Simple Snowpack Assessment Errors That Can Get You In Trouble

01

SEP, 2016

Snow Safety
Backcountry

If you are skiing or riding in the backcountry, then knowing how to assess the snowpack is an essential skill to have in your snow safety arsenal. However, there are some common mistakes that can be easily avoided. Derek Lennon walks us through how we may be getting ourselves into trouble.

article by Derek Lennon

Every skier and rider dreams about making turns through deep powder as it billows overhead — until they trigger an avalanche that is. There is nothing more terrifying than snow shattering like a windowpane beneath your feet. Before you know it you’re hurtling down the mountain at full speed not knowing up from down or left from right — praying that your backcountry partner knows how to save your life. The risk of avalanches is very real and it can happen in a blink of an eye.

Hundreds, if not thousands of people, are caught in avalanches every year. The lucky ones survive to enjoy another day, but avalanche fatalities are always a possibility. The risk of avalanches will always exist in backcountry mountainous terrain where a weak layer, a slab, and a trigger exist. Add in the right slope angle (25°– 45°) and you have the perfect recipe for an avalanche. Ideal ski terrain is often also prime avalanche terrain so safely assessing that risk is the responsibility of every backcountry enthusiast.

 

One Question

Assessing avalanche risk in the backcountry is no easy task. The mountain snowpack is complex with weather, snowfall, aspect, terrain, and the various snow layers underneath your feet all playing their part in its stability. Yet all we want to know is the answer to the ultimate question: Is the slope stable or unstable?

Snowpit - Aspen Backcountry for AIARE Level 1 Certification

Digging a snow pit in the Aspen Backcountry for AIARE Level 1 Certification

Photograph by Matt Doyle via FATMAP

Snow stability is predictable to a certain degree. It’s your job to assess stability every time you venture into the mountains. Pay attention to snowpack, weather, terrain, and human factors. Start with an avalanche course and then slowly grow your experience.

Even with an avalanche certification under your belt, mistakes can be made when it comes to snowpack assessment. To stay safe while skiing or riding in the backcountry, here are some things that you need to do:

“Never assume that your singular snowpack assessment tests are absolute. False stable results are possible for a variety of reasons.”

  • Understand The Seasonal View: Assessing the snowpack begins with the first snowfall of the season. Subsequent storms and weather patterns will dictate future stability. Tune into the snowpack early and regularly to watch it evolve and to monitor stability trends. As the snow starts to fall on the high peaks, watch how this early layer of snow transforms. Will it be a stable base layer or will it be a weak layer to worry about all season long?
  • Read The Avalanche Forecast: Experienced avalanche forecasters write daily avalanche forecasts and weather reports. Read your local avalanche report daily. Check in on new zones you plan to explore long before you go. Avalanche forecasts help to paint a picture of what you might find in the snowpack. Almost every major mountain range has an avalanche centre or government agency where you can check in and get the latest avalanche reports. Find your local avalanche center and bookmark it on your laptop and smartphone.
  • Stability Tests: Master stability tests like the Compression Test, Rutschblock test, Hand Shear, Extended Column Test, and Propagation Saw Test. Learn how to perform these tests and how to read the results. A simple error in performing these tests can give misleading results. You can find more information on how to perform snow stability tests from Gallatin National Forest Avalanche Center, Avalanche.org, American Avalanche Institute (https://vimeo.com/avyinstitute/videos), and K2 Backside Elevated Education. Still, by far the best way to learn these skills is to take an avalanche course from a respected avalanche professional where you can actually get your shovel in the snow.
  • Snowpack Variability: Life would be simple if the snowpack was consistently uniform across the entire mountain range, but it’s not. Snowpack variability can easily throw a curveball into your snowpack assessment. Graupel can form isolated weak layers. Rocks can change the stratigraphy of the snow. Wind can make dense slabs. Aspect can affect layers. Be prepared.
Snowpack error sketch

Look at two very different snow pit profiles sketched above. One represents a shallow, less stable snowpack with multiple weak layers. This snowpit got poor stability test results (ECTPV) The other represents a deeper, more stable snowpack with weaker layers on top of stronger layers. This snowpit appeared stable based on stability tests (ECTX). Always dig into the snow to find out what you are skiing on. It may directly impact what you choose to ski or ride.

Photograph by Derek Lennon via FATMAP

  • Test Pit Location: When assessing the snowpack, dig and perform stability tests in a representative location of where you will be travelling. Find a small and inconsequential test slope to begin your assessment before you venture into bigger terrain. Think about aspect, slope angle, and terrain amongst other factors. Learn more about how and where to dig a snowpit from the National Avalanche Center, Backcountry.com, and Bruce Tremper’s book Staying Alive In Avalanche Terrain.
  • Duplicating Results: It’s easy to dig a pit and get a quick result, but it’s better to dig two or more pits and get multiple results. Never assume that your singular snowpack assessment tests are absolute. False stable results are possible for a variety of reasons.
  • Ignoring Red Flags: When we set our eyes on the prize of traversing vast ranges, climbing distant peaks, or making powder turns through steep couloirs, it’s easy to overlook and ignore obvious snowpack red flags. Look for all of the necessary ingredients for an avalanche. Does harder snow exist over weaker snow in your snow pits? Does the bottom of the snowpack consist of sugary facets? Does the weather promote rapid warming? Did you see any shooting cracks or experience any whoomphs? Is the new snow creating a large load? Did you see signs of recent avalanches? Is wind transporting or blowing snow? It’s amazing what you can see when you remember to look.
  • Terrain Identification: Is the terrain capable of causing an avalanche? If you want to ski it or climb it, the answer is probably yes. Avalanches can occur on any slope with wild snow that has a weak layer, a slab, and a trigger such as a skier. A slope angle of 38° is the prime steepness for avalanches, but in the right conditions, avalanches can occur on any slope between 25° and 45°. Always carry a slope meter or inclinometer with you into the mountains to accurately assess slope angle.
FATMAP Gradient overlays for Vallee Blanche area

Gradient overlay of the cumulation zone atop the Mer de Glacé (Valleé Blanche and variations visible as dotted lines)

Photograph by FATMAP Lennon via FATMAP

  • Human Factors: Humans can easily affect snowpack assessment. Whether we feel like we are under the guidance of an expert or we are overly familiar with the terrain, it’s important to take a step back and not let ego or complacency get in the way of obvious signs of instability.
  • Field Observations: As soon as you enter the mountains, your avalanche and snowpack assessment radar should be turned on. Collect useful data while on the move. Look for signs of stability and instability as you ride the lifts, break the skin track, or set the boot pack. Monitor temperatures, wind direction, signs of avalanches, blowing snow, sky cover, surface forms, precipitation, and other observations — and know what they indicate. Write down what you see so that you don’t forget when you’re the one on the sharp end.
  • Digging: Heli-ski pioneer Mike Wiegele always says, “If you don’t dig, you don’t know.” It takes less than ten minutes to assemble your shovel, dig a snow pit, and assess the snowpack. If you don’t dig down into the snowpack, you will never know what’s under your feet.

Snowpack assessment is serious business. The decisions you make based on what you see in the snow can have a direct impact on your life, as well as others. Keep your skills sharp and fresh. Take an avalanche course. Earn an avalanche certification. Practice with a knowledgeable backcountry partner. Start slow and then gradually ramp up your skiing and riding adventures as you gain confidence in the snow that you’re sliding on. Always play it safe.

If you plan to spend time in the backcountry, seek proper avalanche training. Read the avalanche forecast every day. Gain experience. Go with a partner. Travel wisely.

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