Avalanche Forecast

Sea To Sky

Date issued

Dec 29, 2017 - 3:50 PM

Valid until

Dec 30, 2017 - 2:00 PM

Prepared by

ghelgeson

Natural avalanche activity is expected to tapper off early Saturday morning, but human triggered avalanches remain possible or even likely in wind loaded features, especially those that are steep and unsupported.

Regular season
Friday - December 29, 2017
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.

Saturday - December 30, 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

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.

Sunday - December 31, 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.

Avalanche Problem 1: Storm Slabs

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

Any natural activity induced by Friday night's storm should quickly taper off Saturday morning, but you need to remain vigilant in your travel practices, especially when it comes to avoiding convexities, terrain traps and wind loaded slopes.

Travel and Terrain Advice
  • Avoid wind loaded pockets at and above treeline, especially those near ridge crests and roll-overs.
  • Avoid large convexities and steep unsupported slopes.
  • The new snow could use a day to settle and stabilize before we start to tee up the bigger lines.

Avalanche Summary

On Thursday control work produced soft storm slabs to size 1.5 with crowns up to 45cm in depth. Natural avalanches to size 1.5 were also reported.

Snowpack Summary

Thursday's storm delivered 15 to 35 cm of new snow accompanied by moderate to strong winds out of the south/southwest. The new snow covers a medley of old surfaces which include stubborn old wind slabs and wind-scoured exposed crust in the alpine, and soft unconsolidated snow in sheltered areas at treeline and below.

20 to 60 cm below the surface you'll likely find a widespread melt-freeze crust that was buried on December 15th. This layer has not produced much in the way of avalanche activity, but could come to life with the additional load of new snowfall, especially in areas where loose facets exist above the crust.

Beneath the December 15th layer, the lower snowpack is generally strong and well settled.

Weather Forecast

One last blast of Pacific moisture is set to clash with the Arctic air mass over the province as a low pressure system moves towards the Lower Mainland late Friday. As was the case with Thursday's storm, alpine precipitation will fall as snow with only the North Shore Mountains at risk of seeing some liquid precipitation creeping up the slopes as warm air associated with the low just clips the Lower Mainland.

FRIDAY NIGHT: Freezing level at valley bottom, 10 to 30 cm of snow possible, moderate southwest wind.

SATURDAY: Skies clearing throughout the day, freezing level at valley bottom, light to moderate northwest wind, trace of snow possible.

SUNDAY: A few clouds, freezing level at valley bottom, light variable wind, no snow expected.

MONDAY: Scattered cloud cover, freezing level at valley bottom, light variable wind, no snow expected.

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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