Avalanche Forecast

Issued: Mar 31st, 2016 4:00PM

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

jfloyer, Avalanche Canada

South Columbia.

Special Public Avalanche Warning for this region. Continued very warm temperatures with little overnight freeze coupled with strong solar radiation will increase the avalanche danger to HIGH in the alpine during the hottest part of the day.

Summary

Confidence

High

Weather Forecast

A high pressure ridge continues to bring warm, sunny weather to this region. Freezing levels are expected to remain as high as 3000 m through Friday. On Saturday, a very minor low pressure system moves through, bringing cloud cover and possibly some flurries. Winds are expected to be moderate from the southwest and we should see a slight lowering of the freezing level to around 2500 m. On Sunday, expect a mix of sun and cloud and freezing levels around 2300 m.

Avalanche Summary

On Tuesday and Wednesday 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.

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 - Very 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

Very Likely - Certain

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

Possible - Likely

Expected Size

3 - 6

Valid until: Apr 1st, 2016 3:00PM