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Author Topic: Skyline Ridge wallowing 12/18  (Read 5933 times)
Baltoro
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Skyline Ridge wallowing 12/18
« on: 12/18/08, 03:46 PM »

Made a quick trip up the ridge before a friend had to be to work. Lots of snow and it kept on snowing while we were there.

Some suffering was done to re-establish the track as the old track had lots of fresh snow on it. We were aiming for the slope above the lake and a quick ride back the car but were forced to turn back at the lake due to lack of time and extended trail breaking as there was no discernable trail from the main track to the lake.

Skins came off once back to the main track and we were punished everytime we left the skin track as even the steeper open stretches were bottomless and not steep enough to keep up speed. You'd make about three or four turns with smiles and then have to wade out of hip deep snow for ten minutes.

Made me want some Megawatts and a fresh waxing for sure.

It was snowing as we left and continued all the way home.

We didn't dig a pit as we never got to slopes steep enough to slide but judging by pole tests, some brief shoveling at lunch, and hand shear tests it was a pretty continuous layer of fluff before you got to any layers of significant difference.

Tomorrow is supposed to be cold and clear so watch for surface hoar on top of this layer that won't support the snowpack above super-well. Hope some wind comes with the clearing to control hoar development.

Be safe and pray for more snow!
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CookieMonster
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Re: Skyline Ridge wallowing 12/18
« Reply #1 on: 12/18/08, 09:10 PM »

Other than the weather being clear and cold, why do you expect surface hoar formation?
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jeff_s
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Re: Skyline Ridge wallowing 12/18
« Reply #2 on: 12/18/08, 11:08 PM »

Clear cold weather is the typical progenitor of surface hoar, as long as the air is still enough so the layer of water vapor hovering over the snow stays in contact with the very cold snow surface:

"On a cold clear night when the snow surface is cooled by loss of heat to the atmosphere, the air becomes supersaturated with respect to the ice and water vapor condenses on the snowpack to form a...crystalline surface...known as surface hoar. In cold northern latitudes surface hoar will remain unchanged during clear sunny days in midwinter. A thick layer of 1 cm or more can persist in the snow cover for a considerable period of time after its formation. This weak layer acts as a potentially dangerous sliding surface for the snow above."
    --Tony Daffern, "Avalanche Safety for Skiers & Climbers"
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kneel turner
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Re: Skyline Ridge wallowing 12/18
« Reply #3 on: 12/18/08, 11:19 PM »

The snow is so low in H2O content right now (with more forecasted coldness) I can't imagine it developing sufface hoar before Sat/Sun when the next system is suposed to hit.  I'm still "pow drunk" right now, so not really able to scientifically explain this, but if you were in it you know what I'm talkin 'bout Cool.

If I'm way off on this, hit me with some nollej!
« Last Edit: 12/18/08, 11:30 PM by neil turner » Logged

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Baltoro
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Re: Skyline Ridge wallowing 12/18
« Reply #4 on: 12/19/08, 08:04 AM »

Neil
I hear you on how dry the snowpack and I'm not really sure how that'll play out. The good news is people will likely be out today, tomorrow and Sunday to confirm or deny surface hoar formation for us.
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Robert Connor
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Re: Skyline Ridge wallowing 12/18
« Reply #5 on: 12/19/08, 10:42 AM »

Not to make anyone think that hoar won't be an issue where they are, but there are very strong winds forecast in advance of the snow, so I think that in most locations the hoar will be blown clear before it is loaded.
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Jakes_thread
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Re: Skyline Ridge wallowing 12/18
« Reply #6 on: 12/19/08, 11:35 AM »

Agreed, surface hoar usually requires somewhat consolidated snow and more than 36 hours to form. 
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Baltoro
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Re: Skyline Ridge wallowing 12/18
« Reply #7 on: 12/19/08, 11:46 AM »

Good to hear wind will keep the hoar down. Still need to look for it in protected areas.
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CookieMonster
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Re: Skyline Ridge wallowing 12/18
« Reply #8 on: 12/19/08, 10:52 PM »

Thanks for all the replies and good information. I asked Baltoro why he expected surface hoar ( because he'd forecast it in his post ) and clear/cold temperatures aren't enough. So I was curious. Also was curious why his post contained a buried surface hoar forecast.

There are 43 questions in the avalanche exam that deal with surface hoar formation: http://www.scenomics.com/internal/accounts/richardm/avalanche/exam/chapter_03_questions.htm
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jackal
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Re: Skyline Ridge wallowing 12/18
« Reply #9 on: 12/20/08, 07:14 AM »

Cookiemonster, what course does this exam come from?
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Baltoro
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Re: Skyline Ridge wallowing 12/18
« Reply #10 on: 12/20/08, 12:18 PM »

Cookie
First off my avy understanding is limited at best with Level I experience more or less and lots of books and observation. I always lean towards the side of caution and kind of assume "worst-case scenario" conditions until I can prove them wrong by testing and observation.

I said that Friday looked like it could be a good day for surface hoar formation. Hopefully high winds would keep that from happening (and other factors) and we'll no doubt have TR's from others through this weekend that would report surface hoar development or lack there of.

The "buried" surface hoar I guess I was refering to was if surface hoar did develop and we got some snow on top of it, the layer beneath the surface hoar is fairly "bottomless" and wouldn't support much weight.

Regardless of wind affects on surface hoar there could still be protected areas that it could still develop in. I guess all I was trying to communicate is that we should still be on the lookout for layers that could/should develop that could do us harm.

I guess the idea of all of us posting reports and observations is to gain a better understanding of the snow pack through volume of info that we don't have the time to gather ourselves. I like the side-benefit that we can post our observations and have that forecasting validated or critiqued by others. For example, cold and clear seems like good conditions for surface hoar development with lower winds obviously. Cookie had suggested that there's more to it than that so now I know I need to go back to my books and figure what else is a factor as I'm not sure. Thanks.
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Lowell_Skoog
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Re: Skyline Ridge wallowing 12/18
« Reply #11 on: 12/20/08, 05:00 PM »

The snow is so low in H2O content right now (with more forecasted coldness) I can't imagine it developing sufface hoar before Sat/Sun when the next system is suposed to hit. 

Isn't surface hoar the winter equivalent of dew? In other words, it forms because of moisture in the air, not moisture in the snow. I doubt that the water content of the snow has much to do with the formation of surface hoar. If it's like dew, the key factors leading to formation would be relative humidity, radiational cooling, and lack of wind, I think.

If somebody knows better, please post.
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kneel turner
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Re: Skyline Ridge wallowing 12/18
« Reply #12 on: 12/20/08, 07:14 PM »

Lowell, I hear what you're saying, that's why I commented on not being able to explain it scientifically, but the snow was so light it doesn't really have a "surface" to grow hoar.  I think there's something to what jverschuyl posted..consolidated snowpack and 36 hours.  I'd be interested to hear why/how.  My avy books are in storage from a recent move.  I'll have to go dig 'em up. 

Pssst.  Keep it quiet over here.  This threads better than the "Avy discusson".
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T. Eastman
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Re: Skyline Ridge wallowing 12/18
« Reply #13 on: 12/20/08, 07:40 PM »

What was described sounds like typical Colorado conditions.  The ambient ground temps and the cold nights are transforming this "powder" something more sinister that is in the process of having its snowflake structure removed and turned into what will could be best described as ball bearings.  We called this temperature gradient snow (TG) and swore like sailors when it formed some winters.  What falls on top of TG is suspect and a major mid-winter avi cycle was needed to clear the mountains.  Be careful as this is not powder any more and the usual tests for layers used out in the PNW don't (seem to usually)-edit take a base layer like this into account.
« Last Edit: 12/21/08, 12:28 AM by T. Eastman » Logged
Teleskichica
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Re: Skyline Ridge wallowing 12/18
« Reply #14 on: 12/20/08, 09:23 PM »

Be careful as this is not powder any more and the usual tests for layers used out in the PNW don't take a base layer like this into account.

My avy assessment experiences is about as limited as our current base, I have some thoughts on this, but do you have recommendations for assessing conditions from a Rocky Mountain perspective as opposed to our usual PNW perspective?
« Last Edit: 12/20/08, 10:56 PM by Teleskichica » Logged

Livin' high on the cold smoke!
Splitboard Graham
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Re: Skyline Ridge wallowing 12/18
« Reply #15 on: 12/20/08, 10:34 PM »

my limited knowledge and experience would suggest that any buried weak layers that are or already have developed in the current weather patterns will remain weak, dangerous layers unless there is a major warming trend that would penetrate to buried layers without causing wet, untriggered, slides. The forecast looks, however, like some weak layers will be buried under a significant amount of insulating snow in the near term. i'll keep reading the NWAC reports, regardless! peace!
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