Avalanche Forecast

South Coast

Date issued

Feb 25, 2018 - 4:53 PM

Valid until

Feb 26, 2018 - 2:00 PM

Prepared by

ghelgeson

Storm slabs up to 55 cm in depth may remain problematic Monday. Choose wind sheltered terrain features while minimizing exposure to both cornices and overhead avalanche paths, the morning sun could initiate natural avalanches.

Regular season
Sunday - February 25, 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.

Monday - February 26, 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.

Tuesday - February 27, 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

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

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.

Avalanche Problem 1: Storm Slabs

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

Up to 55 cm of recent storm snow rests on old wind slabs that are not bonding well to a buried crust. Storm snow may remain sensitive to human triggering Monday and  will likely need another day to settle and stabilize.

Travel and Terrain Advice
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.
  • Use ridges or ribs to avoid pockets of wind-loaded snow.
  • Start with small terrain features and gather information before committing to bigger objectives.

Avalanche Problem 2: Cornices

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

Large cornices have formed along ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially if the sun is shining.

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

No new activity to report from Saturday. The new snow was reactive to skier activity on Friday, producing small (size 1) dry loose and storm slabs. See this MIN report that talks about storm slabs 10 to 40 cm in depth here.

Snowpack Summary

Around 30 to 40 cm of storm snow fell on Friday and another 10 to 15 cm of snow fell Saturday night into Sunday. Both of these storms had strong southerly winds. All of this snow fell on previously wind-affected surfaces and a sun crust on southerly aspects. The new snow may not bond well to these surfaces and could be reactive to both natural and human triggers.

A hard rain crust that extends into alpine terrain is buried about 60 to 100 cm. Reports suggest the snow has a poor bond to the crust with test results showing sudden planar characteristics and a Rutschblock 2 (the whole block failing after standing on it).

Monitor the bonds of the new snow as well as the bond of the snow directly above the buried crust. There are no substantial layers of concern below the crust.

Also make note of cornices at ridgeline. Variable winds in the past month have produced cornices on all aspects. They will become touchier as they grow in size, as temperatures rise, and as the sun packs a strong punch on clear days. Stand well back of them!

Weather Forecast

The work week kicks off with a rather disorganized pattern that is not expected to generate any significant snowfall, but a significant change looks to be in store as a vigorous low approaches the South Coast region Wednesday afternoon.

MONDAY: Clear skies in the morning, a few clouds building in the afternoon, freezing level around 500 m, light west/northwest wind, no significant snowfall expected.

TUESDAY: Broken cloud cover with clearing in the afternoon, freezing level around 900 m, moderate to strong west/northwest wind, trace of snow possible.

WEDNESDAY: Overcast, freezing level around 700 m, potentially strong to extreme south/southwest wind, copious amounts of precipitation possible, but the latest model run shows about 15 cm of snow. Stay tuned for more details.

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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