Avalanche Forecast

South Coast

Date issued

Feb 12, 2018 - 5:32 PM

Valid until

Feb 13, 2018 - 2:00 PM

Prepared by

cgarritty

Maintain elevated caution around areas where wind loading has occurred. Small avalanches can have big consequences around cliffs and other terrain traps.

Regular season
Monday - February 12, 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

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 - February 13, 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.

Wednesday - February 14, 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

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?

Wind slabs may have a poor bond to the underlying crust and be reactive at upper alpine elevations. Recent shifting winds may have formed new slabs on a wide range of aspects. Loose dry avalanches are possible from steep alpine terrain features.

Travel and Terrain Advice
  • Use caution above cliffs where small avalanches may have severe consequences.
  • Be careful with wind loaded pockets that may exist near ridge crests and roll-overs.

Avalanche Problem 2: Cornices

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

Large cornices have formed and may remain fragile. Cornices are inherently unstable, unpredictable, and demand respect. Give them a wide berth from above and below.

Travel and Terrain Advice
  • Give cornices a wide berth when traveling on or below ridges.
  • Firm cornices may pull back into flat terrain at ridgetop if they fail.

Avalanche Summary

On Saturday, a cornice collapse was the likely cause of a size 2 avalanche on a north facing slope near the West Lion. See here for images and more details.

Pockets of thin wind slab may exist in wind-loaded areas in the high alpine and may be sensitive to human triggers.

Snowpack Summary

Rain at the end of the week saturated snow surfaces and only higher alpine elevations were lucky enough to receive a light cover of new snow. With the arrival of cold temperatures, the upper snowpack has locked up as a firm crust. Where new snow exists above the crust, it has been redistributed by recent strong southwest winds. The average snowpack depth at treeline is 300 cm of well settled snow with no significant layers of concern.

Weather Forecast

Tuesday: Cloudy with flurries beginning late in the day and bringing 10-15 cm of new snow by Wednesday morning. Moderate to strong southwest winds. Freezing level dropping to 500 metres as the temperature inversion breaks down. Alpine high temperatures of -4.

Wednesday: A mix of sun and cloud. Light north winds. Freezing level to 700 metres with alpine high temperatures of -2.

Thursday: Mainly cloudy with flurries increasing over the day and bringing approximately 15 cm of new snow by Friday morning. Light southwest winds increasing over the day and overnight. Freezing level to 600 metres with alpine temperatures of -3.

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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