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Avalanche Forecast - Purcells    


Date Issued   Saturday, 21 January 2012 6:34 PM      Valid Until    Sunday, 22 January 2012 4:00 PM
Danger Rating: Sunday Alpine Treeline Below Treeline
3 - Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding and conservative decision making essential.
3 - Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding and conservative decision making essential.
2 - Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Monday Tuesday
Alpine 3 - Considerable 3 - Considerable
Treeline 2 - Moderate 3 - Considerable
Below Treeline 2 - Moderate 2 - Moderate
Confidence: Fair - Due to variable snopack conditions
Learn more about danger ratings
Low Moderate Considerable High Extreme

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

Wind Slabs
What Elevation Zone?
Which Slopes?
Chance of Avalanches?
Expected Size?
Moderate winds from saturday will have created touchy windslabs on lee features at higher elevations.
Travel and Terrain Advice
  • The new snow will requires several days to settle and stabilize.
  • Be cautious as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.
Storm Slabs
What Elevation Zone?
Which Slopes?
Chance of Avalanches?
Expected Size?
A classic recipe for storm slabs has evolved; particularly on the west side of the range: new snow falling with rising temperatures onto loose dry snow. Watch for deeper storm slab avalanches, especially in steep or convex terrain.
Travel and Terrain Advice
  • The new snow will requires several days to settle and stabilize.
  • Be cautious as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.
Persistent Slabs
What Elevation Zone?
Which Slopes?
Chance of Avalanches?
Expected Size?
Two layers to watch: 1. Buried surface hoar, most likely triggered on steep, unsupported slopes amongst the trees. 2. Basal facets, triggerable from thin snowpack areas or by a very heavy load (cornice fall, airborne sled). Avalanches could be large.
Travel and Terrain Advice
  • The new snow will requires several days to settle and stabilize.
  • Be cautious as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.

Prepared by jlammers