Avalanche Forecast

Issued: Mar 20th, 2014 9:20AM

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.

bcorrigan, Avalanche Canada

Northwest Inland.

Hazard could go higher than forecast if temperatures and solar radiation exceed expectations. Cornices are becoming mature and could fail with warm temperatures and increasing loads.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A northwesterly flow will bring cool and unsettled weather for the next few days .Tonight: Cloudy, trace to 5 cm of precipitation, freezing level at valley bottom, winds light from the south east.Friday: Cloudy, no precipitation in the forecast, freezing level at valley bottom, light south east ridge top winds.Saturday: Cloudy with snow, 5 to 10cm of precipitation, freezing level at valley bottom, ridge top winds, light to moderate from the south east.Sunday: Sunny with cloudy periods, No precipitation in the forecast, freezing level around 600 metres, light ridge top winds from the north.

Avalanche Summary

Wednesdays' reports speak of a number of large ( size 3 ) avalanches in the region, most were natural avalanches, with 1 skier remote to the north and a cornice failure triggering a size 3 in the western part of the forecast area.With continued loading and wind, rider triggering is definitely possible at this time.

Snowpack Summary

10 to 20cm of recent precipitation in some parts of the forecast region. That, combined with strong winds continues to build wind slabs in lee terrain and increase the depth of the storm slab that overlies the persistent weak layers. At lower elevations the storm snow has fallen on a melt freeze and/or rain crusts that exists in most parts of the region below 1200 metres. This could 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 some 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

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.

Choose well supported terrain without convexities.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

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

Be aware of thin areas that may propogate to deeper instabilites.>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 - Likely

Expected Size

2 - 4

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

Unlikely - Possible

Expected Size

4 - 7

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