Avalanche Forecast

Issued: Dec 26th, 2013 8:47AM

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

Avalanche Canada mbender, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Friday

Weather Forecast

Friday: Light to locally moderate precipitation. Alpine temperatures -3. Moderate to strong southwesterly winds switching to northwest in the afternoon. Freezing level 1200mSaturday: Mainly dry with broken skies, winds moderate to strong from the northwest and alpine temperatures -8.Sunday: Light snowfall, alpine temperatures -9, winds light to moderate from the northwest.

Avalanche Summary

A few avalanches to size 1.5 have been reported in the last 2 days. These are isolated to the most recent storm snow. I would expect to see an increase in avalanche activity as wind speeds pick up and new snow amounts accumulate on Friday.

Snowpack Summary

Moderate to strong southwesterly winds have built new wind slabs in alpine and treeline lees. 20-40 cm of new snow sits on a weak layer consisting of surface hoar crystals, stellar crystals and/or crust. Around 60-80 cm below the snow surface, the early December surface hoar, facetted snow, and/or a crust interface sits and has been reportedly more stubborn to rider triggers.The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas. It is now buried 70-90cm below the surface. Snowpack tests vary on this interface with some results producing "sudden" shears and others producing no results. This interface is generally considered to be dormant. However, professional operators are keeping a close eye on it.A weak layer of facets sitting on a crust that formed in October, sits near the base of the snowpack. This layer is predominantly found on north-facing alpine slopes with smooth ground cover. Triggering this weakness is unlikely, however if triggered the resulting avalanche would potentially be a large event with high consequences. Recent reports indicate that the average snowpack depth at treeline is 100-150 cm.

Problems

Wind Slabs

An icon showing Wind Slabs
New snow combined with moderate to strong westerly and southwesterly winds forming windslabs in the lee of terrain features.
Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Buried persistent weak layers exist in the upper 90 cm of the snowpack.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Carefully evaluate and use caution around thin snowpack areas.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

Valid until: Dec 27th, 2013 2:00PM