Rob Coppolillo

A shortened version of this article, along with photos from Matt Kennedy, appeared in The Avalanche Review in Fall 2024.

Rob Coppolillo, February 9, 1970 — April 18, 2024

On April 18 we lost one of our great mountain souls. Rob Coppolillo died from a crevasse fall while ski guiding on the Icefall Traverse near Golden, British Columbia. He leaves behind his wife Rebecca Yarmouth and twin 14-year old sons Dominic and Luca. 

Rob was a devoted father, husband, guide, writer, chef, story teller, and a friend to all. He grew up in Denver, went to college in Boulder where he lived in the road cycling scene, wrote about road cycling, and hosted legendary parties. Later in Boulder he shifted to climbing, skiing, and guiding. In 2015 he received his IFMGA Mountain Guide license, the Ph.D of mountains. With his family, he lived in Chamonix, France, then settled in Seattle where he continued to guide, teach avalanche courses, and write.

Rob was in his own category. He was a loyal friend with everyone, 300 of which were his best friend. “Preferring the hug to the handshake,” said Timmy O’Neil. Rob would give you all of himself, being fully present, fully engaged, bringing out the best in everyone. His constant dinner parties were full of Italian food, wine, friends, and laughter.

Rob was also known to be profanely funny, putting everyone in stitches, at humor that would have anyone else cancelled. “In one breath he could tell the dirtiest joke. In the next he could give you a lesson in Italian wines,” said Jimmy Mohan. “He’s Hunter S. Thompson meets Bill Murray,” said Bob Soderstrom. Extremely well-read, and he’s under the impression life is a performance piece. “It was this line between unbelievably endearing and totally inappropriate at all times,” said Rebecca.

“We, and the world, need more Rob,” said Timmy O’Neil

Rob thought outside the box in which most mountain guides could be placed. A voracious reader, with a diverse intelligence, and a mind further liberated by MDMA, he was open to ideas, absorbed them, and put them to use. He bucked the corporate America guide service norm in favor of working for himself and making a living wage when guiding and teaching avalanche courses. He was fascinated by the human mind and how we think in the avalanche patch. Writing took his curiosity and knowledge to the next level. 

In addition to many magazine and online article, Rob wrote three books. During his cycling years he wrote, Holy Spokes!: A Biking Bible for Everyone. When he shifted to guiding, he wrote The Mountain Guide Manual with Marc Chauvin and The Ski Guide Manual. Rob’s last article for The Avalanche Review—The Wolverine and the Mercenary (TAR 42.2)—shares how we tell ourselves stories, some of them detrimental when in the avalanche patch, and how we can turn those stories into safety. The article shows Rob as the perpetual thinker, “I started tinkering with this idea a couple years ago.” Then, later in the article, “Beware the skier/patroller/guide with only answers, never questions.” Rob shared plans for his next book that would go beyond guiding and help workers in other risky professions make better decisions and reduce risk. 

Perhaps his favorite method for exploring ideas was to debrief. “As soon as where we were out of the mountains his first question would be, ‘Where were we most at risk?’” Says IFMGA Mountain Guide Mikey Arnold, “It wasn’t about climbing or skiing the hardest. It was about being in the mountains, and then it was more than that, to understand risk, mindset. He had no hesitation with talking about what happened, whereas others would hole up.” 

If Rob’s accident had happened to anyone else, Rob would have circled up with guides and beers to learn, to avoid making that mistake himself, and help others avoid that mistake. Rob was a seasoned master at finding the learning points, without second guessing someones’ decisions. Rob may have reminded us to wear a tether from our belay loop to our shoulder strap when glacier skiing. He’d remind us to aim for skiing on glaciers with a thick seasonal snowpack that bridge the cracks. Rob would tell us the probe is our best friend on glaciers: probe for snow thickness, bridge thickness, and rest areas. He’d tell us to be diligent about group gear checks before heading out for the day. Most find this much diligence exhausting, turning a backcountry vacation into mental PowerPoint of checklists and acronyms, but Rob showed us how to make safety fun.

“Rob’s death was tragically unlucky,” said King Grant, who was with him at Icefall. Rob was a master at reducing risk. He was smart, cautious, and thoughtful in the mountains. He wasn’t pushing it. He didn’t deserve it. It was horribly unfair. All he did was take a step in wrong direction to take a leak. Just as us mountain guides have done thousands of times before. But we’ve been lucky. The mountains are dangerous and painfully unfair. We (I) need to be more diligent in the uncaring mountains. To be a safer and better person, like Rob showed us. 

We miss you so much brother. 

Urnal Facets: A Fourth Type of Near-Surface Faceting

This article originally appeared in The Powder Cloud, March 25, 2024. Minor revisions here.

Hey, Northerners! Have you ever skied soft snow, weeks after the last storm, that has been preserved by the mid-winter bitter cold? Some call it recycled powder or settled powder, but it’s actually an undocumented type of snow. Colloquially known as urnal near-surface facets. These facets may preserve good skiing while on the surface, but once buried, they often create a persistent weak layer for avalanches.

Urnal faceting is unique to the wintery north, such as central Alaska, where the sun doesn’t shine or its oomph has been filtered out by its low angle. This consistent cold, combined with clear skies, causes the snowpack’s top layer—30 cm—to maintain a steep temperature gradient that’s conducive to faceting.

Near-surface faceting produces a layer of small (up to 1 mm) faceted crystals on the top of the snowpack. In 1998, snow scientist Karl Birkeland presented three processes that form near-surface facets, depending on the source of the steep temperature gradient. 1) Diurnal near-surface faceting occurs from a daily cycle of warm days and cold, clear nights. 2) Radiation near-surface faceting occurs from a balance between incoming solar radiation and outgoing longwave radiation. 3) Melt-layer near-surface faceting occurs when new cold snow is deposited on a melted-layer and is followed by clear skies.

The different near-surface faceting processes are driven by changing the energy balance inputs; temperature, sun, or a melt-layer. It’s a continuum of processes. Birkeland also mentions a fourth category that occurs at high latitude, which is what we’re calling urnal facets, a term possibly coined by Alaska helicopter ski guide Henry Munter. It’s like diurnal faceting, but without the daily cycle. While urnal faceting is a specific term, it’s okay to simply call these near-surface facets, or surface facets. They often form together with surface hoar—the frozen equivalent of dew that forms a weak and persistent layer—producing a double whammy weak layer once buried.

The snowpack temperature profile during urnal faceting remains consistent during the cold and clear weather. It keeps a steep temperature gradient in the top 20-30 cm of the snowpack. At about 30 cm depth is a distinct kink in the temperature profile where it shifts to a shallow temperature gradient to the ground.

So, the big question is, why is the temperature profile kinked? It other words, why doesn’t the temperature profile become a straight line as a shallow temperature gradient throughout? I took this question to the world authority of near-surface faceting, Karl Birkeland.

Birkeland says that a number of influences keep the temperature profile kinked: 1) snow is a very effective emitter of longwave radiation, 2) space is really cold, and 3) when the sky is clear so much longwave is emitted that the snow surface just cools and cools. “Our sense is that the end result is that the rest of the snowpack is just unable to keep up with that heat loss, especially since conduction within the snowpack is not as efficient for energy transfer as longwave losses from the surface.”

The original diurnal faceting diagram from Birkeland’s 1998 paper. Urnal faceting is effectively the night portion (right side) of his diagram in which the snow surface is losing longwave radiation both night and day, while the temperature around 30 cm depth remains relatively warm.

January 2022 at Turnagain Pass was a good example of an urnal faceting and avalanche cycle. From January 1-7 the skies were clear, the air temperature was around 0°F, and the wind was light (Schauer and others 2023). A storm on January 8-13 brought snow, wind, and avalanches releasing on the buried layer of urnal facets. 

This chart shows the snow temperature at the Tincan study site at Turnagain Pass, Alaska during the January urnal faceting cycle. The vertical temperature profile (red line) shows a distinct turn in the temperature profile at 300 cm which is the snow surface. From about 300 cm to 270 cm the temperature gradient is steep—over 10°C per 10 cm—and well beyond the 1°C per 10 cm required for faceting metamorphism. At 270 cm the temperature profile kinks between the steep temperature gradient above and the shallow temperature gradient below. 

Small faceted crystals about 0.5 mm across formed by urnal near-surface faceting at Turnagain Pass, Alaska. 

For recreational skiers, it’s good to keep urnal faceting in perspective. It is yet another fascinating attribute of the snowpack. Having a keen interest in snowpack, and nature in general, is a good thing. But understanding the nuances of urnal faceting doesn’t necessarily improve your backcountry safety. What’s important here is that facets form a persistent weak layer once buried. Persistent weak layers are unpredictable and kill the most skiers. It doesn’t matter how they’re formed.

References

• Birkeland, Karl. 1998. Terminology and Predominant Processes Associated with the Formation of Weak Layers of Near-Surface Faceted Crystals in the Mountain Snowpack. Arctic and Alpine Research 30(2):193. 

• Schauer, Johnston-Bloom, McKee and Kennedy. 2023. Crusts and Facets: A Case Study of a Season with Deep Issues Near Girdwood, AK. Proceedings of the International Snow Science Workshop.

Avalanche Uncertainty Scale

The Avalanche Review printed this article in spring 2024. Minor revisions here.

Confidence? Are you kidding? Hell yeah I’m confident! I understand the snow and I can ski that slope. If it avalanches, I’ll ski out. What’s the problem?

Backcountry skiers have confidence. Lots of it. How else can we venture into big dangerous mountains where avalanches pummel down? This (over)confidence has been engrained in our psyche over millions of years for survival. The problem is, it doesn’t always help us avoid avalanches when backcountry skiing. To better avoid avalanches, it helps to shift our thinking to the antonym of confidence: uncertainty. By acknowledging that we don’t fully understand the avalanche problems, we can identify gaps in our knowledge, work toward reducing those gaps, and add margins for safety. For this article, uncertainty is defined as the lack of information, knowledge or understanding about avalanche problems. 

“One thing we know about risk management is that it tends to get worse when our uncertainty increases.”

— Ian McCammon

Currently, a scale of avalanche problem uncertainty doesn’t exist. A simple uncertainty scale would allow us to better incorporate uncertainty into our thinking and discussion, both at the recreational and professional level. This article describes the sources of uncertainty, proposes an avalanche uncertainty scale, and how to use it. 

CAA InfoEx Confidence Scale

The closest thing to an uncertainty scale are the Confidence Ratings (below) for the Hazard Assessment charts from the Canadian Avalanche Association InfoEx. Their definition of confidence is “an expression of the degree of certainty about a prediction of expected conditions in the future.” One option for an uncertainty scale is to invert the Confidence Ratings, so high confidence would become low uncertainty, and low confidence would become high uncertainty. This would be a good start, but more specifics would help.

High Confidence

The forecast is based on high-quality information and the nature of the issue makes it possible to render a solid judgement. A 'high confidence' rating does not imply fact or complete certainty however, and such judgements still carry the risk of being wrong.

Moderate Confidence

The information used to produce the forecast is credibly sourced and plausible, but it is not of adequate quality or sufficiently corroborated to warrant a higher level of confidence.

Low Confidence

The credibility or plausibility of the information used to produce the forecast is questionable, or the information is too fragmented or poorly corroborated to make solid judgements, or there are significant concerns regarding problems with the sources.

Sources of Uncertainty

Uncertainty can be from natural sources or knowledge sources (CAA 2016, Jamieson and others 2015). Natural sources (aleatory) of uncertainty include weather and snowpack variability over terrain. Knowledge sources (epistemic) of uncertainty come from limited field data or limited understanding about the topic. To best suit both recreational and professional users, a subset of sources are used in this scale. These sources include: 

1. Accuracy of field data.

Collecting different data reduces uncertainty, while more of the same data does not reduce uncertainty. Credibly-sourced field data will also reduce uncertainty better than poor field data. For example, the quality of data at Teton Pass can be as high as from the Alaska Range, but the accuracy at Teton Pass will be better because of the larger sample size. 

2. Problem uncertainty.

Each of the nine avalanche problems—or five in the European Avalanche Warning System model (EAWS 2017)—have different inherent levels of uncertainty. For example, dry loose problems have low uncertainty (higher predictive snow behavior), while deep slab problems have high uncertainty (low predictive snow behavior) (Wagner and Hardesty 2014). Uncertainty can also arise from any attribute of the current problem including type, location, likelihood (sensitivity and distribution), size, and danger (Statham and others, 2017). For example, weak layer distribution can have low uncertainty, as when a uniform layer drapes the terrain. Or distribution can have high uncertainty, as when a surface hoar layer was partially blown down before burial. 

Another way of looking at problem uncertainty is through the summary statement of avalanche danger. The middle of the danger scale, at moderate and considerable, tends to have higher uncertainty…it might avalanche. Contrast that with low danger, where uncertainty is usually low and it probably won’t avalanche. Uncertainty is also low at high or extreme danger where avalanches are likely or even certain…it probably will avalanche.

3. Effect of the next weather system.

Weather forecast further into the future, or for larger areas has greater uncertainty. For example, weather forecasters and/or models may be unsure if the approaching system will result in 0.5 or 2 inches of snow water equivalent, or how the next storm layer will bond to the old snow surface. Climate change adds further uncertainty to avalanche forecasts as historical records may not indicate current trends.

4. Skier knowledge, experience, and understanding.

A backcountry skier’s level of uncertainty about an avalanche problem may vary based on their level of knowledge, experience, and their understanding of avalanches. For example, a new backcountry skier may not be able to recognize an avalanche problem, while a more experienced skier could recognize an avalanche problem, but dismiss the uncertainty due to a high risk tolerance.

Avalanche Problem Uncertainty Scale

This scale is for the uncertainty of avalanches, including type, location, likelihood or size. Since avalanche uncertainty can not be calculated (Atkins 2023), users must use their own judgment to determine if a rating is appropriate for a scenario. The sources of uncertainty can be one or more of the sources listed above, in addition to the complexity of the interaction of the factors involved. This uncertainty is not the uncertainty, but it is your uncertainty, or the team’s uncertainty. 

This uncertainty scale can be used while trip planning, on guide meeting forms, in avalanche courses, and in avalanche-avoidance language. It is a sense-making aid to help skiers choose appropriate terrain and routes for the the conditions and team. It became an important addition to guide meetings and avalanche courses at our Alaska Guide Collective. Uncertainty discussions usually involve a reason for the uncertainty rating. For example, “I’d say we have high uncertainty above treeline because we haven’t been there in a week.” While this scale could be more specific, with checkboxes for each category, I have kept it simple for ease of use. This scale is not a refined or accepted scale, but rather the starting point to further discussion.

Low Uncertainty

The accuracy of field data is sufficient for confident decisions; the avalanche problem(s) have a predictable behavior; the effect of the forecast weather on avalanche conditions is well understood; or the team has sufficient knowledge and experience with the problem. Travel advice: Low uncertainty does not imply certainty and this judgment still carries the risk of being wrong. Apply normal caution and margins for safety. 

Moderate Uncertainty

The accuracy of field data is limited or of moderate quality; the avalanche problem(s) have a varied behavior; the effect of the forecast weather on avalanche conditions is uncertain; or the team has some knowledge and experience with the problem. Travel advice: Collect different field data which may reduce uncertainty. Use extra caution and wide margins for safety. 

High Uncertainty

The accuracy of field data is limited or of poor quality; the avalanche problem(s) have an unpredictable behavior; the effect of the forecast weather on avalanche conditions is poorly understood; or the team has little knowledge and experience with the problem. Travel advice: Plan route options that account for the low confidence. Maintain wide margins for safety including turning around. Collect different field data which may reduce uncertainty. 

References

• Canadian Avalanche Association InfoEx. 

• Bruce Jamieson, Pascal Haegeli and Grant Statham. Uncertainty in Snow Avalanche Risk Assessments, GeoQuebec. 2015.

• Dale Atkins. Uncertainty Versus Risk, The Avalanche Review 42(1) p28-32. 2023.

• European Avalanche Warning System, Typical avalanche problems, approved by General Assembly of EAWS. 2017. 

• Statham and others. A Conceptual Model of Avalanche Hazard. Natural Hazards. 2017.

• Wendy Wagner and Drew Hardesty. Travel Advice for Avalanche Problems, Proceedings of the ISSW. 2014.

• Technical Aspects of Snow and Avalanche Risk Management: Resources and Guidelines for Avalanche Practitioners in Canada. Canadian Avalanche Association. 2016. 

Thank You for Helping With this Article

Aaron Diamond, Andrew Schauer, Bruce Tremper, Dale Atkins, Elliot Gaddy, Henry Munter, and Nick D’Alessio. 

Luck and Avoiding Avalanches

The Avalanche Review printed this article in spring 2024. Minor revisions here.

The next skier triggers the entire face. Conditions and partners align to make skiing in extreme terrain feel easy. The local avalanche guru dies in an avalanche. As Gallatin Avalanche Center director Doug Chabot says, “Luck is real, both good luck and bad luck.”

Luck can be defined as a chance occurrence that affects us. Luck is out of our control and unpredictable. What we can do is improve skill, which minimizes luck. Understanding this need to improve skill and reduce luck is important because avoiding avalanches does involve luck.

How Much Luck is Involved with Avoiding Avalanches?

In Michael Mauboussin’s book The Success Equation (Mauboussin 2012), he writes, “When a measure of luck is involved, a good process will have a good outcome but only over time.” Cause and effect are loosely linked in the short run. By that description, avoiding avalanches includes luck. Over a few tours or a season, an amateur may trigger as many unintentional avalanches as a professional, but over the long haul a professional will trigger less unintentional avalanches for the number of days out.

Mauboussin also describes how to test whether an activity includes luck. “Ask whether you can lose on purpose. In games of skill it’s clear you can lose intentionally, but when playing roulette or the lottery you can’t lose on purpose.” By that test, avoiding avalanches includes some luck because you can’t always lose (get avalanched) on purpose. 

“The lion tamer has the book on lion taming. She goes into the cage and she does everything by the book, but she still gets eaten by the lion.”

— Drew Hardesty, UAC 2023

Using myself as an example, I have spent decades working at improving my avalanche-avoidance skills, but luck is still involved. Although I have never been avalanched, I have unintentionally started many avalanches, a client of mine was avalanched and not hurt, and my climbing partner was killed by an avalanche. All of these can be viewed as combinations of good skill, poor skill, good luck, and bad luck. 

The Stories We Tell Ourselves 

Our experiences with avalanches can be difficult to understand and seem random. For example, an avalanche accident involving friends, or deep slab avalanches can appear as random outliers. The human mind creates cause and effect stories to simplify and better understand these complex experiences, just like everything we don’t truly understand. This pattern seeking is called the narrative fallacy. I didn’t trigger the deep slab because…. 

In addition to not understanding seemingly random events, the human mind also does poorly at understanding probabilities. The gambler’s fallacy is another narrative we tell ourselves in which we equate a random string of good luck to skill. Say we nail five days of skiing with stable snow, stable weather, and stable partners. Was that skill like we tend to think, or did we get lucky? 

An important way of thinking about probabilities is that above average outcomes tend to be followed by events that are more average. “Any activity that combines skill and luck will eventually revert to the mean,” says Maubuossin. For example, you may have good luck and ski many days in avalanche terrain during considerable avalanche danger. Reversion to the mean explains that your good luck will probably run out since the average likelihood for considerable danger is “human-triggered avalanches likely.”

“Skill and experience are how you change probabilities. Luck determines what side of the probability you fall on. ”

— Aaron Money, avid backcountry skier

Luck-Skill-Continuum

Gaining knowledge and experience don’t improve our luck. They improve our skill. Our ability to avoid avalanches lies on a luck-skill continuum. At one end of the spectrum are avalanche amateurs who rely more on luck. At the other end are professionals who rely more on skill, although they take on more lifetime risk. The important thing to consider is where your actions lie on this luck-skill spectrum. Then you can shift your actions and training to reduce luck, and move toward skill. It’s still a combination, though. One can be skilled and get lucky, or skilled and unlucky. 

Despite its sordid origins, The Rumsfeld Matrix helps explain how luck plays into avoiding avalanches. Former Secretary of Defense Donald Rumsfeld said there are four quadrants of risk (Krogerus and Tschäppeler 2018). Luck would fall into the quadrant of unknown unknowns, the stuff we don’t know that we don’t know.

The Rumsfeld Matrix for backcountry skiers helps explain where luck lies within our decisions.

The Rumsfeld Matrix can be viewed on a bar graph with ranges for amateurs and professionals in avalanche terrain. The amateur relies more on luck. The professional relies more on knowledge, experience, and intuition. Neuroscience professor and backcountry skier Russ Costa says, “I think about it as uncertainty reduction, and the uncertainty that remains (there's always some) is luck.”

Amateurs rely more on luck than professionals. Professionals rely more on knowledge, experience, and intuition.

Bayesian updating is a useful way to describe a shift from luck to skill. Say the avalanche forecast danger is moderate for a storm slab problem, so you plan to ski in challenging terrain. Once in the field you notice numerous recent avalanches. Rather than staying on challenging terrain and relying on luck, or giving up and going home, you update your prior knowledge with this new information and change the slope-scale danger from moderate to considerable, and shift from challenging to simple terrain.

Improve Your Skill, Reduce Your Luck

When people say, “It all comes down to luck,” it prevents them from learning. As National Avalanche Center specialist Chris Lundy says (UAC 2023), “Luck in the backcountry is what makes it hard to develop expertise.” The wicked learning environment is due to the effect of luck on avalanche decisions. Luck in the complex avalanche environment creates unjustified confidence in those who are less skilled and experiencing good luck, and unjustified doubt in those who are skilled and experiencing bad luck. This makes avalanche expertise only attainable through a combination of experience and deliberate practice to learn the right lessons. Experience alone doesn’t develop avalanche expertise. Chabot says, “What we can control is being trained, fit and skilled so we can minimize the bad luck (he's buried and I have to dig him out fast), and maximize good luck (the slopes are more stable than I thought).”

Focus on the Process, Not the Outcome

With help from the Narrative Fallacy, we often confuse skill and luck. Our initial reaction to hearing about an accident is, I wouldn’t have done that, and use the explanation of Their poor skill, as a way to simplify and understand those mistakes. This self-serving bias also leads us to believe that I made all the right decisions, but then got unlucky. These ways of thinking about luck and skill fit into a process-outcome matrix (Parrish 2023).

Our confusion with skill and luck can be seen in a Process-Outcome Matrix (Parrish 2023). 

“Amateurs focus on the outcome. Professionals focus on the process.”

— Shane Parrish, Farnam Street

In environments that involve luck, a good outcome (eg. not getting avalanched) does not mean the process (eg. making observations) was good. “In activities where luck plays a strong role, the focus must be on process….where luck is a strong force, the link between process and outcome is broken.” says Mauboussin. In Clear Thinking (Parrish 2023) Shane Parrish calls it “The Process Principle: When you evaluate a decision, focus on the process you used to make the decision and not the outcome.” Improve process by gaining knowledge, experience, practice, and debriefing to learn the right lessons. Below are some ways to focus on the process to improve your skill and reduce your luck. 

How to Improve Your Skill and Reduce your Luck

1. Debrief. By acknowledging when you were lucky, you can better perceive those situations in the future and adjust course. Debrief at the end of the day to examine your sense- and decision-making process separate from the outcome. Beers and high fives alone don’t count. Asking “Did we get lucky today?” is a good debrief question. 

2. Don’t push your luck. Lucky streaks will end as the outcomes revert to the mean. Say you’ve started ski cutting large avalanches in the backcountry without being caught. Pushing your luck with a wild snowpack will eventually revert to the mean, which means getting avalanched.

3. Be prepared for good luck. If you get the ball, do you know which way to run? Arm yourself with a quiver of trips for when weather, snowpack, and partners align. Get advanced avalanche training and practice those skills so you’re in position when a potentially great new backcountry partner comes along. 

4. Be prepared for bad luck. Consider the consequences of bad luck. If the slope avalanches will I be okay or will I be dead? Make yourself lucky by choosing terrain that has an escape zone and a good runout, so if it avalanches the outcome isn’t “he was unlucky to die,” and is instead “he got lucky to not get buried.” Likewise, train for bad luck by practicing wilderness first aid, avalanche rescue, shelter building, fire building, sled evacuation, etc.

5. Learn from other’s bad luck. Fight your instinctive temptation to think, I wouldn’t have done that. Rather than attributing someone else’s accident to their poor skill, see what you can learn from their experience. Put yourself in their shoes, without the hindsight benefit of knowing about the avalanche. 

References

• Chris Lundy on the Four-Letter Word of Decision Making. Utah Avalanche Center Podcast. January 23, 2023. 

• Mikael Krogerus and Roman Tschäppeler. The Decision Book. 2018.

• Michael Mauboussin. The Success Equation. 2012.

• Shane Parrish. Turning Pro: The Difference Between Amateurs and Professionals. Farnam Street blog, accessed February 25, 2024.

• Shane Parrish. Clear Thinking. 2023.  

• The Avalanche Review. Are We Good or Just Lucky? 36.3. 2018. 

Thank you for helping with this article

Aaron Money, Andrew Schauer, Bruce Tremper, Cathy Flanagan, Chris Lundy, Clint Schmidt, Doug Chabot, Lynne Wolfe, Mark Smiley, and Russ Costa. 

Skiing in Moderate and Considerable Danger

In many regions the avalanche danger hovers at moderate and considerable for most of the winter. This is where the most fatalities occur and where the most uncertainty lies. Plus, anytime we enter a remote region we start with a danger rating of considerable. So where can we ski during moderate and considerable danger and keep risk low?

In a nutshell, I avoid avalanche terrain during considerable danger. In moderate danger, it depends on the avalanche problem. If there is potential for large avalanches that could kill me I avoid avalanche terrain. Here is a more complicated answer:

First, for the simple answer. Use the Trip Planner from Avalanche Canada to relate avalanche danger to an ATES terrain rating. According to the Trip Planner, at moderate danger stay on simple and challenging terrain for normal caution. At considerable danger stay on simple terrain for normal caution. Accidents are infrequent at normal caution, green zone.

The Trip Planner portion of the Avaluator from Avalanche Canada.

Avalanche terrain includes slopes over 30 degrees, or challenging and higher on the Avalanche Terrain Exposure Scale.

Another answer for where to ski in moderate and considerable is to look at the size and distribution of avalanches within the forecast danger rating. Not all moderates are the same, nor are all considerables the same.

Moderate danger is defined as “small avalanches in specific areas; or large avalanches in isolated areas.” Considerable danger is defined as “small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.” It’s wise to avoid avalanche terrain if there is potential for large avalanches. Large avalanches can be deadly even without terrain traps.

The North American Public Avalanche Danger Scale.

An example from the Chugach Avalanche Center forecast for Turnagain Pass for December 30, 2023. The size of these glide avalanches is large to very large. Stay away from avalanche terrain where there is potential for these large avalanches.

The more advanced, and more common, answer is to choose where to ski during moderate and considerable danger based on the current avalanche problems. Each avalanche problem requires a unique way to travel around. For example, moderate danger for a small dry loose avalanche problem may mean it’s okay to ski in avalanche terrain with normal caution. Moderate danger may also be for large and dangerous avalanche problems—deep slab, wet slab or glide—which means stay away from avalanche terrain because they could kill you.

For another example, it may be easy to ski in avalanche terrain with low risk during considerable danger for a wind slab problem if you can see the wind slabs. But blanket those wind slabs with four inches of powder and they become invisible, and then it’s wise to avoid avalanche terrain.

It takes a lot of time in the backcountry and/or advanced avalanche education to effectively use avalanche problems to decide where to ski in moderate and considerable danger.

Dry loose tend to be smaller and more predictable...avalanche terrain can be considered with normal caution. On the other hand, deep slab, wet slab and glide are destructive and unpredictable...avalanche terrain is not recommended.

Chugach Avalanche Center highest danger rating for March for winters 2022/23 on left to 2018/19 on right. There were periods of low danger, but it’s mostly moderate and considerable danger.

In spring and summer the danger goes to low more often. Save your stoke for spring! Unfortunately, the safest option is to avoid avalanche terrain altogether during moderate and considerable danger. If you do go into avalanche terrain, you acknowledge that injury or death is possible.

Guidelines

1. In your early years of avalanche study, use the Avaluator Trip Planner to select an ATES recommendation for where to ski in moderate and considerable danger.

2. Pay attention to the size and distribution of the possible avalanches on the Avalanche Danger Scale that are within the current forecast danger rating.

3. As you gain more knowledge and experience, use avalanche problems to decide when and where to ski in moderate and considerable danger.

4. Avoid avalanche terrain where there is potential for large avalanches.

5. Save your stoke for spring, when danger is more often low.

More Reading

• Avalanche Danger Scale. Utah Avalanche Center.

• Avaluator Trip Planner. Avalanche Canada.

• The Dangerator. Avalanche Canada.

• 10 Things to Consider When the Danger is Considerable. Avalanche Canada.

• Haegeli and others. 2006. The Avaluator, A Canadian Rule-based Decision Support Tool for Amateur Recreationists. Proceedings of the 2006 ISSW.

• Statham and Campbell. The Avalanche Terrain Exposure Scale v2. Proceedings of the 2023 ISSW.

• Wagner and Hardesty. 2014. Travel Advice for Avalanche Problems. Proceedings of the 2014 ISSW.