Ask these questions during tour planning, at the time of actual route selection on the day of the tour, and when traversing individual slopes during a tour.
Check the three key factors that affect avalanche risk, snow+weather, terrain, people, at every step asking at least the questions in the table below. The answers to these questions and your own competence and knowledge determines your decisions.
There is no absolute standard. What might be safe for a highly skilled group that takes every precaution and modifies its behaviour and route according to the risks would be absolute folly for an inexperienced group quite unable to do this.
If in doubt, assume the worst case.
There is no such thing as zero risk. Hoar frost and graupel layers can persist in the snowpack all winter long with a correspondingly high slab avalanche risk throughout the winter even though all other factors might suggest otherwise. Check.
Route Selection Checklist
| Snowpack/Weather | Terrain | People | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tour planningPlan in checkpoints and alternatives. | Avalanche Bulletin. Weather forecast. Information from locals. |
1:25,000 Map. Gradients from map Guide books. Photos. Own knowledge. |
Size of group ? Motivations? Expectations? Skill level? Equipment. Who responsible? |
||||||||||
| Route selectionUse checkpoints and alternatives. | Avalanche Bulletin Risk Factor and type of risk. First day after new snow? Fresh snow still on the trees? Temperature? Actual snow conditions. WUMM sounds? Wind direction? Drifting? Avalanches? Oddities. Visibility. |
Check terrain on sight. Gradient. Terrain traps. Existing ski tracks -how many? How old? Orientation, steepness of risk slopes. Reports from others. |
Who’s in my group? Competitive atmosphere? Time plan for tour? Itinerary left with someone? Backmarker. Appoint possible search leaders and stress need for discipline. Check all transceivers transmitting before leaving the hut/car. |
||||||||||
| Individual slopes during the tourGo / No Go | How much new snow? Signs of wind? Lee or windward? Visibility? Solar radiation? Temperature? Snowpack stability? Possible slab risk? Alarm signs? |
Actual gradient? Steepest part of slope?
At factor 3 limit route to 30° slopes maximum. |
How many people on the slope? Do not be pressured by presence of other groups. Group discipline? Tiredness? Technique? Spacing? Think! |
Risk Assessment Checklist
| Low risk | Some risk | Moderate risk | Considerable risk | High risk | High risk | |
|---|---|---|---|---|---|---|
| Snowfall | ||||||
| Depth of new snow | 0cm | 10cm | 20cm | 40cm | 80cm | 160cm+ |
| Time since last snow | 4 weeks | 2 weeks | 1 week | 4 days | 2 days | 1 day |
| Wind | ||||||
| Strength | No wind | Light wind | Strong wind, Heavy drifting | Storm | ||
| Lee or windward? | Windward slope | Wind dunes, Wind ripples | Lee slope | |||
| Time since last wind | 4 weeks | 2 weeks | 1 week | 4 days | 2 days | < 1 day |
| Temperature | ||||||
| during snowfall | 0° C | -2° C | -4° C | -8° C | -15° C | -25° C |
| Temperature change | Increased to 0° C for >2days | Midday, Full sun | Increased to 0°C in last hours. Föhn |
|||
| Snowpack | ||||||
| What surface below new snow | Old consolidated snow | Fine powder | Powder | Crust | Firm Ice | Loose snow, Hoar frost |
| Old snow structure | Stable fine crystal layers | Frozen snowpack (becomes wet and dangerous in sun) |
Wet ground (grass), Warm, wet snowpack | Graupel or Hoar frost between layers. | ||
| Terrain | ||||||
| Gradient of slope | <20° | <30° | >30° | > 40° | ||
| Form of slope | Flat, No bumps or gulleys | Concave, Many old ski tracks | Convex | Near crest of ridge, Gulley, Funnel | ||
| Group | ||||||
| Fully trained, Analytical, Disciplined | Other groups skiing powder nearby | Excitable, Excited, Competitive, Targets | ||||
Last updated on 1st July 2020