb.

Dman is a guide, he state: " kind of a silly statement. It was rain and/or warm temps that made the snow heavy...[...]... unless by "moisture in the are is absorbed" you mean "when rain hits the snow it is absorbed"..."

I said that when, we take a shower, the humidity of the air condense on a miror. Ice is at zero degree, other wise it is water. When humid air touch the snow, a similar effect happen: humidity condense in the snow. If you have three pounds of snow, and one pound of moisture from condensation, we will have an increase of the weight of the snow to four ponds. Four pounds and the methamorphosis of the light snow flake into a round shape crystal can favorise avalanches.

Who are you going to trust. One say that three pounds of snow with warm temps will give four pounds of water and the other say that three pounds of water plus one pounds of water from condensation of humid air give four pounds?

Because you laught at me, I loose my credibility and people didn't try to understand some point that could save their life, they don't understand why they could be in danger. Many people don't climb because of that. it is not fun.