Avalanche Forecast

Sea To Sky

Date issued

Dec 2, 2017 - 3:55 PM

Valid until

Dec 3, 2017 - 2:00 PM

Prepared by

mgrist

The lure of powder slopes and sunny skies will be strong on Sunday. Take a cautious approach towards more aggressive terrain - especially steep, wind-affected terrain.

Regular season
Saturday - December 2, 2017
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.

Sunday - December 3, 2017
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.

Monday - December 4, 2017
Alpine

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.

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?

Wind slabs have been building over a crust layer. This layer may slide easily, particularly on steep convex terrain or where the wind has blown it into more cohesive slabs.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Avoid steep lee and cross-loaded features
  • Be alert to changing snow conditions, especially where the snow firms up or sounds hollow.

Avalanche Summary

On Saturday, control work with explosives gave mostly Size 1 soft slabs.

Over the past three days, ski cutting has consistently produced soft slab avalanches on lee and cross-loaded features, running to size 1.5 in the storm snow at treeline and alpine elevations.

On Friday, most slabs triggered were approximately 25cm thick, running on a density change within the recent storm snow.

Snowpack Summary

Approximately 40-60 cm new snow now sits on top of a rain crust (or multiple crusts) that formed during the wet weather at the end of November. Strong (southerly) winds have blown snow around in exposed areas creating drifts and scoured areas.

The main areas of concern are lee (northerly) and cross-loaded features in the alpine and treeline elevation bands.

Snowpack depths are typically around 150 cm in sheltered treeline locations, although deeper (and shallower) spots certainly exist on account of the strong winds.

Weather Forecast

We'll see a clearing trend on Sunday and fine weather during the week.

Sunday: Clearing in the morning and then dry with some sunny breaks. Light northwesterly winds. Freezing levels 800m.

Monday: Sunny with cloudy periods. Freezing levels around 600 m. Light northwesterly winds.

Tuesday: Mainly sunny and becoming warm up high. Freezing levels rising to 2000 m. Light northerly winds.

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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