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Avalanche Forecast

Archived

Feb 4th, 2020–Feb 5th, 2020

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

Posted avalanche danger ratings are for the north of the region where a deep persistent avalanche problem continues to be a concern. Avalanche danger in the south of the region (Coquihalla and Manning areas) is MODERATE in the alpine.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Tuesday Night: Flurries, accumulation 5-10 cm. Moderate to strong southwest and west wind. Alpine high -8 C.

Wednesday: Flurries, accumulation 5 cm. Strong west wind. Alpine high -4 C. Freezing level 1200 m.

Thursday: Snow, accumulation 5-10 cm in the north of the region and 15-30 cm in the south. Moderate to strong west wind. Alpine high -2 C. Freezing level 1000 m.

Friday: Flurries, accumulation 5 cm. moderate west wind. Alpine high -4 C. Freezing level 1000 m.

Avalanche Summary

There have been no recent reports of avalanche activity. 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 is still concern for deep releases in that part of the region.

Snowpack Summary

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

  • Be especially cautious as you transition into wind affected terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.