Date issued

Feb 7, 2018 - 8:00 AM

Valid until

Feb 8, 2018 - 8:00 AM

Prepared by

percy woods

The Pacific storm is bringing heavy snowfall between this morning and Thursday evening.  Limit exposure to overhead avalanche hazard. Make conservative terrain choices!

Regular season
Tuesday - February 6, 2018
Alpine

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.

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.

Wednesday - February 7, 2018
Alpine

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.

Treeline

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.

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.

Thursday - February 8, 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

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: Storm Slabs

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

40cm new snow and mod winds, our storm slab is not getting time to heal. A layer of large stellars was found down 25cm Monday, which could have been the culprit layer in regards to the size 2 skier accidental slide reported Monday on McGill.

Travel and Terrain Advice
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Avalanche Problem 2: Persistent Slabs

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

The Jan 16th, 4th and Dec 15th surface hoar layers have been quiet recently but may reawaken given a large trigger such as a storm slab avalanche or cornice fall.

Travel and Terrain Advice
  • Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Avalanche Problem 3: Loose Dry

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

Rapid snowfall on top of the 20cm+ already received this week will prime the surface for sluffing. Both natural and skier triggered sluffing can be expected today.

Travel and Terrain Advice
  • The new snow will require several days to settle and stabilize.
  • Use caution above cliffs where small avalanches may have severe consequences.

Avalanche Summary

Several naturals in the HWY corridor Monday up to size 3. Only three new slides observed in the corridor Tuesday. On McGill Shoulder Monday there was a skier accidental size 2, 30-50cm deep, 50m wide and ran for 300m in length. Significant sluffing was also observed in the Bostock drainage.

Snowpack Summary

A winter storm is potentially bring us 40cm+ snow by Thursday evening. Previous strong S'ly winds created wind slabs in the alpine and exposed areas at TL. These slabs are now buried under fresh storm slab formations. Recent observations showed failures at these interfaces, with potential to step down to our plethora of persistent weak layers.

Weather Forecast

A winter storm is upon us and is forecast to bring us 40cm+ of snow by the end of the day Thursday. The main pulse should occur Wednesday night into Thursday morning. Moderate to strong SW winds and rising freezing level to 1500m will prime the surface layers with wind and storm slab formation.

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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