Avalanche Forecast

Sea To Sky

Date issued

Jan 1, 2018 - 6:18 PM

Valid until

Jan 2, 2018 - 2:00 PM

Prepared by

ghelgeson

Continued warm temperatures should allow the snowpack to further settle and stabilize, but small storm slabs in more extreme terrain may still be an issue. Watch for the odd loose wet avalanche on steep solar aspects in the afternoon too.

Regular season
Monday - January 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.

Tuesday - January 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.

Wednesday - January 3, 2018
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: Storm Slabs

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

Aided by wind, time and warmth, the storm snow is settling into a more cohesive slab. For the most part, this slab is bonding well to the underlying surface, but don't be too cavalier with your decision making, warming temps may change its behavior.

Travel and Terrain Advice
  • Caution with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Storm slabs could become more sensitive to human triggering as alpine temps approach +5 C Tuesday.

Avalanche Problem 2: Loose Wet

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

Natural loose wet avalanches remain possible Tuesday, especially on steep sun exposed slopes. With all the new snow in the last few days, loose wet avalanches could entrain considerable mass, especially in terrain traps like gulleys.

Travel and Terrain Advice
  • Minimize exposure to solar aspects overhead, loose avalanches could travel surprisingly far.
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
  • Avoid sun exposed slopes especially if the snow is moist or wet.

Avalanche Summary

On Monday several loose wet avalanches to size 1 were reported from southeast and south facing features between 1800 and 2100 m. On Sunday there was one report of a size 2.5 natural avalanche on a steep east facing feature in the alpine. There was also a small skier triggered avalanche on a southeast facing moraine feature at 1800 m. Loose dry avalanches to size 1 were reported from a variety of aspects.

Snowpack Summary

On Sunday a slight crust began to form on south and southwest facing aspects as warm temperatures and sun combined to moisten the snow surface. Cooler north and east facing features remain cold and dry.

Last Thursday and Friday two successive storms produced 50 to 70 cm of snow with wind mainly out of the south. The new snow rests on a variety of old surfaces including crust on solar aspects, old wind slabs, facets and isolated surface hoar below treeline, but avalanche activity on this interface continues to decrease as time and warm temperatures allow the old storm snow to settle and gain cohesion. Wind effect in the alpine has been widely reported but wind slab activity has been limited.

40 to 100 cm below the surface there is a widespread melt-freeze crust that was buried on December 15th. This layer has not produced much in the way of avalanche activity and is likely trending towards dormancy. Beneath the mid-December crust, the lower snowpack is generally strong and well settled.

Weather Forecast

This week will see a complete reversal in the weather pattern as warmer temperatures and dry conditions are expected to dominate. Warmer air aloft will prevail as an off shore upper ridge pushes inland and the flow aloft switches from cold northwesterly to mild southwesterly. This warm dry period is expected to persist through Friday.

TUESDAY: A few clouds in the morning, cloud cover increasing to broken by the afternoon, Freezing level around 2700 m, light southwest wind, no snow expected.

WEDNESDAY: Clear skies, freezing level around 2500 m, light southwest wind, no snow expected.

THURSDAY: Broken cloud cover, freezing level around 2000 m, light southwest 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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