Avalanche Forecast

Issued: Mar 18th, 2014 9:18AM

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 - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Synopsis: A low pressure system in the north Pacific continues to feed moisture onto the BC coast.Tonight: Cloudy with flurries, possible 10 to 20cm of precipitation,, freezing level around 300 metres winds from the south light occasionally gusting to strong.Wednesday: Cloudy with flurries, 5 to 10cm of precipitation expected, freezing level around 500 metres, ridge top winds light from the west, gusting to moderate.Thursday: Cloudy with sunny periods and possible flurries, trace amounts of precipitation, freezing level around 600 metres, winds light, from the west, occasionally gusting to moderate.Friday: Cloudy with flurries, 5 to 10cm of precipitation. Freezing level around 600 metres, light ridge top winds, occasionally gusting to moderate.

Avalanche Summary

Reports of large natural avalanche cycle during and after Mondays precipitation and wind event. Avalanches up to size 3, 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

10 to 25cm of recent precipitation and strong winds continue to build wind slabs in lee terrain and increase the depth of the storm slab that 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 exist 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.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

Wind slabs continue to build on lee slopes and storm snow is sitting on a variety of older weak surfaces. Steep south aspects have sun crusts. Conservative terrain choices are critical right now. Rider triggered avalanches are definitely possible.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

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.

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

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.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 19th, 2014 2:00PM