Avalanche Forecast

Issued: Mar 19th, 2014 9:29AM

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

bcorrigan, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Saturday

Weather Forecast

Synopsis: A low pressure system over northwest BC will track south eastward through BC and into Alberta.Tonight: Cloudy with flurries, freezing level around 200 metres, winds from the south light occasionally moderate.Thursday: Cloudy with sunny periods and possible flurries, trace of precipitation, freezing level around 700 metres, winds light, from the west.Friday: Cloudy with flurries, Freezing level around 600 metres, light ridge top winds, occasionally gusting to moderate.Saturday: Cloudy with snow, 15 to 20cm of precipitation, freezing level around 800 metres, ridge top winds, light from the south east.

Avalanche Summary

Not many reports of avalanche activity from Tuesday, which is more likely because of poor weather and visibility, rather than lack of avalanche activity. Large natural avalanche cycle up to size 3's reported on Monday, initiating in the storm slab and running on the early March and Feb. 10th persistent weak layers. With continued loading and wind, rider triggering is definitely possible at this time.

Snowpack Summary

35 to 50 cm of 24 hr. precipitation combined with moderate to strong winds continues to build wind slabs at tree line and above, increasing the depth of the storm slab that now overlies the March persistent weak layer. This persistent weak layer is now buried well over a metre in most parts of the region. 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.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

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 all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

The March and February weak layers have become reactive throughout the forecast region with recent new snow loading and strong winds.

Assess start zones carefully and use safe travel techniques.>Avoid areas with overhead hazard.>Avoid runouts where triggering slopes from below is possible.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 20th, 2014 2:00PM