The avalanche situation today
The avalanche forecast refers to a region of several hundred square-kilometers. For the final decision at a slope this estimate is too rough. That’s why we downscale the regional forecast into a local assessment – with the help of our local observations.
A snow profile is a snapshot from within the snowpack. In situations with persistent weak layers or when signs of instability are absent, a snow pit can provide the clues we’re lacking to assess snow instability, and hence support decision making.
This short video recalls the standard procedures:
To eventually assess snow instability we need to combine the test results with the snowpack layering, i.e. find the weak layer that failed in the profile.
The snowpack layering is unfavorable, if …
Stability test results are unfavorable, if …
The short video explains the standard procedures and the interpretation of the test results.
Single stability test results correctly predict slope stability, so stability at the next larger scale, in only 60 – 80 % of the cases. For a better guess, we need to combine snow profile data with the test results.
Only the process-based thinking may allow for extrapolation. Knowing the origin of the problem, e.g. the weak layer type, we may tell how it formed and where the problem is present in the terrain.
When we talk about snow instability we want to express how likely it is for an avalanche to occur. To be precise, we’d need to say whether we talk about natural release or skier-triggering.
Low stability means that weak layers are likely to fail and cracks will propagate to release the slab that sits on top.
Further reading:
« […] snow instability means […] failure initiation and crack propagation [which] […] control the avalanche release probability. (TAR, 2016)
Simple Observations
Along the trip, so-called simple observations don’t ask for much effort:
Snow pits
If clues for snowpack stability are missing, snow pits can provide such information – but it is harder to come by. The table on right shows the information we can draw from field observations.
Taking decisions in the field isn’t easy. There are a bunch of factors to consider when taking decisions for onesself, and even more though when taking responsability for other folks:
The DCMR framework helps us summarize the avalanche situation and to comapre it with our exerpience to decide.
In a group communication is important to take decisions that everybody is happy with. Here is an example from the field. The DCMR framework helps you communicate your thought about the avalanche situation.
Trip planning starts with selecting a mountain range. Danger level and avalanche problems guide your choice.
To select the suited terrain you want to consider more details from the avalanche forecast: The description of avalanche prone locations and the hazard in the region provide key information at this stage.
The video takes you through these stages.
This video (play from 06:31) shows you how to find the crux slopes along a trip that you plan.
« Evaluation » : For support on local danger assessment and risk management fold out front and back cover on the trip planning notes.
« Observation » : To get the cheat sheet with the observation standards for snow pits fold the front cover in on the snow pit notes.
« Interpretation» : Pull the right conclusions from your observations; fold the back cover in on the snow pit pages.
