How to read an avalanche bulletin

Why the bulletin matters

The avalanche bulletin is the one daily source on where avalanches are likely, how big, and on which aspects and elevations. The warning services across the Alps publish it every day in winter.

Yet many skiers glance at the danger number, a single digit from 1 to 5, and head out without the details. The number is the bulletin's summary, not the bulletin. The real information lives in the avalanche problems, the danger rose, the elevation bands, and the detailed text that describes exactly which slopes are dangerous and why.

Reading a bulletin properly takes about five minutes. This guide explains every part of the avalanche bulletin, how to interpret it, and how to translate it into concrete route decisions. For the fundamentals of avalanche terrain assessment, see our Avalanche Safety Basics guide.

The European avalanche danger scale

The European avalanche danger scale, set by the EAWS (the European Avalanche Warning Services), runs from 1 to 5. It is the standard used by every avalanche forecasting service in Europe. What each level means in practice, not just the label, is the basis of every route decision.

Level 1, low. Generally favourable conditions. Natural avalanches are unlikely. Human-triggered avalanches are possible only on isolated, very steep extreme terrain. At this level you can be more flexible with route choice, but never assume zero risk. Isolated pockets of instability can still exist, especially on north-facing aspects or near ridgelines with wind-loaded snow.

Level 2, moderate. Mostly favourable conditions. Avalanche hazard is elevated on specific steep slopes as described in the bulletin. Careful route selection on the indicated aspects and elevations is necessary. Do not read "moderate" as "no danger": in Switzerland, about 30% of avalanche deaths happen at level 2 (SLF).

Level 3, considerable. This is the critical level. Dangerous conditions exist on many steep slopes. Natural avalanches are possible. Human-triggered avalanches are likely on the specific terrain described in the bulletin. Experienced terrain assessment is required. You must avoid the aspects, elevations, and terrain features described in the bulletin.

In Switzerland about half of all avalanche deaths happen at level 3 (SLF). In terms of risk it is not the middle of the scale: conditions are dangerous enough to kill, but not so obvious that everyone stays home.

Level 4, high. Very dangerous conditions. Natural avalanches are likely, including large ones. Human-triggered avalanches are likely on many steep slopes. At level 4 the services advise moderately steep terrain only, and out of the runouts of the steeper slopes above.

Level 5, very high. Extraordinary avalanche conditions. Widespread natural avalanches expected, even on moderate slopes. Avoid all avalanche terrain. This rating is rare; it typically follows extreme snowfall events or rapid warming after major storms. When you see level 5, stay in the resort or stay home.

A critical nuance: the danger level can vary within a single bulletin region depending on aspect and elevation. The bulletin might rate the overall danger as 3, but specify that north-facing slopes above 2,400 m are where the real hazard is concentrated. The number alone does not tell you this. The details do.

The five avalanche problem types

The EAWS defines five standard avalanche problem types. These tell you what kind of avalanche threat exists, not just how much. Each problem type has different triggers, affects different terrain, and requires different risk management strategies. The bulletin will tell you which problems are active, where they are, and how sensitive they are to triggering.

New snow

Fresh snowfall loads slopes with additional weight that the existing snowpack may not be able to support. New snow problems can manifest as loose snow avalanches (sluffs) on steep terrain or as slab avalanches when the new snow bonds poorly to the old surface.

This is the most intuitive avalanche problem: heavy snowfall means higher danger. The key variables are the amount of new snow, the rate of accumulation, temperature during snowfall, and wind. Cold, dry snow falling without wind bonds poorly. Warm, wet snow or wind-affected snow can create slabs quickly.

Management: wait until the new snow has bonded, or choose sheltered, low-angle terrain. The bulletin says how fast the new snow is bonding; cold keeps a new-snow problem alive longer. It also says how much new snow has fallen and where the danger is concentrated.

Wind slab

Wind transports snow from windward slopes and deposits it on lee slopes, forming cohesive slabs that can be triggered by a skier. Wind slabs can form even without new snowfall: existing surface snow gets picked up and redeposited. A slope that was fine yesterday can be loaded overnight if the wind changes.

Wind slabs are often recognizable: look for pillow-shaped deposits on lee aspects, shooting cracks when you cross a slope, and hollow-sounding snow underfoot. They tend to form near ridgelines, behind terrain features, and in gullies that channel wind.

Management: identify the wind direction from the bulletin and from field observations (flagged trees, sastrugi, cornices). Avoid lee aspects at the elevations where wind transport has been active. If the bulletin says "strong northwest winds above 2,500 m," south-to-east-facing slopes above 2,500 m near ridgelines are where wind slabs will be.

Persistent weak layer

This is the avalanche problem that catches experienced riders most often. A weak layer buried deep in the snowpack, often formed by faceting during cold, clear weather, lies beneath a strong surface that feels and looks stable. You can ski on it for days without incident, and then someone triggers a large slab that breaks on the buried weak layer.

Persistent weak layer problems produce the largest and most destructive avalanches. The slab can be thick and heavy, propagating over long distances. The surface gives no sign of it.

The bulletin will describe persistent weak layers explicitly. Pay close attention when you see this problem type listed. It means the danger may not be obvious in the field, and that standard stability tests on the surface may not detect the buried weakness. This is the problem type that demands the most conservative decision-making.

Management: when persistent weak layers are active, terrain avoidance is the primary tool. Stay on terrain below 30° and out from under steeper slopes, avoid the aspects and elevations described in the bulletin, and do not trust the feeling of stability underfoot. Travel one at a time on suspect slopes. Consider choosing entirely different terrain.

Wet snow

Water weakens the bonds between snow grains. When the snowpack gets wet from rain, warm temperatures or strong sun, it loses strength rapidly. Wet snow avalanches can be loose (point releases that fan out) or slabs, and they tend to be heavy and destructive despite sometimes moving slowly.

You can often anticipate when they will occur based on the weather forecast, the time of day, and the aspect. East-facing slopes warm first in the morning, south-facing slopes around midday and west-facing slopes in the afternoon. North-facing slopes are the last to be affected.

Management: plan early starts. Be on south-facing slopes before the sun softens them and descend before afternoon warming makes them dangerous. Watch for roller balls and pinwheels on the surface: these are early signs that the snowpack is losing strength. If the snow is getting wet and heavy underfoot, the slope is past its time.

Gliding snow

Gliding snow occurs when the entire snowpack slides slowly on smooth ground, typically rock slabs or steep grass slopes. The visible sign is glide cracks: large, gaping fissures in the snow that reveal the ground underneath. Glide avalanches release when the friction between the snowpack and the ground drops below a critical threshold.

The timing of a glide release cannot be predicted. A glide crack can open and sit there for weeks before releasing, or it can release within hours.

Management: avoid terrain below visible glide cracks. Do not stop, rest, or transition below them. Do not ski under glide cracks even if they have been there for days. The bulletin will mention gliding snow when it is a concern; what counts is to look at the terrain yourself and keep out of the areas directly below any cracks you see.

Reading the danger rose

The danger rose (also called the aspect-elevation diagram) is one of the most information-dense elements of the avalanche bulletin. It is a circular diagram that tells you exactly which aspects (compass directions) and elevations are dangerous. Learning to read it quickly and correctly is essential.

The outer ring of the rose shows the eight compass directions: N, NE, E, SE, S, SW, W, NW. The diagram is divided into elevation bands, typically two or three zones around the treeline or a specific altitude (for example above and below 2,200 m). Shaded or coloured sectors indicate dangerous combinations of aspect and elevation.

The danger rose is an AND: the marked danger applies where aspect AND elevation AND slope steepness overlap. If the rose marks north-to-east aspects above 2,200 m, that is where the problem is expected. Outside the marked sectors the danger is lower, not zero; SLF treats it as about one level lower, and the runouts of the marked slopes still reach the terrain below them.

An example: level 3, with N, NE and E above 2,400 m marked. A north-facing slope at 2,600 m and an east-facing slope at 2,800 m are in the marked sectors. Slopes outside the marked sectors carry a lower danger; slope angle and the runouts under steeper terrain still count.

One more nuance: the danger rose shows the most likely danger zones, not the only possible ones. Conditions are not binary at the boundary lines. A slope at 2,350 m on a north aspect is not out of danger just because the bulletin draws the line at 2,400 m. Use the rose as guidance, not as a guarantee, and keep a margin.

From bulletin to route decision

Reading the bulletin is only useful if you translate it into route decisions. Here is a step-by-step workflow for turning the bulletin into a plan for the day.

Step 1: Read the danger level and overall assessment. Get the big picture. Is this a day for ambitious objectives or conservative terrain choices? At level 1-2 with no persistent weak layers, you have more freedom. At level 3 or above, your terrain options are limited from the start.

Step 2: Identify the avalanche problems for today. What type of threat are you dealing with? New snow and wind slab problems are relatively intuitive to manage. Persistent weak layers demand extra caution. Wet snow problems require careful timing. Each problem type shapes your strategy differently.

Step 3: Check the danger rose. Which aspects and elevations are affected? Mark these on your mental map. These are the zones you need to avoid or approach with extreme caution.

Step 4: Look at your planned route on a map. Does it cross the dangerous zones identified by the danger rose? Check the slope angles along your route, particularly from 30 degrees up. On the BEYOND map the danger level, with its critical aspects and elevations, is drawn on the 3D terrain next to the slope angle layer, so you can see which slopes on your route the bulletin is talking about. Remember that danger zones include not just the slopes you plan to ski, but also the slopes above your skin track and above your transition zones.

Step 5: Consider alternatives. If your planned route crosses dangerous terrain, look for options on different aspects, at lower elevations, or in an entirely different area. Having a Plan B and Plan C before you leave the car is essential.

Step 6: Check the trend. Is the danger rising or falling over the coming days? A falling trend means conditions are stabilizing. A rising trend, especially with incoming weather or warming, means you should be more conservative, not less.

Step 7: Plan your timeline. If wet snow is a problem, plan an early start and a deadline for when you need to be off steep south-facing slopes. If new snow is falling overnight, factor in reduced visibility and fresh loading.

Finally, plan in rounds: the bulletin is a forecast; what you see on the day overrides it. Continuously reassess throughout the day. If you see signs of instability (recent avalanche activity, shooting cracks, collapsing or whumpfing), the conditions are worse than the bulletin suggested and you need to adjust immediately.

Where to find avalanche bulletins

Every major Alpine country publishes avalanche bulletins through its national or regional avalanche service. Here are the primary sources:

Switzerland: the SLF (WSL Institute for Snow and Avalanche Research) publishes the bulletin at slf.ch and in the White Risk app. In winter it comes out every day at 17:00 and is valid until 17:00 the next day; when the danger is level 3 or higher anywhere in Switzerland, the SLF also publishes an update at 08:00.

Austria: for Tyrol, avalanche.report (the Euregio service it shares with South Tyrol and Trentino) publishes at 17:00 for the period until 17:00 the next day. The other Austrian states (Vorarlberg, Salzburg, Carinthia, Styria and others) publish their own bulletins through their Lawinenwarndienst.

France: Météo-France publishes a BERA (Bulletin d'Estimation du Risque d'Avalanche) for each mountain massif in the Alps, the Pyrenees and Corsica. It is written in the afternoon (the bulletins we checked say 16:00) for the next day.

Italy: the regional services, organised in AINEVA, publish per region; South Tyrol and Trentino are in avalanche.report.

BEYOND draws the danger level from the European warning services on the slopes in the map. For Switzerland (SLF), Tyrol (avalanche.report) and France (Météo-France) this website also has a page per region: on our avalanche bulletins page you can search a region and see its danger level and avalanche problems, with a link to the full bulletin at the source. Examples: Kandersteg and Zermatt (SLF), Kalkkögel in Tyrol (avalanche.report) and Mont-Blanc (Météo-France).

Common mistakes

Even experienced backcountry skiers fall into patterns that undermine good bulletin use. Here are the most common mistakes and how to avoid them.

Only looking at the danger number. The number is a summary: it condenses complex, spatially variable conditions into a single digit. Two days at level 3 can be completely different depending on the avalanche problems, the affected aspects, and the elevation bands. Read the full bulletin every time.

Treating level 2 as "no danger". "Moderate" sounds reassuring, but it is not a green light: level 2 means the hazard is elevated on specific slopes, and in Switzerland about 30% of avalanche deaths happen at this level. The terrain the bulletin describes as dangerous at level 2 is dangerous.

Not reading the avalanche problems. Knowing that the danger is level 3 tells you the magnitude. Knowing that the problem is persistent weak layers tells you the nature of the threat, and persistent weak layers require completely different management than new snow or wind slabs. The "what" matters as much as the "how much."

Ignoring the danger rose. The rose tells you exactly where the danger is concentrated. If you do not check which aspects and elevations are affected, you are flying blind. When the rose marks north-facing slopes above 2,500 m, a south-facing slope at 2,000 m is outside that rose: lower danger there, not none.

Not adjusting plans when field observations differ from the forecast. The bulletin is a regional forecast, not a slope-by-slope guarantee. If you observe signs of instability that the bulletin did not predict (recent avalanche activity, whumpfing, shooting cracks), the conditions are worse than forecast and you need to choose more conservative terrain immediately.

Forgetting that the bulletin is regional. Avalanche conditions vary locally. A south-facing slope sheltered from the wind may be more stable than the bulletin suggests. A specific gully that funnels wind may be more dangerous. The bulletin gives you the framework; your field observations fill in the local details.