Avalanche Forecast

Issued: Feb 17th, 2013 8:12AM

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

Danyelle Magnan, Parks Canada

Glacier.

We are going to be tip-toeing around a touchy surface hoar layer for a while. Periods of sun today may result in loose avalanches and cause trees to shed their snow; enough to trigger slabs up to 55cm deep. Minimize your exposure to avalanche terrain

Summary

Weather Forecast

Light snow and moderate-strong winds should back off this morning as a ridge of high pressure builds bringing increasing sun this afternoon. Periods of sun this afternoon may strong enough to cause trees to shed snow and loose sluffing; which will be enough to trigger the surface hoar layer. Mon and Tues will see increasing cloud and flurries.

Snowpack Summary

Another 20cm snow, mild temps, and S'ly winds are forming a soft slab over a widespread surface hoar layer down 35-55cm. It is most reactive where it is largest; between 1700-1900m; or on steep solar aspects where it sits on a crust. Tests indicate it is likely to be triggered by light loads (easy planar/collapses and RB2 whole block).

Avalanche Summary

There continue to be human triggered avalanches up to size 2 on the most recent surface hoar layer. These have occurred on all aspects and elevations, with the avalanches propagating up to 300m wide and traveling fast and far. Yesterday, over 25 size 1.5-3 natural avalanches occurred from steep confined avalanche paths triggered by wind loading.

Confidence

Problems

Persistent Slabs

A touchy surface hoar layer is down 35-55cm. Human (even tree bomb) triggered avalanches have occurred daily. Avalanches are increasingly possible with new snow and rising winds today adding load, and mild temperatures making the slab more cohesive.

Choose conservative lines and watch for clues of instability.Good group management is essential to manage current conditions safely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Soft windslabs formed on lee slopes above treeline last week from southerly winds. In wind-affected areas the recent storm snow will be more cohesive. These slabs overlay a touchy surface hoar layer and if triggered, avalanches may propagate widely.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 18th, 2013 8:00AM