kklassen
New member
My name is Karl Klassen. I am the Public Avalanche Bulletins Manager for the Canadian Avalanche Centre in Revelstoke. I have 32 seasons experience as an avalanche professional and mountain guide. I have worked in most aspects of avalanche work in many mountain ranges around the world. I am married with an almost-nine year old son. Our family regularly goes into the mountains, including the backcountry, both in winter and in summer.
On behalf of the CAC and all its staff as well as from my family and I, I extend sincere condolences and sympathies to the families and friends of victims of the recent fatal avalanches. In addition we send our hopes for a speedy and full recovery to those who were injured.
Following is an excerpt from a paper posted on the CAC website that discusses the current avalanche problems in many areas of the BC interior mountains. The advice contained here is applicable to most areas of the Columbia Mountains and North Rocky Mountains from MacKenzie in the North to the US border in the south and between Prince George, Williams Lake, Kamloops, Kelowna and Osoyoos on the west and Chetwynd/Tumbler Rige, Valemount, Golden, and Cranbrook on the east. In addition, last I heard, the South Chilcotin Mountains north of Pemberton also have a persistent weak layer (PWL) problem.
Before I go on, I must stress there is no 100% guarantee of safety in the mountains. You could be caught in an avalanche, injured, or killed even if you follow every piece of advice in this discussion and “do everything right.” That said, avalanche accidents are preventable—it’s up to you to get the training, information, and appropriate equipment to properly manage your risk if you choose to go into the mountains.
My intention is not to scare people out of going into the mountains. It is possible to manage risk, maintain reasonable margins of safety, and make informed decisions in the conditions we are currently experiencing. But my personal approach to a snowpack like this one is very different than when there are fewer or no PWLs involved. Local knowledge of the snowpack and experience with similar conditions are critical components in managing risk this winter. A high level of training and experience are required to tackle large pieces of terrain in a PWL winter.
Persistent weak layers like those currently in the snowpack are among the most difficult of all avalanche problems to assess, predict, and manage. Even with extensive training and over 30 years professional experience, I struggle with the current combination of “low probability-low frequency-high consequence.” That is, it’s often difficult to trigger a deeply buried instability and the number of avalanches you see is low, but the consequences if caught in a deep slab avalanche are very serious due to the size and mass of the slide. The answer lies in making decisions based on what you know about a slope, its history of avalanche activity over the season, slope use patterns (e.g. compaction), and/or stabilization (avalanche control) measures. In the absence of such knowledge or without the training to properly assess the information that is available to you, the only reasonable way to manage your risk is by leaving a wide safety margin wherever a PWL is known or suspected.
Terrain Choices and Travel Techniques
PWLs are associated with high uncertainty and low confidence. With PWLs I don’t ask: “Will it slide?” I do ask: “When it slides, what will happen to me or my partners?” This approach leads to greater margins for error, which in my opinion, is the best way to manage risk at times and places where confidence is low. With PWLs, I am extremely careful in choosing what terrain I use, when I go there, and how I manage my groups. Here are some general tips for managing risk at any time and some specific ideas for dealing with PWLs in general and the specific PWL problems we face this season:
• DO NOT stop, regroup, or park in avalanche paths.
• DO stop, regroup, or park only in safe areas where avalanches will not start or run through/over:
o High points.
o Ridges above start zones.
o Dense timber well away from the track or runout zone.
• Eliminate or minimize exposure to terrain traps, such as:
o Depressions
o Gullies
o Creek beds
o Sudden transitions from steep to flat (lakeshores, benches, road cuts, etc.).
o Slopes where an avalanche might carry you:
Over a cliff.
Into trees.
Against obstructions such as rocks or boulders.
• Take a more conservative overall approach in areas where this year’s PWLs are more prevalent. Find out where they are a problem and current conditions by checking the information at: Bulletins : Bulletins : Canadian Avalanche Centre : avalanche.ca.
• If you must travel in or through start zones or tracks, go one at a time from safe spot to safe spot.
• Go one at a time or spread out when travelling in or through avalanche runout zones.
• Take a more conservative approach at Treeline and Alpine elevations in the current conditions.
• Take a more conservative approach on shaded aspects in this year’s condition. If you are riding good powder, you are in the bulls eye for triggering a PWL avalanche.
• Avoid slopes that have rocks and scattered trees sticking out of the snow.
• Avoid unsupported terrain features (that is pronounced convexities or rolls).
• Stay on low angle slopes that are less than 30o incline. While this is a general rule and is often quoted, it may be of limited use this year as we are seeing avalanches running on slopes as low as 20 degrees. I suggest an very conservative approach to terrain incline this year.
• Stay on small terrain features.
• Stay on simpler terrain (http://www.avalanche.ca/cac/library/glossary/a-z?index=A - ATES).
• Avoid avalanche start zones and tracks if possible.
Human Factors
In my experience, a significant proportion of serious accidents involving PWLs occur in late winter and spring on blue-sky days. I suspect there are a number of factors at play:
• It takes at least several days for PWLs to adjust to stress from new snow or wind events. People don’t wait long enough after a storm before they push out on a nice day.
• It takes at least a couple of days for most non-persistent, storm snow instabilities (which might trigger a step-down avalanche) to settle out. People don’t wait long enough after a storm before they push out on a nice day.
• On clear days, warming air temperatures and strong solar radiation can quickly destabilize slopes or cornices above, which then trigger a PWL or a step-down avalanche. People don’t look up enough, and they tend to underestimate the strength of the sun when assessing warming and solar radiation on slopes or cornices far above, especially if they are in the shade in the valley below or on a “cold” slope such as a north or east aspect.
• There’s less tendency to stop and reassess current, local conditions in good weather. People miss changes happening around or above them.
• People are more willing to push into bigger, steeper, more complex terrain when the weather is good.
• People ride more aggressively on blue-bird days.
• People tend to discount their intuition or “gut feel” more on blue bird days. If something doesn’t feel right, they are more willing to push on a clear warm day than on a cold, foggy, snowy day.
In addition, there’s some kind of dynamic that encourages people to make poor decisions when they are in large groups. Perhaps:
• There’s a false sense of security that comes with being in a group that’s all doing the same thing in the same place at the same time.
• Less experienced people in the group assume that there is someone more experienced who knows what they are doing and will ensure things are safe.
• People are unwilling to speak about their concerns or worries in front of other people.
If any of the above factors is at play, and especially if more than one are a potential, you should very carefully examine your motivation for exposing yourself to slopes where PWLs are known or suspected to exist. It is strongly recommended you back off and go to slopes where PWLs are not an issue. Or choose low angle, simple terrain that is not exposed to slopes above.
Read the full article at: http://www.avalanche.ca/cac/library/researchandarticles/PWLpaper0910
Please repost or distribute this information freely.
Karl Klassen
kklassen@avalanche.ca
On behalf of the CAC and all its staff as well as from my family and I, I extend sincere condolences and sympathies to the families and friends of victims of the recent fatal avalanches. In addition we send our hopes for a speedy and full recovery to those who were injured.
Following is an excerpt from a paper posted on the CAC website that discusses the current avalanche problems in many areas of the BC interior mountains. The advice contained here is applicable to most areas of the Columbia Mountains and North Rocky Mountains from MacKenzie in the North to the US border in the south and between Prince George, Williams Lake, Kamloops, Kelowna and Osoyoos on the west and Chetwynd/Tumbler Rige, Valemount, Golden, and Cranbrook on the east. In addition, last I heard, the South Chilcotin Mountains north of Pemberton also have a persistent weak layer (PWL) problem.
Before I go on, I must stress there is no 100% guarantee of safety in the mountains. You could be caught in an avalanche, injured, or killed even if you follow every piece of advice in this discussion and “do everything right.” That said, avalanche accidents are preventable—it’s up to you to get the training, information, and appropriate equipment to properly manage your risk if you choose to go into the mountains.
My intention is not to scare people out of going into the mountains. It is possible to manage risk, maintain reasonable margins of safety, and make informed decisions in the conditions we are currently experiencing. But my personal approach to a snowpack like this one is very different than when there are fewer or no PWLs involved. Local knowledge of the snowpack and experience with similar conditions are critical components in managing risk this winter. A high level of training and experience are required to tackle large pieces of terrain in a PWL winter.
Persistent weak layers like those currently in the snowpack are among the most difficult of all avalanche problems to assess, predict, and manage. Even with extensive training and over 30 years professional experience, I struggle with the current combination of “low probability-low frequency-high consequence.” That is, it’s often difficult to trigger a deeply buried instability and the number of avalanches you see is low, but the consequences if caught in a deep slab avalanche are very serious due to the size and mass of the slide. The answer lies in making decisions based on what you know about a slope, its history of avalanche activity over the season, slope use patterns (e.g. compaction), and/or stabilization (avalanche control) measures. In the absence of such knowledge or without the training to properly assess the information that is available to you, the only reasonable way to manage your risk is by leaving a wide safety margin wherever a PWL is known or suspected.
Terrain Choices and Travel Techniques
PWLs are associated with high uncertainty and low confidence. With PWLs I don’t ask: “Will it slide?” I do ask: “When it slides, what will happen to me or my partners?” This approach leads to greater margins for error, which in my opinion, is the best way to manage risk at times and places where confidence is low. With PWLs, I am extremely careful in choosing what terrain I use, when I go there, and how I manage my groups. Here are some general tips for managing risk at any time and some specific ideas for dealing with PWLs in general and the specific PWL problems we face this season:
• DO NOT stop, regroup, or park in avalanche paths.
• DO stop, regroup, or park only in safe areas where avalanches will not start or run through/over:
o High points.
o Ridges above start zones.
o Dense timber well away from the track or runout zone.
• Eliminate or minimize exposure to terrain traps, such as:
o Depressions
o Gullies
o Creek beds
o Sudden transitions from steep to flat (lakeshores, benches, road cuts, etc.).
o Slopes where an avalanche might carry you:
Over a cliff.
Into trees.
Against obstructions such as rocks or boulders.
• Take a more conservative overall approach in areas where this year’s PWLs are more prevalent. Find out where they are a problem and current conditions by checking the information at: Bulletins : Bulletins : Canadian Avalanche Centre : avalanche.ca.
• If you must travel in or through start zones or tracks, go one at a time from safe spot to safe spot.
• Go one at a time or spread out when travelling in or through avalanche runout zones.
• Take a more conservative approach at Treeline and Alpine elevations in the current conditions.
• Take a more conservative approach on shaded aspects in this year’s condition. If you are riding good powder, you are in the bulls eye for triggering a PWL avalanche.
• Avoid slopes that have rocks and scattered trees sticking out of the snow.
• Avoid unsupported terrain features (that is pronounced convexities or rolls).
• Stay on low angle slopes that are less than 30o incline. While this is a general rule and is often quoted, it may be of limited use this year as we are seeing avalanches running on slopes as low as 20 degrees. I suggest an very conservative approach to terrain incline this year.
• Stay on small terrain features.
• Stay on simpler terrain (http://www.avalanche.ca/cac/library/glossary/a-z?index=A - ATES).
• Avoid avalanche start zones and tracks if possible.
Human Factors
In my experience, a significant proportion of serious accidents involving PWLs occur in late winter and spring on blue-sky days. I suspect there are a number of factors at play:
• It takes at least several days for PWLs to adjust to stress from new snow or wind events. People don’t wait long enough after a storm before they push out on a nice day.
• It takes at least a couple of days for most non-persistent, storm snow instabilities (which might trigger a step-down avalanche) to settle out. People don’t wait long enough after a storm before they push out on a nice day.
• On clear days, warming air temperatures and strong solar radiation can quickly destabilize slopes or cornices above, which then trigger a PWL or a step-down avalanche. People don’t look up enough, and they tend to underestimate the strength of the sun when assessing warming and solar radiation on slopes or cornices far above, especially if they are in the shade in the valley below or on a “cold” slope such as a north or east aspect.
• There’s less tendency to stop and reassess current, local conditions in good weather. People miss changes happening around or above them.
• People are more willing to push into bigger, steeper, more complex terrain when the weather is good.
• People ride more aggressively on blue-bird days.
• People tend to discount their intuition or “gut feel” more on blue bird days. If something doesn’t feel right, they are more willing to push on a clear warm day than on a cold, foggy, snowy day.
In addition, there’s some kind of dynamic that encourages people to make poor decisions when they are in large groups. Perhaps:
• There’s a false sense of security that comes with being in a group that’s all doing the same thing in the same place at the same time.
• Less experienced people in the group assume that there is someone more experienced who knows what they are doing and will ensure things are safe.
• People are unwilling to speak about their concerns or worries in front of other people.
If any of the above factors is at play, and especially if more than one are a potential, you should very carefully examine your motivation for exposing yourself to slopes where PWLs are known or suspected to exist. It is strongly recommended you back off and go to slopes where PWLs are not an issue. Or choose low angle, simple terrain that is not exposed to slopes above.
Read the full article at: http://www.avalanche.ca/cac/library/researchandarticles/PWLpaper0910
Please repost or distribute this information freely.
Karl Klassen
kklassen@avalanche.ca
