Date issued

Dec 23, 2017 - 4:00 PM

Valid until

Dec 24, 2017 - 4:00 PM

Prepared by

stephen holeczi

Alpine danger will be dictated by the amount of wind transport Sunday. Lots of low density snow to blow around. It looks to be another cold and sunny day.

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

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.

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 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

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.

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 26, 2017
Alpine

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.

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.

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?

Isolated wind slabs are present in the alpine, especially in lee areas.  So far reports are that these aren't yet thicker than 20cm, but pay attention to local winds as conditions can change quickly if they pick up.

Travel and Terrain Advice
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Avalanche Problem 2: Loose Dry

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

This should be come less of a problem as the winds decrease, but climbers especially should monitor wind transport in the alpine.  Avalanches haven't been running far but there is lots of snow for transport.

Avalanche Summary

A loose dry size 1.5 was observed on Rogan's Gully (Banff region) today. A piece of fresh cornice broke off from wind loading and triggered the slide. It did not go over the climb. No other natural activity was noted. This kind of observation could be very similar to areas in Little Yoho like the Field ice climbs.

Snowpack Summary

15-30cm of recent storm snow with some alpine wind effect sits over the Dec.15 layer. This weak layer consists of surface hoar (at tree-line and below), sun crust or facets (depending on location). Mod shears have been observed on this interface.

Weather Forecast

The arctic air continues Sunday through the first part of next week. Lows will be in the -20's with decreasing alpine NW winds and sunny skies.

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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