Avalanche forecasts don’t only give a danger level from one to five. They also name the avalanche problem: what kind of avalanche to expect, and why the snow is unstable. US forecasters work with nine of these problem types, Avalanche Canada with eight, and European services with a shorter list built on the same ideas. This video explains all nine through the hidden structure inside the snowpack.
What you’ll learn:
– Loose dry avalanches (sluffs): why they start from a single point and fan out, why they cause fewer than one in ten avalanche deaths according to the Swiss institute SLF, and why terrain traps are the real danger.
– Loose wet avalanches: what pinwheels and rollerballs are telling you, and why the same slope can change between morning and afternoon.
– Storm slabs: how new snow settles into a cohesive slab, how a crack in a weak layer releases the whole plate, and why slab avalanches cause more than 90% of avalanche deaths (SLF).
– The slope angle where most avalanches start: about 30 to 45 degrees.
– Wind slabs: how wind strips one side of a ridge and loads the other, what cross-loading means, and what wind-loaded snow looks and sounds like.
– Persistent slabs: how surface hoar grows on clear, calm nights, the “one degree per ten centimetres” rule for weak faceted snow, remote triggering, and the whumpf.
– The myth that shouting triggers avalanches, and what avalanche centres say actually starts most avalanche accidents.
– Deep persistent slabs: depth hoar, thin spots near rocks, “low probability, high consequence”, and why ski tracks are no proof of safety.
– Powder clouds, which SLF and US forecasters say can reach about 300 km/h.
– Wet slabs: what changes when the snowpack reaches 0 °C, and why their timing is so hard to forecast.
– Glide avalanches: how the whole snowpack slides on grass or smooth rock, and what a glide crack can and can’t tell you.
– Cornice fall: how wind builds overhangs bigger than a bus, and why they can break farther back than people expect.
Chapters:
0:00 Avalanche Problems
0:31 Loose Dry
1:37 Loose Wet
2:36 Storm Slab
3:50 Wind Slab
4:50 Persistent Slab
6:28 Deep Persistent Slab
7:52 Wet Slab
8:47 Glide Avalanche
9:44 Cornice Fall
10:37 Ice Avalanches
10:48 Final Question
Safety note: this video explains mechanisms; it is not avalanche training. Before travelling in avalanche terrain, read your local avalanche forecast, take an avalanche course, and carry and practise with rescue gear. In the US see avalanche.org, in Canada avalanche.ca, in Europe avalanches.org for links to regional services.
Main sources:
– Avalanche.org (US avalanche centres): Avalanche Encyclopedia — avalanche problem types, powder cloud, wet avalanche, surface hoar, depth hoar, human trigger
– Colorado Avalanche Information Center: avalanche problems tutorial
– Avalanche Canada: AvySavvy avalanche problem pages and the Avalanche Canada glossary
– European Avalanche Warning Services (EAWS): avalanche problems and European avalanche danger scale
– WSL Institute for Snow and Avalanche Research SLF: avalanche types; avalanche bulletin “typical avalanche problems”; “Gliding avalanches: the great unknowns”
– Parks Canada: North American Public Avalanche Danger Scale
– US National Weather Service: avalanche safety
– Utah Avalanche Center: FAQ and avalanche myths
– Reuter & Schweizer (2009), “Avalanche triggering by sound: myth and truth”, International Snow Science Workshop proceedings
– Gallatin National Forest Avalanche Center: “The Facet Factory — An Introduction to Snow Metamorphism”
– University of British Columbia (ATSC 113): surface hoar; NSIDC: the science of snow
– SWI swissinfo.ch reporting SLF avalanche statistics, winter 2024–25
Illustrations are AI-generated; narration is synthetic. Diagrams are simplified and not to scale; realistic scenes are illustrations, not photographs of real avalanches or places.
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