Avalanche Forecast

Issued: Mar 21st, 2014 9:33AM

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

bcorrigan, Avalanche Canada

Northwest Inland.

The hazard may be higher than expected on solar aspects if the sun comes out and the temperature goes higher than forecast. Pay careful attention to cornice hazard.

Summary

Confidence

- Intensity of incoming weather systems is uncertain

Weather Forecast

Synopsis: A weak frontal system will pass through the area today and will be followed by a short-lived high pressure ridge.Tonight: Cloudy with clear periods, trace of precipitation in the forecast, freezing level at valley bottom, winds light, from the south west.Saturday: Cloudy with snow, 5 to 10cm of precipitation, freezing level around 300 metres, ridge top winds should be light from the south east.Sunday: Cloudy periods, trace of precipitation in the forecast, freezing level around 900 metres, light ridge top winds from the south east.Monday: Cloudy with snow flurries, 10 to 15cm precipitation, freezing level around 600 metres, winds light to moderate from the north.

Avalanche Summary

Some reports of natural avalanche activity in steep terrain, a few large heli-remotes and natural cornice failures producing large avalanches With continued loading and wind, rider triggering is definitely possible at this time.

Snowpack Summary

15 to 30cm of precipitation in the past week 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. A rain crust has formed at lower elevations, typically below 1200 metres. Solar aspects have been reported moist to ridgetops, and may have a crust with new snow on top of it. The solar aspects may become reactive when the sun comes out.The March weak layer is a combination of wind pressed snow, 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

Storm snow and winds have left us with wind slabs at tree line and above. Steep solar aspects may become active when the sun comes out on the recent storm snow. A cornice failure could produce a large destructive avalanche.

Avoid freshly wind loaded features.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Choose well supported terrain without convexities.>Be careful with wind loaded pockets while approaching and climbing ice routes.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

The persistent weak layers buried deep in the snowpack have recently become reactive with new snow loading. Conservative terrain choices are important now.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

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

Unlikely - Possible

Expected Size

4 - 7

Valid until: Mar 22nd, 2014 2:00PM