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Avalanche Forecast

Archived

Feb 1st, 2020–Feb 2nd, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

If you choose to tiptoe out into the mountains this weekend, stick to conservative, low consequence terrain and avoid overhead hazard. 

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

Saturday night: Partly cloudy. Moderate southwest wind. Freezing level valley bottom.

Sunday: Mix of sun and cloud with isolated flurries. Moderate southwest wind. Alpine high -8 C. Freezing level valley bottom.

Monday: Mix of sun and cloud. Light northwest wind. Alpine high -8 C. Freezing level valley bottom.

Tuesday: Mostly cloudy with flurries. Moderate west wind. Alpine high -6 C. Freezing level valley bottom.

Avalanche Summary

A natural storm slab cycle up to size 2.5 was observed Friday night along the Duffey Lake road corridor. Avalanche results from explosive control work is suspected to have run on the deep persistent crust.

Reports of very large (size 3) deep persistent avalanches have been steadily coming in over the past week from the north half of the region. The most recent events occurred on Monday near Goldbridge, Whitecap and Duffey Lake. While most of these events have been naturals on north to east aspects in the alpine, some have been remotely triggered by skiers.

Snowpack Summary

Recent snow continues to be loaded into lee features in the alpine by moderate southwest wind. Above 1800 m, storm totals for the north of the region are in the range of 30-50 cm, while the Coquihalla received around 100 cm and the Manning Park area received around 35 cm. Below 1800 m, snow overlies a crust and tapers with elevation.

In the north half of the region (ie. Goldbridge/Whitecap/Duffey/Hurley), a few deep instabilities exist in the snowpack, including a weak basal facet crust complex. This has been the failure plane in ongoing reports of deep persistent avalanches. The significant new loads from snowfall and rain will stress the deep basal weakness.

The south of the region, including the Coquihalla and Manning areas, currently have no concerns about deep instabilities.

Terrain and Travel

  • Make conservative terrain choices and avoid overhead hazard.
  • Be alert to conditions that change with elevation.
  • Avoid freshly wind loaded terrain features.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Brief periods of sun could quickly initiate natural avalanche activity.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.