Avalanche Forecast

Issued: Apr 7th, 2012 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Loose Wet, Persistent Slabs and Cornices.

pmarshall, Avalanche Canada

Sea To Sky.

Avalanche danger will rise during the day with intense spring sunshine and warming temperatures. Plan to be off big sun-exposed slopes early before the snow becomes moist or wet.

Summary

Confidence

Good

Weather Forecast

Sunday: Sunny during the day with increasing cloud in the afternoon/evening. Winds are light from the south-southeast. The freezing level should be around 1800-2000. Monday: Mainly cloudy with some sunny breaks and a chance of light precipitation. Winds are light to moderate from the southeast. The freezing level hovers around 1800-2000m.Tuesday: Mainly cloudy with light precipitation ~ 5mm. The freezing level stays fairly high at 2000-2200m.

Avalanche Summary

New observations include several loose-wet avalanches up to Size 2 from steep solar aspects. Reports from earlier in the week include natural activity up to Size 3 in response to direct sun-exposure. One natural Size 3, 160cm thick slab avalanche on a steep NE facing alpine glacier was suspected to have failed on the late-March interface. A settlement was felt 1 Km away during this avalanche, which suggests a high propensity to propagate fractures.

Snowpack Summary

Solar aspects and lower elevations have gone through a melt-freeze cycle for the past few days. Shady north aspects have had some recent surface hoar growth and surface faceting. This sits on around 100 cm of well settled storm snow from last week. A predominately crusty weak interface from late March, now down 50-150cm, remains a potential failure layer for large slab avalanches, especially with heavy triggers such as cornice falls and step-down avalanches. Not only will daytime warming and sun-exposure cause surface snow to lose cohesion and cornices to weaken, they will also increase settlement rates and decrease slab stability.

Problems

Loose Wet

Very likely on steeper sun-exposed slopes in the afternoon. A heavy wet slide could have serious consequences if you are exposed to terrain traps.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Becoming less likely, but the potential exists for remote triggering, step down avalanches, and wide propagations, especially during periods of intense solar radiation and daytime warming.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Cornices

Large and weak cornices could easily start popping off with sun-exposure. Not only are they a hazard in themselves, but can also act as a heavy trigger for very large avalanches on the slope below.

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 8th, 2012 9:00AM