"The Fine Line" podcast is excellent! It is from Teton County's Search and Rescue and is very enlightening!
Let's talk about avalanches, hazards and snowbiking
- Thread starter tribalbc
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Agreed. I am a long time subscriber.
Those pics from Pemberton are an eye opener, that feature looks very unassuming. We've all ridden through lots of those. If you haven't looked at the pictures, do its worth your time.
M5
M5
As M5 said the terrain the accident happened on looks very unassuming. The hazard was only rated moderate, it was a cool sunny day with no wind. The surface snow had no wind effect and conditions seemed just about perfect.
Were there any signs they missed that could have changed their decision making?
There were two. The surface hoar buried a few storms before and wind transport.
We have touched on wind transport before but let's go a little more in depth.
Think of wind traveling through the mountains like whitewater through a river. Any irregularities in terrain shape will cause little eddie's in the wind that will load the lee side.
So I'm sure most understand what happens when the wind goes straight up one side of the mountain. It strips the snow as it accelerates up and deposits the snow in the eddie on the other side. Knowing the typical prevailing winds during storms for your mountain range, and even better the winds that have accompanied the previous storms
is a huge plus.
We typically think of south faces as the windward side or side the wind blows up. North faces are called the leeward side and they get the eddie's and resulting snow loading.
I think most get this concept pretty easily. But now what about east and west exposures? This is where crossloading comes into play and it is a much more complex and dangerous problem. Any bumps, gullies, rocks or trees on a crossloaded feature are going to have snow stripped on the windward side and loaded on the lee side. This not only has the danger of loaded pockets but also makes adjacent shallow spots where it is easier to trigger a slide (more on that later)
Crossloading can happen on any exposure but I used east and west as they are more typical.
Pretty obvious crossloading
A bit more subtle. Picture where the wind would strip and then deposit snow as it goes across this slope.
How this pertains to the accident. There was a surface hoar layer that was buried by several storms with strong to extreme southerly winds. The area where the accident happened had two negatives here for that. With local knowledge you know it is a classic place for a lot of surface hoar, even when sporadic in other areas. It is also west facing with very undulating terrain making it a bad area for crossloading.
Were there any signs they missed that could have changed their decision making?
There were two. The surface hoar buried a few storms before and wind transport.
We have touched on wind transport before but let's go a little more in depth.
Think of wind traveling through the mountains like whitewater through a river. Any irregularities in terrain shape will cause little eddie's in the wind that will load the lee side.
So I'm sure most understand what happens when the wind goes straight up one side of the mountain. It strips the snow as it accelerates up and deposits the snow in the eddie on the other side. Knowing the typical prevailing winds during storms for your mountain range, and even better the winds that have accompanied the previous storms
is a huge plus.
We typically think of south faces as the windward side or side the wind blows up. North faces are called the leeward side and they get the eddie's and resulting snow loading.
I think most get this concept pretty easily. But now what about east and west exposures? This is where crossloading comes into play and it is a much more complex and dangerous problem. Any bumps, gullies, rocks or trees on a crossloaded feature are going to have snow stripped on the windward side and loaded on the lee side. This not only has the danger of loaded pockets but also makes adjacent shallow spots where it is easier to trigger a slide (more on that later)
Crossloading can happen on any exposure but I used east and west as they are more typical.
Pretty obvious crossloading
A bit more subtle. Picture where the wind would strip and then deposit snow as it goes across this slope.
How this pertains to the accident. There was a surface hoar layer that was buried by several storms with strong to extreme southerly winds. The area where the accident happened had two negatives here for that. With local knowledge you know it is a classic place for a lot of surface hoar, even when sporadic in other areas. It is also west facing with very undulating terrain making it a bad area for crossloading.
Here's a pic of mine of some complex alpine terrain for crossloading. You can see the stripping on the windward sides and the loading on the leeward.
While I am looking through my photos a good example of an avalanche on a unsupported feature. If you notice on the right of the picture the slope is just as steep and has the same snowpack but it didn't release because it is supported.
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Classic release on the unsupported convexity
Good stuff tribalbc. Thanks for starting this thread.
Like you I have worked professionally in avalanche terrain for 20+ years: 7 years of ski patrol with avalanche mitigation and 20 years of ski and snowboard guiding around the world. But I've been riding motorcycles (dirt and street) for almost 40 years and have had a handful of snowmobiles over the years. This will be my first year on a snowbike.
Motorized users need to address what's missing in their kit, and most of the time it's not equipment... it's education. The hiccup is that up until now, avalanche courses were created by skiers, for skiers. Yeah some info was relevant, but honestly, to pull out a pencil, notebook and checklist every time you changed aspect was clunky to say the least.
Thankfully my friend Travis at the Sierra Avalanche Center has developed a level 1 curriculum specific to motorized users. Travis is a forecaster, ski guide, avalanche educator, solid dirt biker and bad ass sledder. His Daily Flow approach makes sense to motorized users and doesn't interfere with a day of riding in the mountains. In fact it should become an integral part of your day of riding in the mountains.
We've adopted Travis's curriculum and the Daily Flow and will be teaching Level 1 avalanche courses here in central Idaho this year with it.
Check out this short video on the Daily Flow:
Like you I have worked professionally in avalanche terrain for 20+ years: 7 years of ski patrol with avalanche mitigation and 20 years of ski and snowboard guiding around the world. But I've been riding motorcycles (dirt and street) for almost 40 years and have had a handful of snowmobiles over the years. This will be my first year on a snowbike.
Motorized users need to address what's missing in their kit, and most of the time it's not equipment... it's education. The hiccup is that up until now, avalanche courses were created by skiers, for skiers. Yeah some info was relevant, but honestly, to pull out a pencil, notebook and checklist every time you changed aspect was clunky to say the least.
Thankfully my friend Travis at the Sierra Avalanche Center has developed a level 1 curriculum specific to motorized users. Travis is a forecaster, ski guide, avalanche educator, solid dirt biker and bad ass sledder. His Daily Flow approach makes sense to motorized users and doesn't interfere with a day of riding in the mountains. In fact it should become an integral part of your day of riding in the mountains.
We've adopted Travis's curriculum and the Daily Flow and will be teaching Level 1 avalanche courses here in central Idaho this year with it.
Check out this short video on the Daily Flow:
Sounds like we might know some of the same people. Many moons ago in the early years of ski and snowboard movies I guided for companies like TGR, Matchstick, Standard films, etc. Was great in those early days, we only went were no one had been before, great exploration.
Like you I grew up with dirt bikes, raced many years of off road. Always owned a sled since the early 90's, loved where it got me, but never grooved on the feel that much.
You are going to love snowbiking. Feels just like snowboarding ripping big pow turns. I literally like it better than skiing these days because even if the terrain becomes a little mellow for that turn, you have that throttle to twist.
We literally shred the same lines downhill as you would want to hit on skis.
For some reason the volume won't work on that video for me.
Yeah, bet we could have a fun time name dropping and sipping a few cold ones after a ride...
I got exposed to snowbiking in a big way back in 2016 when I was hired for snow safety for a local Redbull Timbersled shoot. Reagan Sieg and Brock Hoyer blew our frickin minds each day of the shoot. Ronnie was getting schooled but figuring it out pretty quick, especially having never been on snow. Reagan let me braaap around a bit on his bike a couple times. I was in ski boots but immediately saw/felt the potential...
Here's the link for the Daily Flow, maybe by going to website you'll get the audio...
I got exposed to snowbiking in a big way back in 2016 when I was hired for snow safety for a local Redbull Timbersled shoot. Reagan Sieg and Brock Hoyer blew our frickin minds each day of the shoot. Ronnie was getting schooled but figuring it out pretty quick, especially having never been on snow. Reagan let me braaap around a bit on his bike a couple times. I was in ski boots but immediately saw/felt the potential...
Here's the link for the Daily Flow, maybe by going to website you'll get the audio...
Really enjoying this conversation. Much more advanced than what we teach to pre- level 1 folks here so it is enjoyable to have experienced dialogue. With recent snowbike incidents it is clear that the machines are very advanced beyond the user knowledge. We had a tragedy in the Flat Tops that was perplexing and seemed to enlighten part of the community about the importance of avalanche education. Lots more people getting into it in even the 3 years since but our classrooms have been full with eager learners.
Thanks for the thread, needs to be said. Avalanche danger is like wearing a mask these days, some folks will not believe it until they die, so sad.
I like your terrain terrain terrain matra. Here in Western Montana our snow comes from coastal storms, almost 100% west to east wind activity, snowy days rainy days sunny days, same wind patterns. As walk or ride the back country on my dirt bike I see at the Alpine levels nearly all the mtn cirques, mtn little lakes, ice cut ridge lines a result of this East side snow loading and Avalanche activity for hundreds of thousands of years.
So when you enter this country in winter.......no trees, there's reason. Constant avalanche activity denuding the slopes........or maybe just a boulder scree slope, I know, I been riding the same area for 50 years. NOW, to slow down some of my younger friends who think I am the worlds biggest fraidy cat, the guy who is always saying, hey let go this way. They kid me about always taking the easy way, less challenging course, but its making the day a round trip that makes me happy. Studying an area with some guys last winter on their new Arctic Cat single rail big track sleds, I suggested they cross the creek and go around, Bill E said, MIke, you're always afraid of dying in an Avalanche, I said no, I am afraid at my advanced age I am not in good enough physical shape to save / rescue my riding partners, and then have to live with that.
I like your terrain terrain terrain matra. Here in Western Montana our snow comes from coastal storms, almost 100% west to east wind activity, snowy days rainy days sunny days, same wind patterns. As walk or ride the back country on my dirt bike I see at the Alpine levels nearly all the mtn cirques, mtn little lakes, ice cut ridge lines a result of this East side snow loading and Avalanche activity for hundreds of thousands of years.
So when you enter this country in winter.......no trees, there's reason. Constant avalanche activity denuding the slopes........or maybe just a boulder scree slope, I know, I been riding the same area for 50 years. NOW, to slow down some of my younger friends who think I am the worlds biggest fraidy cat, the guy who is always saying, hey let go this way. They kid me about always taking the easy way, less challenging course, but its making the day a round trip that makes me happy. Studying an area with some guys last winter on their new Arctic Cat single rail big track sleds, I suggested they cross the creek and go around, Bill E said, MIke, you're always afraid of dying in an Avalanche, I said no, I am afraid at my advanced age I am not in good enough physical shape to save / rescue my riding partners, and then have to live with that.
I think too often the machine and ability is looked at as the only limiting factors and not the conditions/ terrain.
Like so many things in life we can only help those that are willing to accept help.
There is an old saying in the mountain guiding business.
"There are old guides and there are bold guides, but there are no old bold guides"
So I definitely have lots more to talk about here and it will be coming.
But I would also like to hear what you guys want talked about and any questions. Please feel free to participate.
But I would also like to hear what you guys want talked about and any questions. Please feel free to participate.
Could you touch on the use of Snotel data to help evaluate an area?
I was in an avalanche awareness presentation last year and the guy said he watched Snotel data all through the fall to help evaluate the condition of base layers. Are there patterns or scenarios that may indicate a dangerous base?
Also, I live in an area that isn't covered by avalanche forecasters. I read the reports for areas East and west of me to get a general idea of what similar ranges are seeing. Is this doing me any good or just giving me false confidence\anxiety?
I was in an avalanche awareness presentation last year and the guy said he watched Snotel data all through the fall to help evaluate the condition of base layers. Are there patterns or scenarios that may indicate a dangerous base?
Also, I live in an area that isn't covered by avalanche forecasters. I read the reports for areas East and west of me to get a general idea of what similar ranges are seeing. Is this doing me any good or just giving me false confidence\anxiety?
That is strange. Snotel sites are usually in a flat spot that doesn't get hammered by wind. I can't see how that can be extrapolated into avy data when terrain slope, aspect, and loading direction are such important parameters to risk.
Snotel sites are for water resource management.
Evaluating fall snowfall is a good idea. If early snow occurs and then followed by dry spells that early snow turns to facets (sugar) on north and northeast aspects. South aspects generally melt out. Those slopes with that sugar snow then get a slab built on them in the winter. It may take a while for the poor base to go away. This is especially common in continental area like Colorado. So yes, looking at snowtel can tell you where the snow is but considering they aren't on a slope or aspect takes away an important data point.
Snotel sites are for water resource management.
Evaluating fall snowfall is a good idea. If early snow occurs and then followed by dry spells that early snow turns to facets (sugar) on north and northeast aspects. South aspects generally melt out. Those slopes with that sugar snow then get a slab built on them in the winter. It may take a while for the poor base to go away. This is especially common in continental area like Colorado. So yes, looking at snowtel can tell you where the snow is but considering they aren't on a slope or aspect takes away an important data point.
Snotel data can be very useful for precipitation totals and temperatures. Much like Simple said, if you monitor snotel sites, you can get a general idea of what you expect the snowpack to look like when you get in the field. There are infinite scenarios that could play out over the course of a season, but Simple described one that could lead to depth hoar and basal facets (a weak layer at the base).
One thing to remember is that the layering of the snowpack and the avalanche problems you may encounter is directly related to the weather history of a given area. If you live in a coastal area that receives consistent snowfall throughout the season, you will see very few layers in the snowpack, and typically deal with Wind Slabs and Storm Slabs until warming temps in the spring where you might find Wet Loose and Glide avalanches. This is called a Maritime snowpack, as it's close to ocean. The other extreme is a Continental snowpack, where you typically get a storm, then an interval of dry weather before the next storm. Colorado is a great example of this. Like Simple explained, it is during the intervals between storms that weak layers are created. Cold temps (less than 20*f at night) and clear skies leads to a metamorphic process in the surface snow that creates angular snow grains, called facets, or sugar snow. These facets don't bond together at all and tend to persist over time in the snowpack. Then when the next storm arrives new snow falls on the facets, creating a slab (cohesive snow) over a weak layer (less cohesive snow). This type of avalanche problem is called a Persistent Slab, and if it's deep in the snowpack (more than 1m or 3') than it is called a Deep Slab. Areas like CO not only deal with Wind and Storm Slabs, but also Persistent and Deep Slabs.
So, by monitoring a Snotel site, you can formulate a picture of what the layering in the snowpack looks like from the comfort of your home. For example, say it snowed at X location in early Nov, then didn't snow for 3 weeks with temps in the teens at night and highs in the 20s, then it dumped 2' of snow over Thanksgiving with temps in the 20s and low 30s, I would expect to find a slab of cohesive snow over a weak layer of less cohesive snow - on other words, a Persistent Slab.
Finally, like Simple alluded to, Snotel sights are located in protected areas and do not have any wind data. This is important to remember as you paint a picture of conditions in your head. This doesn't mean that the Snotel data is useless, it just means that it won't give you the entire picture. But it will give a good base understanding of what to expect. If there was significant wind (> 20mph) for sustained periods (> 1hr) you should expect to to have transported snow. Wind will transport snow from the windward side to the lee side, and this can happen up to 10x faster than snow can fall out of the sky. This transported snow can create pillows (soft piles of snow) and wind slabs (hard or firm snow overlaying weaker, less cohesive snow) along ridge tops, and terrain features exposed to the wind. These may be sensitive to a riders weight and may fracture and propagate into an avalanche. So, if I were headed into an area that had no forecast, but did have a Snowtel site or 2, I'd look up the weather history and get a general idea of what the layering in the snowpack would look like before heading out. Once out there, I would look for signs of wind effect in the terrain (scoured ridge tops, sculpted snow, etc) and test what pillows and wind slabs I found on non-consequential slopes. If the Snotel data led me to believe I might find a Persistent Slab in the area, then I'd probably also dig a quick pit and do a Compression Test as well as an Extended Column Test to get a baseline for how the snowpack might react to a riders weight. If the Snotel data pointed more towards a Storm Slab (1' or more of snow in the last 24hrs) I'd probably do a couple hand pits but mostly ride across the tops of a couple small non-consequential slopes (test slopes) to see how the new load reacts to my weight.
That was a long down out explanation, but I hope you found it helpful.
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...
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...
ProAlpine did an excellent job of laying that out I will just expand a bit.
Snotels (first time I have heard this term) or snow pillows in Canada give us good data to use. That they are in a flat spot and don't give winds isn't an issue for what you want from them. In fact when we make a study plot for monitoring snow one of the criteria is it is less than 10 degrees and protected from wind. This way we know the actual snowfall amounts, wind is factored in later.
A good way to use these stations you have to the west and east of you would be to look at the data after a fresh snowfall and then measure the actual amount of new snow in your area. Now you have a baseline of what that data means.
Do you guys in the states not have access to highway weather stations for avalanche control? These would have better data for you.
The big thing to remember is snow is an ever changing substance. It is either getting stronger, rounding, or it is getting weaker, faceting. When you have a deep snowpack and warmer air temps the snow will round. When you have a shallow snowpack and cold temps the snowpack will facet and eventually form depth hoar.
Rounds pack together nicely. Facets which are square shaped will not hold together and have the texture of sugar. Facets on there own are not an issue. They will fall away but only where they have been disturbed and will not propagate into a large avalanche. But now put a stiff layer of snow over them and you have the recipe for avalanches.
So big red flags are long cold dry periods followed by fresh snow. Immediately after a storm if there was no wind you may see no activity as the snow above is uncohesive. But add some wind or sun to the mix and now you have a stiff slab capable of big avalanche propagation. Continental snowpacks generally have this week layer near the ground the entire season just waiting for that tipping point or the right trigger.
Could go on forever on this subject but I will stop there for now.
ProAlpine I am surprised surface hoar is not a huge issue for you in Idaho. It can be an issue here on the coast for sure but nothing like the interior of BC. Especially the Columbia River valley with all that moisture it's a surface hoar farm.
Snotels (first time I have heard this term) or snow pillows in Canada give us good data to use. That they are in a flat spot and don't give winds isn't an issue for what you want from them. In fact when we make a study plot for monitoring snow one of the criteria is it is less than 10 degrees and protected from wind. This way we know the actual snowfall amounts, wind is factored in later.
A good way to use these stations you have to the west and east of you would be to look at the data after a fresh snowfall and then measure the actual amount of new snow in your area. Now you have a baseline of what that data means.
Do you guys in the states not have access to highway weather stations for avalanche control? These would have better data for you.
The big thing to remember is snow is an ever changing substance. It is either getting stronger, rounding, or it is getting weaker, faceting. When you have a deep snowpack and warmer air temps the snow will round. When you have a shallow snowpack and cold temps the snowpack will facet and eventually form depth hoar.
Rounds pack together nicely. Facets which are square shaped will not hold together and have the texture of sugar. Facets on there own are not an issue. They will fall away but only where they have been disturbed and will not propagate into a large avalanche. But now put a stiff layer of snow over them and you have the recipe for avalanches.
So big red flags are long cold dry periods followed by fresh snow. Immediately after a storm if there was no wind you may see no activity as the snow above is uncohesive. But add some wind or sun to the mix and now you have a stiff slab capable of big avalanche propagation. Continental snowpacks generally have this week layer near the ground the entire season just waiting for that tipping point or the right trigger.
Could go on forever on this subject but I will stop there for now.
ProAlpine I am surprised surface hoar is not a huge issue for you in Idaho. It can be an issue here on the coast for sure but nothing like the interior of BC. Especially the Columbia River valley with all that moisture it's a surface hoar farm.
