Date issued

Dec 30, 2017 - 8:10 AM

Valid until

Dec 31, 2017 - 8:00 AM

Prepared by

ian gale

With the addition of last night's new snow, careful evaluation of the December 15 surface hoar layer should be a part of your decision making process.

Regular season
Saturday - December 30, 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.

Sunday - December 31, 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.

Monday - January 1, 2018
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.

Avalanche Problem 1: Storm Slabs

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

The 30cms of recent storm snow will remain touchy for loose avalanches in steep terrain. With all the available fetch, strong Northerly winds will have created soft slabs on lee slopes.  Avalanches will have the potential to reach runouts today.

Travel and Terrain Advice
  • Avoid travelling on ledges and cliffs where sluffing may have severe consequences.

Avalanche Problem 2: Persistent Slabs

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

The December 15 surface hoar layer is widespread around treeline and buried 60cm. Cold temps have kept the slab from gaining cohesion, but it may be reactive on steep unsupported and/or wind affected terrain.

Travel and Terrain Advice
  • Dig down to find and test weak layers before committing to a line.
  • Watch for signs of slab formation, such as whumpfing and shooting cracks.

Avalanche Summary

We experienced a widespread natural avalanche cycle yesterday. Numerous loose dry and storm slab avalanches ran to sz 2.5, mostly from steep terrain. Expect this cycle to continue today with avalanches having the potential to reach out into runout zones.  Be aware of naturals from above especially in areas like Connaught Creek

Snowpack Summary

25cm of low density new snow fell in the last 36 hrs while temps remained quite cold. An isolated surface hoar/ facet layer (December 27) is buried down 20cm. The Dec 15 surface hoar/sun crust layer, which is widespread at treeline, is buried down 60cms. Cold temperatures have hindered slab development in the upper snowpack.

Weather Forecast

After last nights underwhelming storm we'll see another few cms out of the system as it leaves the province. Today will be mostly cloudy with some sunny periods but will remain cold with freezing level firmly at valley bottom.  Winds will ease and become light westerly.  An Arctic ridge will rebuild Sunday and bring back the sunny weather.

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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