Avalanche Forecast

Sea To Sky

Date issued

Jan 3, 2018 - 4:51 PM

Valid until

Jan 4, 2018 - 2:00 PM

Prepared by

ghelgeson

Low avalanche danger doesn't necessarily equate to no avalanche danger. The odd small storm slab may still be human triggerable in more extreme terrain. The picture should start to change on Saturday as storm snow returns to the Sea to Sky.

Regular season
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.

Thursday - January 4, 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.

Friday - January 5, 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.

Avalanche Problem 1: Storm Slabs

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

Aided by wind, time and warmth, the storm snow has settled into a stubborn old slab. For the most part, this slab is bonding well to the underlying surface but there may still be an issue in more extreme terrain.

Travel and Terrain Advice
  • Caution with wind slabs, especially in steep, unsupported and/or convex terrain features.

Avalanche Summary

On Tuesday snow balling and pin wheeling was reported from north facing aspects. On Monday several loose wet avalanches to size 1 were reported from southeast and south facing features between 1800 and 2100 m.

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. By Tuesday the upper 5 cm of the snowpack had started to become moist, even on upper elevation northeast facing features.

Last Thursday and Friday two successive storms produced 50 to 70 cm of snow with wind mainly out of the south. Time and warm temperatures have allowed this snow to settle and bond well with the underlying surface. The exception may be below treeline where there may be isolated pockets of buried surface hoar. Wind effect in the alpine has been extensive but reported wind slab avalanche activity has ceased.

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

The weather pattern is changing, albeit slowly.  As the ridge shifts east, a trough pattern on the west coast begins to bring cloud and precipitation beginning Thursday.

THURSDAY: Overcast, light temperature inversion with the freezing level around 2500 m, light southerly wind, trace of precipitation possible in the late afternoon.

FRIDAY: Overcast, freezing level around 2000 m, light to moderate south/southwest wind, 3 to 6 mm of precipitation expected.

SATURDAY: Overcast, freezing level around 1100 m, light to moderate southwest wind, 3 to 6 mm of precipitation 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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