Avalanche Forecast

Issued: Feb 16th, 2015 7:35AM

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

Peter, Avalanche Canada

Purcells.

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Summary

Confidence

Good - The weather pattern is stable

Weather Forecast

A ridge of high pressure will maintain mostly sunny skies through Wednesday. Freezing levels bounce between valley bottom overnight and 1500-2000 m during the day. It could be even warmer on Wednesday with an above freezing layer near 2500 m. Winds are generally light gusting to moderate from the W-NW. The ridge flattens slightly late on Wednesday and allows a weak system to cross the province on Thursday. This could bring a few centimetres of snow, more cloud, and slightly cooler temperatures.

Avalanche Summary

No new avalanches were observed on Sunday. However, there were a few more reports of previous activity with slabs up to size 3. Sunshine and daytime warming could trigger loose wet sluffs, cornice collapses, and isolated deeper slabs this week.

Snowpack Summary

Expect to find surface crusts on solar aspects and all aspects to at least 2000 m. At alpine elevations, thin new wind slabs or storm slabs may be found and cornices are large and weak. Underneath newly formed near-surface crusts, you may find moist snow. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive and still the main concern in many areas. The mid-January surface hoar, deeper again, remains problematic in some areas. The mid-December weak layer may still be on the radar in isolated areas in the east. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It seems to have been reawakened with warming and has been triggered by explosives during the recent warm spell, taking the entire snowpack with it.

Problems

Wind Slabs

Fresh wind slabs may be lurking behind ridges and terrain features. Cornices are also large and weak and could collapse.

Give cornices a wide berth when travelling on or below ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Persistent slabs are most likely to be triggered from thin snowpack areas, or with large triggers like cornice fall or an avalanche stepping down.

Do not travel on slopes that are exposed to cornices overhead.>Avoid common trigger points like convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Loose Wet

Expect loose wet sluffs on steep sun-exposed slopes. These could trigger persistent weaknesses if they gain significant mass.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 17th, 2015 2:00PM