Avalanche Forecast

Issued: Dec 28th, 2017 4:58PM

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

Avalanche Canada mbender, Avalanche Canada

Low density new snow will continue to accumulate in the coming days.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

FRIDAY: Flurries or periods of snow, accumulation 5 cm overnight Thursday into Friday / Light south southeast wind / Alpine temperature -10 SATURDAY: Flurries, accumulation 5-10cm  / Light southwest wind / Alpine temperature -14 SUNDAY: Mix of sun and cloud / Light southwest wind / Alpine temperature -11

Avalanche Summary

Recent reports show continued observations of wind slabs releasing to Size 1 with skier traffic and ski cutting, primarily on south aspects in the alpine. Additional observations show numerous human triggered and natural loose dry avalanches to size 1 in steep, sheltered terrain. Expect continued potential for triggering loose dry avalanches in steep terrain and consider the potential to trigger persistent slabs as the load continues to increase on top of the mid December persistent weak layer.

Snowpack Summary

10-15cm of low density new snow has buried a recently formed layer of weak feathery surface hoar and/or sugary facets. A layer buried mid-December that consists of surface hoar, sun crust and/or sugary facets is now down approximately 40-60cm.The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, such as sheltered areas at and below treeline, sheltered northerly aspects in the alpine, or anywhere the surface hoar formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this weak layer but suggest that it may be most reactive on northerly aspects. A rain crust that formed in late November is now buried 80-110cm deep. Recent reports from the southwest end of this region suggests it may be reactive in steep, variably loaded terrain features in the alpine.

Problems

Wind Slabs

An icon showing Wind Slabs
Shifting winds have created wind slabs on a variety of aspects.
Be aware of highly variable recent wind loading patterns.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer of surface hoar buried 30-50 cm deep has potential to be reactive in areas where the overlying snow has settled into a cohesive slab.
Approach steep open slopes cautiously at and below treeline where buried surface hoar may exist.Watch for signs of slab formation, such as whumpfing and shooting cracksSluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 29th, 2017 2:00PM

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