Avalanche Forecast

Issued: Mar 17th, 2014 9:56AM

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

bcorrigan, Avalanche Canada

Sea To Sky.

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 at valley bottom, 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 5 to 10cm 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

A few reports from yesterday of skier accidental and skier controlled as well as some explosive controlled avalanches, in the size 1 to 2 range in the storm snow, mostly wind loaded features above tree line. As well there are reports of sluffing in steep solar affected terrain.

Snowpack Summary

Up to 35 cm of recent storm snow is sitting on a variety of layers. A well developed sun crust has formed on solar aspects and prior to this storm, surface hoar formed on shady, sheltered slopes. At lower elevations, a melt-freeze (or rain) crust can be expected in most areas. Moderate to strong SW winds have formed wind slabs on lee slopesBelow the storm snow, the upper snowpack is generally well settled from the recently warm weather. Two persistent weak layers remain a concern but these problems are becoming more isolated. Before the storm, the early-March crust/facet layer was down roughly 1m and the early Feb layer is down 1.5m or more. These layers are now deep enough that human-triggering is unlikely, but smaller avalanches or cornices failures have the potential to step down to these layers. Freezing levels have been cycling between valley bottom and 1500-2000m, and low elevation terrain saw significant rain last weekend. The snowpack at lower elevations has been generally stable but wet snow or rain may destabilize the upper layers of the snowpack.

Problems

Storm Slabs

Strong winds have built wind slabs on lee slopes, watch out for wind loaded pockets. Expect sluffing in steep terrain, especially on steep solar aspects. Cornices are becoming large and mature give them a wide berth.

Avoid areas with overhead hazard.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid steep slopes below cornices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

Two deep persistent weak layers continue to be a concern within the snowpack. These have been quiet recently but may "wake up" with the weight of the new storm snow. Smaller avalanches may step down and trigger one of these deeper layers.

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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

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