Date issued

Dec 22, 2017 - 8:05 AM

Valid until

Dec 23, 2017 - 8:00 AM

Prepared by

mark herbison

A surface hoar layer is buried by 40cm of settling snow and could become increasingly reactive.

Take the time to evaluate the snowpack as you transition into avalanche terrain,  pay attention to cracking and settlements in your surrounding area.

Regular season
Thursday - December 21, 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

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.

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.

Friday - December 22, 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

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.

Saturday - December 23, 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. Expect the slab to be increasingly sensitivity as you transition into steep and/or wind effected terrain. Solar aspects harbor a thin crust layer below the slab and a facet surface hoar combo BTL.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • Watch for whumpfing, hollow sounds, and shooting cracks.

Avalanche Problem 2: Wind Slabs

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

20-40km/hr N-NE winds are forming reverse loaded wind slab in wind exposed areas at and above tree line. These slabs may have surface hoar or crust underneath leading them to be sensitive to human triggering.

Travel and Terrain Advice
  • Watch for signs of instability such as whumpfing, or cracking.
  • Keep an eye out for reverse loading created by N-NE winds.

Avalanche Summary

Numerous natural avalanches over the past few days up to sz 2.5 from steep terrain.

The surface hoar layer at tree line and below will become increasingly reactive as the storm snow settles into more of a cohesive slab. Be aware of this when traveling in steeper, open areas or where a slab exists.

Snowpack Summary

50cm of settling snow sits on the Dec 15 surface hoar, persistent weak layer. On steeper solar aspects this layer is a crust and/or a crust with small surface hoar on top. The crust runs up into the alpine on steep south and west aspects. Deeper in the snowpack there are a series of crust layers that are currently bonding well.

Weather Forecast

A ridge of high pressure will build throughout the day bringing sun but no snow. The winds will be from the North in the15-40km/hr range with an Alpine high of -17... bbrrr thats cold!! The clear skies and cold temps will continue over the weekend and into early next week. No snow in the 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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