Avalanche Forecast

Archived

Dec 24th, 2011–Dec 25th, 2011

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary.

Click on the 'Forecaster's Blog' link below for more discussion on how to travel safely under the current conditions.

Confidence

Fair - Due to variable weather conditionsfor the entire period

Weather Forecast

Sunday: Generally light snowfall with a pulse of moderate snowfall expected in the afternoon. The freezing level will rise to 800m by afternoon. Strong south-westerly winds at ridge top.Monday/Tuesday: Further light precipitation with moderate-strong south-westerly winds. The freezing level should slowly rise in the early part of the week.

Avalanche Summary

No new avalanches have been reported.

Snowpack Summary

Recently developed surface hoar and near-surface facets are getting gently buried by light snowfall, potentially creating a weak interface which could become reactive with enough new load from snow and/or wind-transport.Other buried surface hoar layers exist in the upper 15-25cm (with sudden test results on these layers in some locations). Soft and hard wind-slabs can be found on certain slopes in the alpine and around treeline. Generally light snowfall amounts are forecast for the region over the next few days. Without the certainty of heavy or rapid loading, it's hard to know when the weight of new snow building over buried weaknesses might reach a tipping point. Areas with locally heavier snowfall should reach this point sooner. Facets at the base of the snowpack could create a deep persistent slab problem that deserves attention in shallow snowpack areas on planar rocky slopes.

Problems

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.