Avalanche Forecast

Issued: Nov 27th, 2012 9:09AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

ccampbell, Avalanche Canada

Northwest Inland.

Avalanche danger is set to increase with stormy weather.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Wednesday: Snow with 10-15cm of accumulation, freezing levels in valley bottoms, and moderate southerly becoming extreme southeasterly winds. Thursday: Another 15-25cm of snow, freezing levels in valley bottoms, and strong to extreme southeasterly winds. Friday: Continued snowfall with another 5-10cm, freezing levels remaining in valley bottoms and extreme southeasterly winds.

Avalanche Summary

No new natural avalanches have been reported. Fresh wind slabs have been observed in exposed areas, but slope testing produced very few results.

Snowpack Summary

Snow depths vary throughout the region, with treeline depths in the southern part of the region (west of Smithers) ranging between a boney 70cm to a more typical 125cm, but highly variable with deep wind drifts and scoured slopes in exposed areas. A couple of notable weaknesses have been observed in the snowpack: first, a storm snow weakness (may also include small surface hoar) down 40-50cm. This layer should gain strength in the short term. Second, a facet/crust combo that formed in early November is now down 40-75cm. This layer has produced moderate "drops" results in recent snowpack tests. Because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, grassy areas, etc.). Check out the Skeena/Babine discussion forum for more information from this region.

Problems

Wind Slabs

Expect to find weak wind slabs below ridgecrests, behind terrain features, and in cross-loaded gullies. Natural avalanche activity is possible with heavy loading from snow and wind and human triggering is likely, especially on steep convex slopes.

Assess start zones carefully and use safe travel techniques.>Avoid freshly wind loaded features.>

Aspects: North, North East, East, South East, South.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Basal facet/crust weaknesses are often prone to remote triggering and step down avalanches, and typical trigger points include thin rocky areas. They may be difficult to trigger, but deep persistent slab avalanches are often very large.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Nov 28th, 2012 2:00PM