Avalanche Forecast

Sea To Sky

Date issued

Dec 14, 2017 - 4:10 PM

Valid until

Dec 15, 2017 - 2:00 PM

Prepared by

jmcbride

With snow expected to begin on Friday and continue into the weekend, watch for touchy wind slabs building in alpine, lee areas.

Regular season
Friday - December 15, 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.

Saturday - December 16, 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.

Sunday - December 17, 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.

Avalanche Problem 1: Wind Slabs

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

The bond between the new snow and the old surface will be the big question once the storm snow starts to accumulate and be redistributed by winds.

Travel and Terrain Advice
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Avalanche Summary

There have been no reports of avalanche activity since the weekend when a small, natural, wind slab avalanche was observed in the alpine on a wind-loaded, north-facing, ridge top feature on Saturday in the Metal Dome area.

Snowpack Summary

A melt-freeze crust exists on the surface on all aspects. On north aspects this surface crust is thin with dry, sugary snow crystals (facets) below. Beneath the surface, the upper snowpack is well settled and overlies a thin layer of facets on the late-November rain crust. The most recent snowpack tests from last week have found hard, sudden compression test results on the facets just above the crust, which is now buried between approximately  60 cm at treeline elevations. Beneath this crust the lower snowpack is well settled and consists of several crusts that formed in the early season.

Weather Forecast

FRIDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind light to moderate from the northwest. Temperature -1. Freezing level 800 m.

SATURDAY: Mix of sun and cloud, flurries. Accumulation 5 cm. Ridge wind light from the west. Temperature -3. Freezing level 800 m.

SUNDAY: Cloudy, flurries. Accumulation 5-15 cm. Ridge wind moderate from the southwest. Temperature -2. Freezing level 800 m.

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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