Date issued

Dec 24, 2017 - 8:00 AM

Valid until

Dec 25, 2017 - 8:00 AM

Prepared by

mark herbison

Large avalanches are possible in isolated terrain features (couloirs, steep faces, etc). Evaluate the snowpack thoroughly before entering your line.

Regular season
Sunday - December 24, 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

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.

Monday - December 25, 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

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.

Tuesday - December 26, 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

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.

Avalanche Problem 1: Persistent Slabs

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

Recent storm snow is settling into a persistent slab which sits on the Dec 15 surface hoar. Expect the slab to be more sensitive as you transition into steep and/or wind effected terrain. Solar aspects have a thin crust layer below the slab.

Travel and Terrain Advice
  • Watch for whumpfing, hollow sounds, and shooting cracks.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Avalanche Problem 2: Wind Slabs

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

15-35km/hr variable winds are forming pockets of wind slab in exposed areas in the alpine and at tree line. These slabs may have surface hoar or crust underneath, leading them to be sensitive to human triggering.

Travel and Terrain Advice
  • Variable winds have created pockets of wind slab on all aspects.
  • Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.

Avalanche Summary

No new avalanches observed yesterday.

Numerous natural avalanches from a few days ago up to sz 2.5 in steep terrain.

Snowpack Summary

50 cm of low density snow redistributed by variable winds in the alpine and tree line forming pockets of wind slab. Below tree line the storm snow remains unconsolidated and sits on the Dec 15 surface hoar which is widespread and largest where sheltered. In the alpine, Dec 15 is a thin crust on solar aspects and small surface hoar on polar aspects.

Weather Forecast

A strong ridge of high pressure is sitting over the region giving us clear sunny skies. The winds will be from the north in the 15-35km/hr range with an Alpine high of -17... bbrrr thats cold, bring an extra layer or two! The ridge of high pressure looks like it will persist until mid week, with no snow in the forecast until  Wednesday.

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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