Avalanche Forecast

South Coast Inland

Date issued

Jan 31, 2018 - 3:49 PM

Valid until

Feb 1, 2018 - 2:00 PM

Prepared by

jlammers

New snow and wind will keep the avalanche danger elevated at higher elevations on Thursday, especially in the south of the region where forecast snowfall amounts are the greatest.

Regular season
Wednesday - January 31, 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

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.

Thursday - February 1, 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.

Friday - February 2, 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.

Avalanche Problem 1: Wind Slabs

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

New snow and wind on Wednesday night are expected to form new wind slabs in higher elevation lee terrain. This new snow overlies older storm slabs which are gaining strength but may remain sensitive to human triggering in steep, unsupported terrain.

Travel and Terrain Advice
  • Be cautious as you transition into wind affected terrain.
  • Be alert to conditions that change with elevation.
  • Stay off recent wind loaded areas until the slope has had a chance to stabilize.

Avalanche Problem 2: Cornices

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

Recent heavy snowfall and strong winds have created fragile new cornices. These monsters may surprise with nasty consequences. Use extra caution around ridge crests.

Travel and Terrain Advice
  • Give cornices a wide berth when traveling on or below ridges
  • Falling cornices may trigger large avalanches on slopes below.

Avalanche Summary

On Monday 2 people were buried in a size 2 slab avalanche in Marriott Basin in the Duffey Lake area. The touring party was large and all victims were rescued successfully by their partners, but all gear was lost. Not much is known about the aspect, elevation or the weak layer associated with the avalanche.

Looking forward, new snow and wind on Wednesday night is expected to promote a new round of wind slab activity in higher elevation lee terrain.

Snowpack Summary

Monday's continuing storm brought 20-40 cm of new snow to the surface above about 1700 metres with depths that increase with elevation. The greatest accumulations occurred in the south of the region, and the snowpack at lower elevations is now capped by a new rain crust and only light new snow amounts. At higher elevations, strong southerly winds have redistributed the new snow forming deep deposits and cornices in leeward terrain. Storm snow totals since mid-January have reached about 150 cm.

Below this depth, you'll likely find a few crusts that were buried during the first few weeks of January. Due to limited observations, not much is known about the current reactivity of these layers.

The lower snowpack includes the more well-documented mid-December crust layer. Persistent slab avalanche activity from the Whistler area late last week suggests that heavy triggers like a large storm slab or cornice release may carry the risk of triggering this layer in isolated terrain - particularly in the north of the region where it has shown prolonged reactivity in snowpack tests.

Weather Forecast

Wednesday Night: 10-15cm of new snow / Moderate to strong southwest winds / Freezing level at 800m

Thursday: 3-5cm of new snow / Light southwest winds / Freezing level at 900m

Friday: 8-10cm of new snow / Light southwest winds / Freezing level at 1200m

Saturday: Light flurries / Light and variable winds / Freezing level at 1200m

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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