Avalanche Forecast

Issued: Mar 16th, 2014 9:46AM

The alpine rating is high, the treeline rating is high, 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 - Due to the number and quality of field observations

Weather Forecast

Synopsis: A low pressure system in the Gulf of Alaska will feed varying amounts of moisture onto the coast for the next 4 or 5 days.Tonight: Clearing as precipitation tapers off, freezing level at valley bottom, winds from the north west up to 50 km/hr.Monday: Cloudy, 5 cm of precipitation in the forecast, freezing level around 600 metres, winds from the south west, 50 Km/hr.Tuesday: Cloudy with flurries, possible 5 to 10 cm of precipitation,, freezing level around 800 metres winds from the south west light occasionally gusting to moderate.Wednesday: Sunny with cloudy periods and isolated flurries, not much precipitation expected, freezing level around 700 metres, winds light from the west, gusting moderate to strong.

Avalanche Summary

Observations during the storm have been limited but we have received reports of wind slab activity and explosive triggered slabs releasing on the early-March layer. Widespread natural activity is expected for Saturday night and Sunday.

Snowpack Summary

Storm slabs continue to build. S-SW winds are building wind slabs in lee features. A widespread crust is expected below the storm snow at lower elevations.Before this weekends storm, the early March persistent weak layer was down up to 1m in the north of the region. The south of the region had less snowfall and the slab was down roughly 60cm. This weak layer consists of any of the following: hard wind slabs or wind-scoured slopes in exposed terrain, a thick layer of faceted snow on sheltered/shady slopes, isolated surface hoar on sheltered/shady slopes, and sun crust on steep solar aspects. The early-February weak layer of surface hoar or a crust/facet combo is typically buried over 1.5m deep. This layer continues to react in snowpack tests, primarily on sheltered north aspects around tree line. The weight of the new snow and rain has the potential to reactivate this layer resulting in large, destructive avalanches. Basal facets and/or depth hoar remain an isolated concern in shallow snowpack areas in the northern part of the region.

Problems

Storm Slabs

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

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

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.>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 17th, 2014 2:00PM