| What it is | Layered snow accumulated on the ground |
| Built from | Successive snowfalls & weather |
| Why it matters | Layer structure drives avalanche danger |
| Assessed by | Observation, pits, stability tests |
The snowpack is the total accumulation of snow on the ground, built up in layers from successive snowfalls and weather events. Its internal structure — strong and weak layers and the bonds between them — determines avalanche danger, because a cohesive slab over a buried weak layer is what produces slab avalanches. Understanding the snowpack is central to avalanche forecasting and safe travel.
This is general educational information, not avalanche training.
Layers decide danger
Weak layers like depth hoar within it cause the slab and persistent slab avalanche problems.
Frequently asked questions
What is the snowpack?
The snowpack is the layered mass of snow that has accumulated on the ground over a season. Each snowfall and weather event adds a layer, and those layers change over time, developing into strong or weak layers. The snowpack's structure is what avalanche professionals study to assess instability.
Why does the snowpack structure matter for avalanches?
Because avalanches — particularly deadly slab avalanches — happen when a cohesive slab sits over a buried weak layer that fails. Whether the snowpack contains such weak layers, how well bonded the layers are, and how they're changing all determine the avalanche danger, which is why understanding the snowpack is fundamental to safe winter travel.
How do you assess the snowpack?
Avalanche forecasters and trained travelers dig snow pits to examine the layers, perform stability tests (like compression and extended column tests) to see how weak layers fail, observe red flags (recent avalanches, cracking, collapsing 'whumpfs'), and track weather history. This requires formal avalanche education to interpret correctly.
Sources
- Understanding snowpack — Avalanche.org
- Snowpack structure — American Institute for Avalanche Research and Education