Avalanche Forecast

Issued: Feb 29th, 2012 9:17AM

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

Avalanche Canada pgoddard, Avalanche Canada

Summary

Confidence

Fair - Due to variable weather conditions for the entire period

Weather Forecast

Thursday: Flurries, accumulating to about 5cm. Light, north-westerly winds. Freezing level valley floor. Friday: Moderate snowfall starting in the afternoon or evening. Highest amounts (around 15cm) in the north and west of the region. Freezing level gradually starting to rise. Winds shifting to westerly and increasing.Saturday: Snow continuing, with variable amounts from place to place (perhaps 10cm on average). Freezing level rising to around 1400m. Moderate westerly winds, except in the far south, where winds are forecast to be strong south-westerly. In general, snowfall amounts and winds are forecast to be highly variable across the region.

Avalanche Summary

Avalanche activity has begun to slow, with avalanche size and frequency decreasing. However, a number of avalanches are still being triggered remotely (from several hundred metres away) and accidentally by skiers and machinery. These avalanches are failing on upper snowpack persistent and storm snow weaknesses, on almost all aspects and elevations. Human-triggering of destructive avalanches remains a distinct possibility, while in-your-face clues of instability are diminishing.

Snowpack Summary

Tricky snowpack conditions continue, which will require a high degree of training and judgement to evaluate safely. 60-140cm of recent storm snow is slowly settling/stiffening above the Feb 16. surface hoar layer and the early Feb interface. A storm snow weakness down about half a metre is touchy in some areas. The early Feb interface consists mainly of surface hoar (widespread) or a melt-freeze crust (on solar aspects). It is challenging to pin down exactly where you are most likely to trigger these persistent weaknesses. Some operators are most concerned around treeline, others on solar aspects, and others on almost any slope, including low-angled terrain. Remote, natural and human-triggered avalanches have been observed all over. You will need to investigate the snowpack in your local area to find and test these layers. Triggering wind slabs is becoming less likely, but they exist on many slopes and bury the upper snowpack weaknesses deeply in places. Large cornices loom as potential triggers for deep avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
A storm snow weakness down about half a metre remains touchy, especially on steep or convex terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Several weaknesses exist in the upper metre or so of the snowpack. Large, destructive avalanches could be triggered by the weight of a person, even from a distance.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 7

Wind Slabs

An icon showing Wind Slabs
Wind slabs lurk on many slopes. Persistent weak layers are buried beneath these slabs, meaning they could step down to create very large avalanches. Large cornices also threaten many slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Mar 1st, 2012 8:00AM