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Avalanche Forecast

Mar 30th, 2016–Mar 31st, 2016
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Columbia.

Special Public Avalanche Warning for this region. Forecast very warm temperatures, high freezing levels, and strong solar radiation will increase the avalanche danger to HIGH in the alpine during the hottest part of the day.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A well-developed ridge of high pressure will continue to provide clear skies, light winds, and very warm temperatures for Thursday and Friday. Freezing levels may climb as high as 3000 metres, and there may not be a freeze on Friday morning in some areas. A weak trough will move inland from the coast on Saturday, bringing moderate southwest winds and increasing cloud cover. Some light precipitation may make it into the Interior ranges, however it may be mostly rain as the freezing level should remain at about 2500 metres on Saturday.

Avalanche Summary

On Tuesday numerous solar triggered loose wet avalanches were reported up to size 2.5. On Monday some recent storm slab avalanches were reported releasing from skier triggering up to size 1.0 on north aspects in the alpine. Some natural cornice activity was also reported up to size 2.5 from northeast and easterly aspects in the alpine. Forecast very warm temperatures and high freezing levels are expected to increase natural cornice activity, and may trigger the buried persistent weak layers.

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.

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

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 3 - 6