Avalanche Forecast

Issued: Dec 28th, 2017 5:03PM

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

There will continue to be a slow accumulation of low density new snow in the coming days.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

FRIDAY: Flurries, accumulation 5cm during the day and another 5-10cm overnight / Light south southwest wind / Alpine temperature -11 SATURDAY: Cloudy with isolated flurries / Light to moderate west wind / Alpine temperature -12 SUNDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -10

Avalanche Summary

Recent reports continue to show both natural and human triggered loose dry avalanches in steep terrain to size 1 in areas that have not been affected by wind. Additionally isolated wind slab avalanches have been reported in the alpine to size 1. Expect continued potential for triggering loose dry avalanches in steep terrain and consider the potential to trigger persistent slabs where last week's storm snow has settled into a cohesive slab.

Snowpack Summary

Low density new snow is beginning to accumulate and bury 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 down approximately 30-50cm. The bond at this old snow interface is of critical importance where the overlying storm 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 and any area where the surface hoar may have formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this layer but suggest that it may be most reactive on northerly aspects.  A rain crust that formed in late November is now buried 60-100cm deep. Recent reports show this layer to be unreactive at this time.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent northwest, west and southwest winds have created wind slabs in the lee of terrain features.
Travel on ridges and/or ribs to avoid wind loaded slopes belowBe cautious as you transition into wind affected terrain.

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 may be reactive 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 whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

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