Avalanche Forecast

South Rockies

Date issued

Nov 30, 2017 - 4:52 PM

Valid until

Dec 1, 2017 - 2:00 PM

Prepared by

swerner

The snowpack remains highly variable with few reports from the region. Reactive wind slabs may exist at upper elevations, as well as several deeper weak layers buried in the snowpack. Use a conservative approach and terrain selection.

Regular season
Friday - December 1, 2017
Alpine

3 - Considerable

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.

Treeline

2 - Moderate

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.

Below Treeline

1 - Low

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.

Saturday - December 2, 2017
Alpine

3 - Considerable

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.

Treeline

2 - Moderate

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.

Below Treeline

1 - Low

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.

Sunday - December 3, 2017
Alpine

3 - Considerable

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.

Treeline

2 - Moderate

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.

Below Treeline

1 - Low

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.

Avalanche Problem 1: Wind Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Stiff wind slabs could be reactive to rider triggers at treeline and above on lee and cross-loaded slopes.

Travel and Terrain Advice
  • Use caution in lee areas. New snow and wind loading have created wind slabs.
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Persistent Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

There are several crusts now buried within the snowpack. Be extra caution in thin snowpack areas where it may be possible to trigger a deeper layer and assume that a release near the surface may also have the potential to step-down to a deeper layer.

Travel and Terrain Advice
  • Be aware of thin areas that may propogate to deeper instabilites.

Avalanche Summary

No recent avalanches have been reported from the region. On November 29th a slab avalanche was reported from Kananaskis Country from Mt. Lawson and was possibly triggered by cornice fall. Please post your observations to the Mountain Information Network

Snowpack Summary

There remains to be very little information regarding snowpack structure within the region. I suspect that the upper snowpack consists of 10-50 cm of recent storm snow above a series of crusts, the most recent being the November 26 crust which is likely to be found up to 2550m elevation and approximately 2-5 cm thick. Below this is a thin layer of low density snow then the November 23 crust which also suspected to exist near 2450 m elevation. A third crust from late October (October 31) can likely be found down approximately 40-60 cm. This October 31 "crust/facet combo" (sugary snow) has been identified as a failure layer in recent avalanche reports from the Kananaskis area to the north will likely remain a concern for northern regions of the South Rockies. Finally the early season early October rain crust lies near the base of the snowpack bringing the average snowpack depths at upper elevations 60-110 cm. Take into account that the snowpack is highly variable in regards to aspect and elevation.

Weather Forecast

Friday: Mainly cloudy with isolated flurries. Moderate to strong ridgetop winds from the West. Alpine temperatures near -10 and freezing levels near 1000 m.

Saturday: Mostly cloudy with isolated flurries. Moderate ridgetop winds from the South West. Alpine temperatures near -8 and freezing levels 1100 m.

Sunday: Cloudy with 3-7 cm of new snow. Light ridgetop winds from the North West.

Local snow fall amounts may be enhanced in the southern part of the region. Check out the Mountain Weather Forecast.

Danger Ratings Explained

1 - Low

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.

2 - Moderate

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.

3 - Considerable

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.

4 - High

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.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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