Avalanche Awareness: Part 6: Understanding Avalanche Danger Ratings and Why “Moderate” Isn’t Safe

In the first part of this 7-part course on avalanche safety, we explored the types of avalanches, their causes, and the risks they pose. In the second section, we covered essential avalanche equipment, emphasising the importance of preparation and practice. The third and fourth parts focused on recognising avalanche-prone terrain and conducting field observations and snowpack tests to assess stability. Most recently, the fifth section explained how weather influences avalanche risk, providing insights into how snowfall, wind, and temperature changes interact with the snowpack.

Missed Part 5? Click here

Now, in this sixth part, we turn our attention to avalanche bulletins—your most important tool for planning a backcountry trip. These bulletins provide a snapshot of current conditions, potential hazards, and recommendations for safe travel. However, simply glancing at a danger rating isn’t enough. It’s essential to understand what these ratings mean, how to interpret the details within the bulletin, and why levels like "Moderate" (Level 2) and "Considerable" (Level 3) require careful planning and vigilance.

Many accidents occur because people misinterpret or underestimate the risks at these levels. This section will help you decode avalanche bulletins, understand their recommendations, and apply that knowledge to make safer decisions in the backcountry. Let’s dive in!

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The Avalanche Danger Scale: What Each Level Means

The European Avalanche Danger Scale (widely used, including by Météo France) has five levels, each describing the likelihood of avalanches, the type of activity likely to trigger them, and the precautions necessary:

1. Low (Level 1):
• Description: The snowpack is generally stable. Natural avalanches are unlikely, and human-triggered avalanches are rare.
• Precautions: While risk is minimal, avalanches can still occur in isolated areas, such as steep, extreme terrain. Always carry your safety gear.
2. Moderate (Level 2):
• Description: The snowpack is mostly stable, but avalanches can be triggered on specific steep slopes, especially by a skier, snowboarder, or climber.
• Key Danger Zones: Terrain over 30° with recent wind loading, fresh snow, or buried weak layers.
• Why It’s Risky:
• Many people associate "Moderate" with "safe," leading to overconfidence.
• Triggering avalanches at this level often requires less force than expected.
• Statistically, many avalanche accidents occur at this danger level, especially when conditions are localized or poorly understood.
• Precautions: Stick to low-angle terrain (less than 30°) and avoid slopes with visible red flags (e.g., wind slabs, cracks, or recent avalanches).
3. Considerable (Level 3):
• Description: The snowpack is unstable in many places. Avalanches are likely on steep slopes and can be triggered by a single skier, climber, or snowboarder. Some natural avalanches may occur.
• Key Danger Zones: Steep slopes (30°–45°), especially those with wind slabs, recent snowfall, or weak layers.
• Why It’s Risky:
• This is the most dangerous level for backcountry users because the risk is widespread, yet many people still venture out.
• Poor route choices or ignoring red flags can lead to large, destructive avalanches.
• Precautions: Stick to well-defined safe zones, avoid steep terrain, and reconsider your trip if conditions don’t allow safe alternatives.
4. High (Level 4):
• Description: The snowpack is very unstable. Avalanches are likely to occur naturally and can be easily triggered by human activity. Large, destructive avalanches are possible.
• Key Danger Zones: Most slopes steeper than 30°.
• Why It’s Risky:
• Natural avalanches are widespread. Travel in avalanche terrain is extremely dangerous.
• Precautions: Avoid avalanche terrain entirely. Stick to flat, safe zones far from avalanche paths or runouts.
5. Very High (Level 5):
• Description: The snowpack is extremely unstable. Large natural avalanches are certain, even on moderately steep terrain.
• Key Danger Zones: All avalanche terrain.
• Precautions: Do not travel in avalanche terrain under any circumstances.

Why Most Accidents Happen at Moderate (Level 2) or Considerable (Level 3)

1. Perceived Safety at Moderate (Level 2):

• At "Moderate," people often think the risk is minimal and let their guard down. However, the risk is localised, meaning avalanches are likely on specific slopes with weak layers or triggers (like wind slabs or buried hoar).
• Without a deep understanding of snowpack conditions and terrain features, travellers may unknowingly enter these dangerous zones.

2. Widespread Instability at Considerable (Level 3):

• "Considerable" is where the danger becomes more widespread, but the terrain may still appear deceptively stable in some areas.
• Many avalanches at this level are triggered by human activity. Groups may venture into steep terrain assuming it's safe because they haven't directly observed warning signs.

3. Common Cognitive Biases:

• Overconfidence: Skiers and climbers may assume their skill level reduces the risk, forgetting that avalanches don’t discriminate based on experience.
• Heuristic Traps: Groupthink or "powder fever" (the excitement of fresh snow) can lead people to ignore danger signs or warnings.

How to Read and Follow Avalanche Bulletins

Key Sections of the Bulletin:

1. Danger Rating: The overall level of danger for the region. Pay attention to how it’s distributed by elevation and slope aspect.
2. Snowpack Summary: Details about weak layers, recent wind slabs, or persistent instability in the snowpack.
3. Travel Advice: Specific recommendations, such as avoiding slopes over 30° or sticking to certain elevations.
4. Recent Avalanche Activity: Reports of natural or human-triggered avalanches, which indicate real-time instability.

What You Should Do:

• Plan Accordingly: Use the bulletin to choose terrain that avoids danger zones (e.g., low-angle slopes or densely forested areas).
• Stay Flexible: If the bulletin suggests elevated risk, adjust your objectives or postpone your trip.
• Combine With Observations: A bulletin is a regional summary—always confirm conditions in the field by watching for red flags (e.g., cracks, whumpfing, or recent slides).

Practical Example of Reading the Avalanche Bulletin

You’re planning a ski tour in Chamonix, and the bulletin for your area reads:

• Danger Level: Moderate (Level 2) below 2,000 m; Considerable (Level 3) above 2,000 m.
• Key Hazards: Wind slabs on north and east-facing slopes, especially above 30°. Persistent weak layers noted on south-facing slopes from recent warming.
• Recommendations: Avoid steep terrain above 2,000 m, particularly leeward slopes.

Your Interpretation:

• You plan your route to stick to south-facing, low-angle slopes below 2,000 m.
• You check the weather forecast for wind direction and confirm observations of wind slabs in the field before committing to steeper terrain.

Key Takeaway

Moderate (Level 2) and Considerable (Level 3) danger ratings do not mean "safe." Most avalanche accidents occur at these levels because people misjudge localised risks or ignore red flags. Always treat the danger level as a guide to inform your route planning, stay alert in the field, and prioritise safety over objectives.

Ready to follow onto the next lesson? Click here for chapter 7 - Best Practices for Avalanche Safety