Avalanche Forecast

South Columbia

Date issued

Jan 3, 2018 - 4:36 PM

Valid until

Jan 4, 2018 - 2:00 PM

Prepared by

pgoddard

Tricky conditions warrant a conservative approach. A little warming, precipitation and/or wind-loading could be all we need to awaken a volatile persistent slab, especially at treeline.

Regular season
Wednesday - January 3, 2018
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

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.

Thursday - January 4, 2018
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

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 - January 5, 2018
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?

Warming, particularly at treeline elevations, could turn powder into slabs which can fail on persistent weak layers.

Travel and Terrain Advice
  • Use conservative route selection. Choose moderate angled and supported terrain with low consequence.
  • Watch for signs of slab formation, such as whumpfing and shooting cracks
  • Approach steep open slopes cautiously at and below treeline where buried surface hoar may exist.

Avalanche Problem 2: Loose Dry

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

Loose snow avalanches may fail with human or natural triggers at alpine elevations.

Travel and Terrain Advice
  • Choose routes that are not exposed to avalanches from above.
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Avalanche Summary

There have been a several recent reports of remote-triggered (triggered from a distance) and naturally triggered persistent slab avalanches to size 2 on all aspects between 1500-2100m. Several loose dry and a few solar-triggered loose wet avalanches have also been reported.

Reactivity of the persistent slab is likely to increase with warmer temperatures as the upper snow becomes denser.

Snowpack Summary

Warming is starting to turn dry powder into a cohesive slab in some areas. The main troublemaker in the snowpack at the moment is a layer of feathery surface hoar down 50-70 cm, buried in mid-December. In places this interface exists as a crust/facet combo. It is most prevalent around treeline, but it may be more widespread in some locations. A little more warming, precipitation and/or wind-loading could be all that is needed to turn powder into an easy-to-trigger slab above this touchy interface. It's tricky to predict and even professionals are scratching their heads a bit about exactly when and where this beast will wake up. Its a good time for conservative decision-making.

Deeper in the snowpack (about 100-140 cm down), a rain crust from November remains in the back of our minds, but it is considered dormant for now. If you have any recent observations, please share them through the Mountain Information Network.

Weather Forecast

Thursday: Increasing cloudiness, with flurries possible. A layer of warm air is expected between 2000-2500m, while it remains cold in the valleys. Light variable winds.

Friday: Cloudy with flurries. Moderate southwesterly winds.

Saturday: Light snow (5-10 cm). Light to moderate westerly winds.

More details can be found in 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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