Avalanche Forecast

Sea To Sky

Date issued

Mar 15, 2018 - 4:52 PM

Valid until

Mar 16, 2018 - 2:00 PM

Prepared by

cgarritty

Lingering wind slabs remain a concern on high elevation north aspects. Exercise increasing caution around solar aspects and lower elevations as loose wet avalanche conditions develop over the day.

Regular season
Friday - March 16, 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.

Saturday - March 17, 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.

Sunday - March 18, 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: Wind Slabs

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

Recent snowfalls formed wind slabs that still linger in north facing terrain. South aspects aren't exempt - they become an increasing concern over the day as sun and warming set up loose wet avalanche conditions.

Travel and Terrain Advice
  • Give cornices a wide berth while on or below ridges. Cornice falls may trigger large avalanches.
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
  • Watch for wind-loaded pockets around ridgecrests and in the lee of exposed terrain features.

Avalanche Summary

Reports from Monday included observations of three natural size 2.5 loose wet avalanches that released from steep, rocky, south-facing slopes in the afternoon in the Whistler area.

On Sunday there was a report of a skier triggered size 2 storm slab avalanche on a west aspect at 2400m. On Saturday there were several size 2.5 natural persistent slab avalanches reported. These were suspected to have run in the previous 24hours and were observed on northwest to east aspects between 1900 and 2000m. Additionally there have been several observations of skier triggered storm and wind slab avalanche size 1-2 mostly on northerly aspects between 1800 and 2000m.

Snowpack Summary

About 10 cm of new snow accumulated over Tuesday night and Wednesday. In most areas the new snow buried a surface of variable crust and moist snow, the product of days of warm temperatures and sunshine. On high elevation north aspects, the new snow may overlie dry, wind redistributed snow from last week's storms.

Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust found roughly 50-100 cm below the surface. A week ago this layer was producing whumpfing, sudden results in snowpack tests, and even some remotely triggered avalanches. Much of this activity was attributed to buried surface hoar on north aspects at upper treeline elevations. This buried weak layer is a limited but lingering concern in a snowpack that is otherwise well settled and strong beneath this interface.

Variable winds in the past month have built up cornices on many ridgelines. They will become touchier as daily temperatures rise and when they are subject to the strong late-winter sun on clear days.

Weather Forecast

Friday: Mainly sunny. Light variable winds. Freezing level to 1500 metres with alpine high temperatures of -3.

Saturday: A mix of sun and cloud with increasing cloud and light flurries beginning in the afternoon. Light north winds. Freezing level to 1500 metres with alpine high temperatures of -3.

Sunday: Cloudy with isolated flurries and a trace of new snow. Light northwest winds. Freezing level to 1400 metres with alpine high temperatures around -4.

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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