Avalanche Forecast

Issued: Mar 20th, 2014 9:17AM

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

Avalanche Canada bcorrigan, Avalanche Canada

Spring sun and rising freezing levels may increase the hazard above the forecast.  Large, mature cornices are now worth paying close attention to.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Synopsis: A northwesterly flow will bring cool and unsettled weather for the next few days .Tonight: Cloudy with clear periods, no precipitation in the forecast, freezing level around 300 metres, winds light, from the south west.Friday: Cloudy with flurries, no precipitation in the forecast, freezing level around 600 metres, light ridge top winds from the north.Saturday: Cloudy with snow, 5 to 10cm of precipitation, freezing level dropping to around 300 metres, ridge top winds should be light from the south east.Sunday: Sunny with cloudy periods, No precipitation in the forecast, freezing level around 900 metres, light ridge top winds from the east.

Avalanche Summary

Reports from Wednesday speak of large ( size 2.5 and 3) avalanches, initiating in the storm snow and stepping down to the persistent weak layers. There are also reports of loose wet avalanches on steep solar aspects. With rising freezing levels and spring sunshine, solar aspects may become quite active. Cornices have become quite large in some parts of the forecast region. They are definitely something to watch out for.

Snowpack Summary

50 to 75 cm of recent storm snow that arrived with strong winds has built more wind slabs at tree line and above, increasing the depth of the storm slab that now overlies the March persistent weak layer. In addition, the recent storm snow has fallen on a melt freeze and/or rain crusts that exist in most parts of the region below 1200 metres. This will most likely become reactive on solar aspects when the sun finally comes out.The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects and is widespread throughout the forecast region. This layer is now buried well over a metre in most parts of the region. A late January/early February crust/facet/surface hoar combo is still showing up in snowpack tests with moderate to hard shear tests. This layer will be with us for a long time, and a slide triggered on this layer would be very large and destructive. Recent warming temperatures will be good for bonding on this layer, but a sudden increase in load, or a large rainfall event could "wake up" this layer and result in very large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
Considerable amounts of new snow being redistributed onto lee slopes. This recent storm snow is sitting on a variety of older weak surfaces. Conservative terrain choices are critical right now. Rider triggered avalanches are definitely possible.
Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
The March and February weak layers have become reactive throughout the forecast region with recent new snow loading and strong winds.
Avoid runouts where triggering slopes from below is possible.>Avoid areas with overhead hazard.>Assess start zones carefully and use safe travel techniques.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 21st, 2014 2:00PM