While up to thousands of people read the daily backcountry avalanche advisory, there is a distinct difference between simply reading the danger rating of the advisory and heeding the travel advice for the specific avalanche problems described in the advisory. Not all avalanche problems can be managed appropriately with the same travel strategies.
Tahoe National Forest avalanche forecasters produce daily avalanche advisories for the Sierra Avalanche Center public/private partnership program. These advisories provide an overall danger rating for the region using the North American Avalanche Danger Scale and, more importantly, provide information on the current regional avalanche problems based on the nine different types of classified avalanche problems that may be encountered in a backcountry setting.
The unsophisticated backcountry traveler tends to fixate on the overall danger rating. That overall rating, more than anything else, becomes the driver of decision making. This is a misguided approach to decision making in avalanche terrain. It does not give consideration to how specific avalanche problems differ in relation to appropriate travel techniques for avalanche avoidance.
The more savvy backcountry traveler is focused much more on these specific avalanche problems rather than on the overall danger rating. This traveler will have made the day’s travel plan based on the different travel advice for the specific avalanche problem(s).
For example, two different avalanche problems that warrant distinct travel techniques are wind slabs and persistent slabs. These problems could exist on days with the same danger rating, but necessitate different approaches to maintain safety. Wind slabs that have formed as snow drifts onto leeward slopes are often easily identified below cornice features and/or appear as pillows of deeper new snow. These wind slabs tend to be confined to specific terrain features and have visually distinct boundaries, making them easy to avoid with appropriate decision making. In many cases, nearby small low-consequence test slopes of a similar aspect and slope angle to the potentially dangerous terrain can be safely tested with ski or snowmobile cuts.
Persistent slabs, on the other hand, are a much more challenging avalanche problem to manage. Persistent weak layers form most commonly in this region at the base of the snowpack early in the season, and near a crust within the snowpack at any point during the season. Travel advice associated with persistent slabs encourages greater caution than is often required when managing wind slabs. Persistent slabs often have boundaries that are not visually defined and can be triggered remotely, which is when an avalanche releases some distance away from the trigger point. Ski or snowmobile cuts cannot be performed safely as with wind slabs, as slope failure often occurs once a person is well out onto the slab. Thus, persistent slabs require a different set of travel plans and decision-making skills, although the overall danger rating may have been the same.
The savvy backcountry traveler will take this increased potential for remote triggering and lack of easy visual identification into account when route planning and moving around a specific slope or drainage. Planning for where an avalanche is likely to occur and what areas it is likely to overrun in the lower terrain are critical. For example, I may have decided not to descend a 30-degree angle slope during persistent slab conditions. This was not because I was concerned about an avalanche on that 30-degree slope, but because of the potential for an avalanche to funnel from a steeper adjacent slope into the bottom of the 30 degree slope, should I cause a remote trigger.
Trying to make these types of decisions based on the overall danger rating alone would make it impossible to do much more than get lucky. Successfully ascending or descending a slope without triggering an avalanche does not necessarily mean that a good decision has been made. If the decision-making process was data sparse, driven by excitement, or fueled by heuristics — essentially, a loosely educated guess — in reality, it was a lucky day. Unfortunately, the feedback is that since no avalanche occurred, the decision must have been a good one.
Heed the advisory, don’t just read the advisory. Get training on how to make data-based decisions in the backcountry rather than just getting by on luck. It may take a few years, or a decade or two, but eventually that luck will run out.
~ Brandon Schwartz is the lead avalanche forecaster for the Tahoe National Forest/Sierra Avalanche Center. For more information, visit sierraavalanchecenter.org.
