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Avalanche Forecast

Archived

Feb 6th, 2020–Feb 7th, 2020

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 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, human triggered possible.

Regions

South Coast Inland.

Strong southwest wind will redistribute the recent snow and form wind slabs in lee terrain features at treeline and in the alpine. Rising freezing levels might weaken the upper snow pack at lower elevations. 

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

Thursday Night: Mix of clouds and clear skies, accumulation up to 5 cm in the south of the region, light to moderate northwest wind, alpine high - 5 C, freezing level 800 m. 

Friday: Flurries, accumulation 5 cm in most parts of the region and 10 cm in the south, strong southwest wind, alpine high -4 C, freezing level 1000 m in the north of the region and 1300 m in the south.

Saturday: Mix of sun and cloud, accumulation up to 5 cm in the north and 20-30 cm in the south of the region, light to moderate northwest wind, alpine high -4 C, freezing level 1000 m.

Sunday: Mix of sun and cloud, light to moderate northwest wind, alpine high -3 C, freezing level 1000 m.

Avalanche Summary

Numerous small (size 1) natural slab avalanches were observed below treeline which released within the recent storm snow and were very soft. Several small (size 1) and one large (size 2) loose dry avalanche were reported. 

The deep persistent slab avalanche activity observed during last weekend's storm in the northern portion of the region seems to have tapered off. Although the likelihood of triggering has reduced there is still concern for deep releases in that part of the region.

Snowpack Summary

The new snow sits on a variety of surfaces. Extreme southwest wind during the storm last weekend has scoured windward aspects, formed deep loaded pockets in alpine lees and contributed to rapid cornice growth. Below 1800 m, snow overlies a crust and tapers with elevation.

In the north part of the region (ie. Goldbridge/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 very large, deep persistent avalanches.

The south of the region, including the Coquihalla and Manning areas, currently have no concerns about deeply buried weak layers.

Terrain and Travel

  • Watch for avalanche hazard to increase throughout the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.

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.