Let's talk about avalanches, hazards and snowbiking

May 26, 2020
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We get surface hoar formation a lot, but rarely will it be buried widespread. Typically the sun and wind do a pretty good job of destroying it before it gets buried. Valley bottoms and sheltered lowlands can get buried surface hoar pretty regularly, but then you're out of avalanche terrain in those locations. Although the size of propagating collapses felt when you're on skis can be quite impressive!
 

tribalbc

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We get surface hoar formation a lot, but rarely will it be buried widespread. Typically the sun and wind do a pretty good job of destroying it before it gets buried. Valley bottoms and sheltered lowlands can get buried surface hoar pretty regularly, but then you're out of avalanche terrain in those locations. Although the size of propagating collapses felt when you're on skis can be quite impressive!

Sounds a bit like where I work on the central coast. We get surface hoar less than the south and north coast. I think it has to do with the dry Chilcotin plateau close by.
But the big saviour is prior to the storm the winds pick up and destroy most of it. The sketchy part is the sheltered areas were it doesn't get destroyed usually are the best skiing as well. That and our heli skiing tenure is the size of the Swiss Alps so massive variability.
 
May 26, 2020
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With climate change, our Intermountain snowpack has trended more towards Continental in the last few years...

Persistent and Deep slab instabilities have become the norm... bummer.
 

tribalbc

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Interesting.
Right now I am looking at the most snow I have seen for this time of year since 98, which was a record year. Heavy snow throughout the forecast continues. We could be looking at a record season...
 

needpowder

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One thing I didn't mention for Maritime areas (as well as Continental areas), is they can get buried surface hoar, which is a type of Persistent Slab problem, and can be quite deadly.

Surface Hoar (often called hoar frost) forms on the snow surface when you have cold, clear nights. The feathery crystals can form a weak layer when they get buried intact by new snow. By intact I mean standing upright. The analogy is "bricks on chips" - if you imagine balancing a brick on a group of upright potato chips, the chips can do a pretty good job hiding the brick upright, but if you were to add more weight, like that of a rider, the chips collapse and now you've got an avalanche. Buried surface hoar can be tricky because it is difficult to know where it is buried intact in the terrain; it may be widespread, it may be specific, or it may only be isolated. Around here in central Idaho, we typically don't get a buried surface hoar event that is widespread (meaning on all slopes at all elevations). Often times the sun on solar aspects and the wind in exposed terrain destroys the surface hoar before it gets buried by the next storm. But in places like coastal BC or Alaska, they can sometimes get a clearing after a storm with a cold, clear night where surface hoar forms then another storm that rolls in on the heals of the first that buries it, and now you've got Persistent Slab of buried surface hoar that can be pretty f'n spooky...
The most spooked I have ever been in avalanche terrain was a buried surface hoar layer in Haines Alaska about 15 years ago. We showed up in Haines and the layer was buried about a foot deep. Not terribly unmanageable. Then the weather comes, couple down days lots of drinking blah blah blah. Bluebird! We are flying again only now the layer is about 3 feet deep. Couple close calls and we call it a day. Weather moves in for a couple days, sun pops out and we are at it again. Only now the surface whore is buried about 5 feet deep. Still just as reactive. Couple close calls on what we considered mini golf slopes and we call it a trip and head home. I will never forget watching hundreds of tons of snow get swallowed by a bergschrund. Talk about unsurvivable.
 

tribalbc

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The most spooked I have ever been in avalanche terrain was a buried surface hoar layer in Haines Alaska about 15 years ago. We showed up in Haines and the layer was buried about a foot deep. Not terribly unmanageable. Then the weather comes, couple down days lots of drinking blah blah blah. Bluebird! We are flying again only now the layer is about 3 feet deep. Couple close calls and we call it a day. Weather moves in for a couple days, sun pops out and we are at it again. Only now the surface whore is buried about 5 feet deep. Still just as reactive. Couple close calls on what we considered mini golf slopes and we call it a trip and head home. I will never forget watching hundreds of tons of snow get swallowed by a bergschrund. Talk about unsurvivable.

The worst thing about surface hoar is the remote triggering.
I have seen it so bad you can only safely ski flat glaciers and you are still triggering slopes 2km away. Gives a whole new outlook on overhead hazard.
 
Nov 26, 2007
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Chinook Pass, Wa
Excellent discussion fellas!!! I had an extremely close call 2 years ago that really opened my eyes, but not right away. Since the incident I've had a lot of time to THINK about it and really understand what went wrong and why.

A buddy and I were riding sleds on a blue bird day. We were in about 18" of new pow over about 4' of old hard snow. We had been riding all day, slaying the pow and having a blast. We decided that we would cut across a huge north facing ridge towards the west to come back down another ridge. We were sidehilling and climbing up and down the slope as we worked our way across the 2 mile long ridge. I was in the lead and I came to a small ridge coming off of the slope running north. I pinned it and ran up the little ridge and busted thru a sweet 4' cornice, caught some air and then stopped at the landing to watch my buddy bust the cornice. This was the smartest decision I made that day. I sat there with my sled running watching as my buddy took a higher line (60-70'). Just as he got to the cornice, the whole lee side of the little ridge broke loose. The slab was 100' wide, by about 50' high and about 2' deep. I've been in emergency response for well over 20 years and instantly saw and understood what was happening. The first thought in my head was "I have to watch him until everything stops moving" I watched him and his sled tumble and slide down the hill about 100 yards. If I hadn't sat and watched the whole slide I wouldn't have had any idea where to begin searching for him. (no beacons or probes in those days, have them now!) When I saw the slide stop, I immediately went to the PLS. and started yelling as loud as I could that I was there and I was going to get him out. He had only 1 finger tip (about a half inch of glove) sticking out of the snow. I grabbed my shovel and dug and yelled as fast and as loud as I could. He ended up being upside down facing down hill.

After I got him out, we sat there in silence just breathing holding each other for about 10 min. He told me that he knew instantly when the slab broke that he was going to die, but when he heard my voice thru the crushing blackness he knew he would be okay. From the time the slide stopped and I started moving until the time I got his face dug out so he could breath was probably 1 min to 1 min 30 sec. He helmet was completely packed with snow.

I think about that day every time I go in the backcountry in snow and try to see things differently and make better choices. I no longer care about being the highest on the hill or catch the most air off of the cornice...now I think about myself and all of my buddies having a great day and going home to our families at the end of the day.

Thanks for the great info fellas, please keep it coming!!
 

CATSLEDMAN1

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The beauty of discovering sno bikes 9 years ago was being able to ride the trails in Western Mt that have been just summer rides.
We tried a little of that on the sleds over the years, but sleds work best out on open slopes. Sleds work best in Avalanche terrain sad to say. Our riding area has a lot of timberline canyons/ridges/cirque's/beautiful cornices windblown ridges where you can view 8 or 9 major mtn ranges. Glad to say after spending many winter years there, haven't even been temped to ride up those canyons on our bikes. 10 years of going the other way in complete joy. Its my way to mitigate Avalanche danger. I carry a chainsaw more than I carry a full Avalanche pack. Times they do change.
 

tribalbc

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The beauty of discovering sno bikes 9 years ago was being able to ride the trails in Western Mt that have been just summer rides.
We tried a little of that on the sleds over the years, but sleds work best out on open slopes. Sleds work best in Avalanche terrain sad to say. Our riding area has a lot of timberline canyons/ridges/cirque's/beautiful cornices windblown ridges where you can view 8 or 9 major mtn ranges. Glad to say after spending many winter years there, haven't even been temped to ride up those canyons on our bikes. 10 years of going the other way in complete joy. Its my way to mitigate Avalanche danger. I carry a chainsaw more than I carry a full Avalanche pack. Times they do change.

As you say this is the beauty of snowbikes. We can have fun all day long in non avalanche terrain, with sleds not so much.
Again it all comes down to terrain. When conditions permit I love ripping turns down big alpine lines like skiing. But when the avalanche conditions aren't compatible I am more than happy to rip around in non avalanche terrain.
I would really like to try going snowbiking at one of our major summer riding areas. Lots of meadows, good tree spacing and no avalanche paths, though there is terrain steep enough that could get you in trouble. Haven't got around to it as it is a couple hours from my house were as the areas I ride in the winter are 5 to 45 minutes away. Maybe sometime this winter....
 
Feb 4, 2011
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There was a VERY close call in northern Utah recently. The "Avalanche Problem" was a "Persistent Weak Layer" of sugary faceted snow near the ground. This collapsed under the layers of snow on top of it when it was disturbed by the rider. This is the most dangerous situation for riders in the Intermountain and Continental snowpack regions. It kills the most people out of any of the avalanche problems. I'll extrapolate a bit more when I get time.

Here's the link to the avalanche report: https://utahavalanchecenter.org/avalanche/57365

And a video:
 

simple

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Wow, reading that report, he really almost died. 15 minutes under feet of snow is normally death. Thanks for sharing that incident. Be safe out there with this next storm. The snowpack is garbage this year.
 

tribalbc

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There was a VERY close call in northern Utah recently. The "Avalanche Problem" was a "Persistent Weak Layer" of sugary faceted snow near the ground. This collapsed under the layers of snow on top of it when it was disturbed by the rider. This is the most dangerous situation for riders in the Intermountain and Continental snowpack regions. It kills the most people out of any of the avalanche problems. I'll extrapolate a bit more when I get time.

Here's the link to the avalanche report: https://utahavalanchecenter.org/avalanche/57365

And a video:


No shortage of terrain traps there, happy that had a good outcome. Sounds like it was minutes away from not being so good. That many trees and the chances of trauma are so high as well.

This is a good little push to get this thread going again. Been kinda slacking and putting it off.
 
Jan 14, 2004
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Once again a "treed/safe area" event. I have been lulling myself into a false sense of security saying we only ride in the trees therefore its got to be safe. Clearly this season the snowpack is revealing what can actually happen virtually anywhere. Riding under those types of features has always given me the hee bee gee's but I still have done it, LOTS, obviously too much. I need to pay more attention to my route selection and make the effort to go around some of those "Easy Crossings" and avoid having bad things above me.

M5
 

tribalbc

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Jan 26, 2019
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So not really an avalanche problem but reading that report and seeing them talk about airbags "floating" you to the surface, I thought I would talk about how airbags work.
An airbag does not "float" you to the surface like a pfd, it's all about particle size. Simple analogy, take a jar full of all different size rocks and shake it around. What happens? All the small particles end up on the bottom and the larger ones on top. This is the same premise an airbag functions on.
So if you are in an avalanche with your airbag deployed and get taken for a long ride chances are very high you will end up on top.
The weakness of an airbag is that if there is not enough mechanical motion than it will do nothing. Examples.

You went for that big ride, ended up on top but stuck and then the secondary wave comes over you.

You are at the bottom of a slope and an avalanche hits from above.

There are obstacles, trees, etc on the slope that hang you up on the way down.

Terrain trap at the bottom. Even if you are on top reaching the bottom, unless you are at the tail of the slide that leftover snow has no where to go but on top of you.

Airbags are awesome tools just beware they have some limitations.
 
May 26, 2020
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There was a VERY close call in northern Utah recently. The "Avalanche Problem" was a "Persistent Weak Layer" of sugary faceted snow near the ground. This collapsed under the layers of snow on top of it when it was disturbed by the rider. This is the most dangerous situation for riders in the Intermountain and Continental snowpack regions. It kills the most people out of any of the avalanche problems. I'll extrapolate a bit more when I get time.

Here's the link to the avalanche report: https://utahavalanchecenter.org/avalanche/57365

And a video:
Thanks for sharing... scary stuff!

Remember, it's not always the slopes you're on, but can also be the slopes you're underneath. This is especially true this year, as most western states are dealing with a Persistent Avalanche Problem and Remote Triggers are real and happening.

How do you know if you are clear of overhead hazard? Measuring your Alpha Angles is a relatively quick and easy way to get an idea if you are exposed to overhead hazard while ripping around the flats. Alpha angles can vary depending on the type of avalanche problem you're dealing with, but if you just remember 20 degrees or less, that will keep safe from nearly all overhead avalanche hazards.

How do you measure Alpha Angles? There are sever tools you can use such as a compass with an inclinometer or a specific slope angle tool like BCA sells. Personally, I like to use my phone. On my iPhone, in the Utilities App I select the Level function, then holding my phone on edge I sight down the long edge from my position to either the top of the peak/ridge/bowl or where I think the start zone of an avalanche might be. This will give me a number on the screen and if I'm seeing anything greater than 20* then I know that I'm potentially exposed to an avalanche on that slope.

This doesn't have to be cumbersome and take a lot time. When I'm out for a day with a group, we have decided ahead of time what type of terrain is appropriate for the current conditions (non avalanche, simple, challenging, or complex). We've also picked a few spots to stop, regroup and reassess conditions and check in with each rider. Braaaping into a new zone is a good time to do this. If you're dealing with a Persistent Slab problem and the local avalanche bulletin is warming of remote triggers, I'll pull out my phone, shoot a couple alpha angles and set some boundaries on where we think it's safe to ride and terrain that should be avoided.

Read the local forecast. Know what to look for. Know what to avoid. Communicate with your group. Play safe and come home at the end of the day! I'm huge proponent of avalanche education, not only because I'm an instructor, but also because I believe that you'll never achieve your potential as a rider if you know nothing about winter mountains and avalanches.

If you're near Central Idaho I've got another Motorized Level 1 Course coming up Feb 5-7.

We've got a storm rolling into our zone this week (finally!!!). We're currently dealing with a stubborn Persistent Slab problem with a buried facet layer anywhere from 40-80cm down from the snow surface. We've also noted widespread surface hoar on nearly all aspects and elevations. The potential is there. Things could get pretty real here by the end of the week if we receive the 1.5-2' of snow they are forecasting!
 
Dec 30, 2010
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Rode north of Sandpoint on Saturday and other than the really annoying crust layer that made things pretty miserable we noticed a lot of frost hoar above 5000ft. Under most of the crust was a lot of sugary snow in almost every aspect that we rode. With the coming storms over the next week it might be a while before the snowpack is stable.
 

simple

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I wish there was a setting on Cal Topo for Alpha angles and not just slope angles.
It isn't that easy to measure as it is based subjective parameters. Not measurable topographic features. Most scientists and experts just use conservative values to get rough estimates. Quantitative vs qualitative as a lot of avalanche science is. That is a difficult mindset for many to reckon with as they want hard numbers on what is safe or not. We commonly answer with "it depends"
 
May 26, 2020
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Slope angle shading on caltopo is not 100% accurate and has led to an accident resulting in a fatality before. It's a great tool, but threading the needle between shaded spots is not how it should be used. Conversely, it's also easy to apply slope angle shading to a zone prior to heading out, knowing you don't want to get on anything greater than 35*, and feel like the sky is falling because everything is shaded red. What caltopo doesn't take into consideration is slope shape (convex, concave, bowl, ridge, etc); and vegetation - i.e. are there enough trees to be anchoring / disrupting the slab/weak layer to where it's not a problem.

Yes, caltopo is an awesome tool, especially using the slope shading feature, but I find it's also helpful to know how to measure slope and alpha angles on the fly.

How many sledding videos have you seen where the group is watching someone in their party tear up a slope when the whole thing rips, comes down and takes out the party watching/filming? Reducing the number of victims in a situation like that is a pretty easy thing to do...
 
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