Avalanche Forecast

South Coast Inland

Date issued

Mar 16, 2018 - 4:47 PM

Valid until

Mar 17, 2018 - 2:00 PM

Prepared by

cgarritty

Observations of reactive surface hoar have renewed concern for slab avalanche danger in the north of the region. Avalanche danger is generally LOW in the south of the region, requiring normal cautions.

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

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 - 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

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.

Sunday - March 18, 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.

Avalanche Problem 1: Storm Slabs

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

Recent reports are showing continued slab reactivity on shaded aspects where recent snowfall overlies surface hoar. South aspects become an additional daily concern as sun and warming set up loose wet avalanche conditions.

Travel and Terrain Advice
  • Extra caution needed around cornices with current conditions.
  • Use extra caution on solar slopes or if the snow is moist or wet.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Avalanche Summary

Reports from Thursday included one observation small storm slab releasing with a ski cut on the steep flank of a couloir in the north of the region. Several other recent natural storm slab releases were observed in the same area, ranging from size 1-2 with crown fracture depths of 10-30 cm. North aspects were the most active.

Monday's reports showed one size 1.5 wind slab that released with skier traffic on a steeper north aspect (near ridgecrest) in the alpine near Birkenhead Lake. Several solar triggered loose wet releases were reported, averaging size 1.5-2 but reaching size 3 in isolated areas.

Snowpack Summary

5-10 cm of new snow accumulated on Wednesday. In most areas, the new snow has buried a breakable crust formed after days of warm temperatures and sunshine. On higher elevation north aspects in the north of the region, is overlies a mix of about 20 cm of either low density or wind-redistributed storm snow from last week. This older storm snow sits on a sun crust on steep south-facing slopes, cold dry snow and possibly small surface hoar on shady aspects. Recent reports have shown prolonged slab reactivity in areas in the north of the region where this surface hoar exists.

In the north of the region a weak layer buried in mid-February is about 40-50 cm below the surface and has been reactive in some snowpack tests. The layer is composed of sugary facets, a sun crust on solar aspects, and surface hoar that is present at and below treeline. The snowpack is well settled in the south of the region around the Coquihalla and in Manning Park.

Variable winds in the past month have created cornices on many alpine ridgelines. They become touchier as daily temperatures rise and with the strong late winter sun on clear days.

Weather Forecast

Saturday: A mix of sun and cloud. Light northeast winds. Freezing level to 1400 metres with alpine high temperatures of -4, slightly warmer in the south of the region.

Sunday: Cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1300 metres with alpine temperatures around -5, slightly warmer in the south of the region.

Monday: A mix of sun and cloud. Light southwest winds. Freezing level to 1400 metres with alpine temperatures around -4, slightly warmer in the south of the region.

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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