01What is an Avalanche Bulletin?
An avalanche bulletin (called a forecast in North America) is a daily assessment produced by professional forecasters. It synthesises weather data, snowpack observations and recent avalanche activity to predict conditions for the coming day(s). Modern bulletins go beyond a danger rating — they identify specific avalanche problems, describe where hazards exist (elevation and aspect), and help you make terrain decisions.
02The Danger Scale
The scale rates danger from 1 (Low) to 5 (Extreme in North America; Very High on the European EAWS scale).
- 1 - Low: Natural and human-triggered avalanches unlikely
- 2 - Moderate: Human-triggered avalanches possible on specific features
- 3 - Considerable: Human-triggered avalanches likely; cautious route-finding essential
- 4 - High: Travel in avalanche terrain not recommended
- 5 - Extreme: Avoid all avalanche terrain
In France, ANENA's study of 50 years of avalanche accidents (December 2023) puts 48% of fatal accidents on days when the BERA rated the danger 3 (Considerable). In Switzerland, the SLF also finds that most accidents happen at level 3. People still go out and misjudge the hazard. A low rating does not mean zero risk.
Hazard doubles each step — but deaths peak in the middle
Skier reality: Triggering likely on many steep slopes. Demanding - experts only on steep terrain; reduce slope angle.
Hazard multiples (×1–×16) follow Munter’s rule that the danger roughly doubles per level, and the slope-angle caps follow the Reduction Method (SLF graphical version); both are keyed to the EAWS levels, not published by EAWS. The fatality shares (~80% at Levels 2–3) are approximate, after SLF/EAWS accident statistics (e.g. Techel et al.). Always defer to your local bulletin. Educational only.
Each step up the danger scale is a far bigger jump than the number suggests — Considerable (3) carries several times the hazard of Low, and High (4) climbs steeply again — yet most people die at Considerable, not at High or Extreme, because that is the last rating where serious hazard and open-terrain travel still overlap.
03Avalanche Problems
Bulletins identify specific patterns of instability:
- Storm Slab: new snow bonding poorly; short-lived (hours-days)
- Wind Slab: wind-transported snow on lee slopes; watch for pillows and shooting cracks
- Persistent Slab: slab over a persistent weak layer; can last weeks-months and feel deceptively stable
- Deep Persistent Slab: large avalanches breaking deep; low probability, enormous consequence
- Wet Avalanches: water weakening bonds; travel early on frozen conditions
- Loose Snow: point-release sluffs; dangerous in terrain traps
- Glide Snow (Gleitschnee): the whole snowpack creeps and releases full-depth on smooth ground (grass, rock slabs); look for glide cracks ("fish mouths"), but timing is unpredictable — never travel above, below, or through an open glide crack
- Cornice Fall: overhanging snow collapsing, often triggering the slope below
Reading European bulletins: the labels above are the North American set. Alpine (EAWS) bulletins group instability into five standard problems — new snow, wind slab, persistent weak layers, wet snow, and gliding snow — each with its own icon. They map closely (EAWS new snow ≈ storm slab and loose-dry; persistent weak layers ≈ persistent and deep persistent slab; wet snow ≈ wet avalanches and loose-wet); only the labels differ.
Compare the five avalanche problems
What this means for travel
Trigger sensitivity: The defining trait of this problem — let it drive route choice and timing. How easily your weight sets it off. High means it goes with little provocation — a single skier can do it.
Typical terrain / timing: All aspects, during & after snowfall
Reactive and widespread during the storm window, but consistent and fast-healing — the problem that rewards patience.
How to manage it: Wait 24–48 h after heavy snow; avoid steep, unsupported terrain during loading; re-test bonding to the old surface before committing.
Tap a bar or arrow-key the radar to inspect a trait · arrow-key the tabs to switch problem
Fingerprint scores (0–5) are illustrative teaching values, not measurements. Read your local bulletin for the active problem. Educational only.
04Elevation Bands & Aspects
North American forecasts divide terrain into below treeline, near treeline, and above treeline; European (EAWS) bulletins give elevation thresholds instead (e.g. "above 2,200 m") — danger and problems often vary with elevation, so check every band.
They also specify aspects of concern (compass directions). Aspect matters because of sun exposure (south warms faster → wet problems; north stays cold → persistent problems) and wind loading (lee slopes collect wind-transported snow). Match the aspect rose to your planned route.
The danger rotates around the compass
N: Among the most-loaded orientations — wind slabs and the highest likelihood of triggering concentrate here.
Mid-winter, persistent slab (cold N/E): Faceted persistent weak layers preserved on cold, shaded N/NE/E aspects; sunny S/SW have shed or healed and read lowest. Danger is present all day — this is a terrain-avoidance problem, not a timing one.
Relative danger on a 0–5 scale, N at top.
Illustrative aspect rose — the danger concentrates on specific slope orientations. Always read your local bulletin’s actual aspect/elevation rose. Educational only.
05Likelihood and Size
Likelihood: Unlikely → Possible → Likely → Very Likely → Almost Certain.
Size (destructive potential): D1 (relatively harmless) → D2 (could bury/injure/kill) → D3 (destroy a car or a wood-frame house) → D4 (destroy a railway car or several buildings) → D5 (largest known).
Risk = Likelihood × Size × Consequences. Even an unlikely avalanche can be fatal when the consequences are deadly.
06Applying the Bulletin to Your Plans
- Read the full bulletin — not just the rating. Understand the problems, elevation bands, aspects, and confidence.
- Match it to your route — the elevations, aspects, and slope angles you will travel.
- Make a plan — avoid problematic elevations/aspects, identify safe zones, set decision points, prepare a Plan B/C.
- Observe and reassess in the field — does the snowpack match the bulletin? Any red flags or activity?
Each problem hides on different slopes
This problem is flagged on NE slopes at alpine. Treat this cell as terrain to avoid — favour aspects and elevations the bulletin leaves clear.
Manage it: Wind has loaded the lee NE–E–SE slopes above treeline — find the smooth pillows under cornices and walk around them; the windward ridge two metres away can be bare.
Illustrative terrain signatures (8 aspects × 3 elevation bands). Real avoid-zones come from your local bulletin’s aspect/elevation rose, not this teaching model. Educational only.
07Regional Avalanche Centres
North America: avalanche.org (links to all centres), NWAC (nwac.us), CAIC (avalanche.state.co.us), Utah (utahavalanchecenter.org), Avalanche Canada (avalanche.ca).
Europe: EAWS (avalanches.org), Météo-France, SLF/WhiteRisk (Switzerland), avalanche.report (Tyrol/South Tyrol/Trentino).
08Common Mistakes
- Rating shopping: looking for a low rating to justify your plan
- Ignoring aspects/elevations: focusing only on the number
- Overconfidence at Moderate: most accidents happen at Moderate/Considerable
- Not reading the discussion: missing the reasoning
- Assuming uniformity: local conditions vary from the regional bulletin
- Using yesterday’s bulletin
09Sources & further reading
Sources & further reading. This guide reflects the consensus of the major avalanche-safety organisations and the standard references. Always defer to your local daily avalanche bulletin and hands-on training over any single article:
- **EAWS** — the European danger scale and the five avalanche problems
- **Avalanche.org** — North American forecasts and avalanche-problem definitions
- **SLF** — bulletin science and interpretation
- **ANENA** (France) — avalanche education; the French bulletin (BERA) is issued by Météo-France
- **AINEVA** (Italy) — regional Alpine bulletins
- McClung & Schaerer, “The Avalanche Handbook” — the standard technical reference
Key takeaways
- Bulletins rate danger from 1 (Low) to 5 (Extreme in North America, Very High in Europe); in France, 48% of fatal avalanche accidents happen at Considerable (3), according to ANENA — never treat a low number as zero risk.
- Modern bulletins identify specific avalanche problems (storm/wind/persistent/deep slab, wet, loose, cornice), each needing different management.
- Check every elevation band and the aspects of concern — danger varies by elevation and slope direction.
- Risk = Likelihood × Size × Consequences; even unlikely avalanches can be fatal.
- Read the full bulletin, match it to your route, plan ahead, then observe and reassess in the field.