Avalanche Forecast

Issued: Apr 1st, 2016 8:56AM

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

triley, Avalanche Canada

South Columbia.

Special Public Avalanche Warning extended for this region. Continued strong solar radiation and high freezing levels will keep the avalanche danger elevated.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

The ridge of high pressure that is responsible for the clear skies and very warm temperatures is slowly starting to move eastward. Freezing levels should drop a bit, but will remain above 2500 metres overnight and morning sun should quickly break down any crusts that develop. High cloud is expected to move into the interior ranges by Saturday afternoon. Moderate westerly winds on Saturday night combined with light precipitation may not drop freezing levels more than a few hundred metres, and may inhibit crust formation overnight. Sunday should be mostly sunny with light winds and freezing levels at 2500 metres. Freezing levels should begin to drop by Monday morning, when moderate southwest winds and precipitation move inland from the coast.

Avalanche Summary

On Thursday, strong solar radiation resulted in numerous loose wet avalanches up to size 3.0 on various aspects. Some wet slab activity was also reported from southerly aspects, and one persistent slab avalanche size 2.5 on a south aspect in the alpine that was 100-150 cm deep. I suspect that the strong solar on Friday resulted in another round of similar avalanche activity.

Snowpack Summary

New surface crusts have formed at all elevations on solar aspects, and on all but high alpine shaded aspects. Some areas have reported a new layer of surface hoar growing in high sheltered alpine locations above 2300 metres. Approximately 40-50 cm of settled storm snow sits on a melt-freeze crust buried on Mar. 22. The late February persistent weak layer is an aspect dependant mix of surface hoar, facets and/or a thick crust down around 60-110 cm below the snow surface. Commercial operators continue to see hard sudden planar results in snowpack tests, which suggests that wide fracture propagations are possible. Cornices continue to be described as large and fragile. Expect loose wet avalanches and natural cornice falls with strong solar radiation and significant warming this week. Forecast warming may trigger very large slab avalanches on one of the buried crusts or associated weak layers.

Problems

Cornices

Continued high freezing levels and very warm daytime temperatures are very likely to result in natural cornice falls. Large cornice falls may trigger buried weak layers resulting in very large avalanches.

Travel early before the heat of the day, and avoid big slopes in the afternoon.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Loose Wet

Forecast high freezing levels and very warm daytime temperatures may break down surface crusts early and result in loose wet avalanches from steep solar aspects. Wet slab avalanches are possible if loose snow propagates on a buried crust.

Be alert to conditions that change with elevation.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Continued warm and sunny weather may add enough heat to the snowpack to wake-up persistent weak layers buried in the snowpack. Rapid warming of the winter snowpack can result in deeply buried weak layers propagating very large avalanches.

Be careful with wind loaded pockets while approaching and climbing ice routes.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 2nd, 2016 2:00PM