Avalanche Forecast

Issued: Mar 17th, 2014 9:37AM

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

bcorrigan, Avalanche Canada

South Coast.

Summary

Confidence

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

Weather Forecast

Synopsis: Low pressure systems in the north Pacific continues to feed moisture into BC.Tonight: Cloudy with flurries, no serious precipitation expected, freezing level around 400 metres, winds from the west occasionally gusting to moderate.Tuesday: Cloudy with snow, trace to possible 5cm of precipitation, freezing level climbs to 1200 metres, winds from the south west light, gusting to moderate.Wednesday: Cloudy with flurries, possibility of 10 to 15cm of precipitation, freezing level around 900 metres, ridge top winds moderate from the west.Thursday: Cloudy with sunny periods and isolated flurries, 5 to 10cm of precipitation, freezing level around 1000 metres, winds light occasionally gusting to moderate from the west.

Avalanche Summary

The Coquihalla reported a large natural avalanche cycle yesterday with avalanches up to size 3. A size 2 was rider triggered in the needle peak area with a serious involvement. A rider triggered (large) size 1 was reported in the Duffey lake area from yesterday

Snowpack Summary

Between 50 and 70 cm of recent storm snowstorm snow at upper elevations is sitting on a a variety of weak layers. Strong SW storm winds have formed wind slabs on lee slopes. The two persistent weak layers that remain a concern are:The March weak layer. 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 generally widespread throughout the forecast region.A late January/early February crust/facet/surface hoar combo that is still showing up in snowpack tests with 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.With recent storm snow loading, the March layer is now down around 60 to 70cm and the early February layer should be roughly 1.8m. These persistent weak layers may still pose a threat for some time in the forecast region.

Problems

Storm Slabs

The recent storm has left us with wind slabs at tree line and above. Cornices are getting large and mature. Solar aspects may become active when the sun comes out on the recent storm snow

Be cautious as you transition into wind affected terrain.>Pay attention to overhead hazards like cornices.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

The deep persistent weak layers may be touchy after all the new storm snow, careful terrain evaluation is called for now.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 18th, 2014 2:00PM