Avalanche Forecast

South Rockies

Date issued

Dec 3, 2017 - 4:31 PM

Valid until

Dec 4, 2017 - 2:00 PM

Prepared by

swerner

Pockets of reactive wind slab may exist on northeasterly aspects.

Regular season
Sunday - December 3, 2017
Alpine

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.

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.

Monday - December 4, 2017
Alpine

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.

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.

Tuesday - December 5, 2017
Alpine

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.

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 in the alpine on leeward and cross-loaded slopes.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Watch for whumpfing, hollow sounds, and shooting cracks.

Avalanche Problem 2: Persistent Slabs

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

There are several crusts now buried within the snowpack. Use extra caution in thin snowpack areas where it may be possible to trigger a deeper layer. Triggering a wind slab 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.
  • If triggered wind slabs may step down to deeper layers resulting in large avalanches.

Avalanche Summary

No new avalanches have been reported from this region. There is potential for triggering wind slabs on leeward slopes and dry loose avalanches from steeper terrain features. Smaller avalanches may step down and trigger larger avalanches on buried weak layers deeper in the snowpack. Please submit your observations this weekend to the Mountain Information Network.

Snowpack Summary

The snowpack remains highly variable with very little information regarding snowpack structure within the region. Average snowpack depths at upper elevations range from 60-110 cm with scoured snow surfaces on southwesterly slopes and deeper pockets of wind slab on northeasterly slopes. Below the surface exists a series of crusts that were buried near the end of November approximately 40 cm and 70 cm down. Deeper in the snowpack a third crust from the end of October exists as a "facet/crust" combo and has been identified as a potential sliding interface where snowpack testing North of the region (Kananaskis Country) is proving hard but sudden collapse results.

Weather Forecast

Monday: Mix of sun and cloud. Alpine temperatures -10. Ridgetop winds light from the west.

Tuesday: A mix of sun and cloud. Alpine temperatures -4 and freezing levels 1200 m. Ridgetop winds light with strong gust from the northwest

Wednesday: Mostly sunny. Alpine temperatures plus 1 degree and freezing levels near 1500 m. Ridgetop winds light-moderate from the northwest.

Expect strong alpine temperature inversions starting Wednesday. For more detail please check 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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