Avalanche Forecast

Sea To Sky

Date issued

Jan 11, 2018 - 4:27 PM

Valid until

Jan 12, 2018 - 2:00 PM

Prepared by

jlammers

If Friday night's storm arrives early, the avalanche danger may be higher than posted.

Regular season
Thursday - January 11, 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 - January 12, 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.

Saturday - January 13, 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?

New snow and wind on Friday afternoon is expected to promote new storm slab development and increase the avalanche danger at the end of the day. If the new snow arrives early, the avalanche danger may be higher than posted.

Travel and Terrain Advice
  • Be alert to conditions that change with elevation and time of day.
  • Be cautious in lee features above treeline, old wind slabs rest on a buried crust.
  • Watch for fresh storm slabs building throughout the day.

Avalanche Summary

On Wednesday the upper snowpack was largely unaffected by explosives control work, but it did produce a few storm slab avalanches to size 1. Ski cutting in the region also produced similar avalanche activity in isolated terrain.

Snowpack Summary

10 to 15 cm of light density snow from Monday night and Tuesday now rests on 20 to 30 cm of slightly heavier snow that fell over the weekend. This snow was redistributed by moderate to strong southeast through southwest winds on Sunday. All of this snow is above the the January 6th crust which is present to at least 2100 m, maybe higher. This crust is reportedly breakable below 2100 m. Below the crust there is about 20 cm of settled moist snow.

Up to 100 cm below the surface there is a widespread melt-freeze crust that was buried on December 15th, but this layer has not produced any recent avalanche activity and is trending towards dormancy.

Beneath the mid-December crust, the lower snowpack is generally strong and well settled.

Weather Forecast

Friday: About 5cm of the new snow with an additional 10-15cm overnight / Moderate southwest winds / Freezing level at 600m

Saturday: Mix of sun and cloud / Light southwest winds / Freezing level at 1400m

Sunday: Mostly clear skies / Light southwest winds / Freezing level at 2300m

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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