Avalanche Forecast

Issued: Dec 18th, 2015 3:00PM

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.

esharp, Avalanche Canada

Purcells.

The new snow may be hiding pockets of old wind slab on south aspects with new soft slabs developing on north facing lee features through the day.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

SATURDAY: no significant precipitation is expected, moderate westerly winds, accompanied by a warming trend with a high of -5C at treeline. SUNDAY: light snow with accumulations of up to 5cm by the end of the day, moderate southerly winds, -5C at treeline. MONDAY: isolated flurries, light southerly winds, temperatures are forecast to fall to -10C at treeline through the day.

Avalanche Summary

Avalanche professionals in the field are reporting small slab avalanches in the immediate lee of wind loaded features.

Snowpack Summary

Variable winds have produced localized wind effect in the new snow at ridgeline. About 15 to 40cm of snow sits above a crust that extends up to 1800m. A more extensive persistent week layer is buried between 30 and 80cm down. The form of this layer varies depending on aspect and elevation: it can be found as a crust on south facing slopes in the alpine, or as large grained surface hoar and facets below tree-line. The surface hoar is most widespread in an elevation band between 1400m and 1800m although it may extend higher south of Invermere. Snow pit tests suggest that human triggering of this interface is still possible, although unlikely. Below this the snowpack is thought to be mainly well settled.

Problems

Wind Slabs

Variable winds and an abundance of low density snow available for transport will continue to produce wind slabs in lee features. Look for shooting cracks as a sign you entering wind a wind loaded feature.

The recent snow may now be hiding windslabs that were easily visible before the snow fell.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

A layer of buried surface hoar can be found between 1400m and 1800m. Watch out for signs of instability like wumphing to guide you through this elevation band.

Avoid open slopes, convex rolls, burns, cutblocks and terrain traps when traveling below tree-line. This is where buried surface hoar is best preserved and most volatile.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Dec 19th, 2015 2:00PM