Avalanche Forecast

Issued: Dec 17th, 2015 8:26AM

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

esharp, Avalanche Canada

Purcells.

It sounds like good riding conditions out there but large human triggered avalanches are still possible bellow tree-line. At upper elevations watch for wind slabs developing through the day.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

FRIDAY: 2-5cm of new snow, moderate to strong southwesterly winds, -5C at treeline .SATURDAY: no new snow expected, light westerly winds, -7C at treeline. SUNDAY: Light flurries, moderate southwesterly winds, - 10C at treeline.

Avalanche Summary

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

Snowpack Summary

It sounds like good riding conditions out there with mainly low density snow on the surface. There is some localized wind effect in the new snow at ridgeline. About 15 to 40cm of snow sits above a crust that extends up to 1800m. The early December persistent weak layer can now be found down 30-80cm. This layer can be found as an old sun crust on solar aspects in the alpine, or as large grained surface hoar and small facets in isolated pockets bellow treeline. The surface hoar is mainly a problem between 1400m and 1800m, although it may extend higher in the south of Invermere. Snow pit tests on this interface have been widely variable; producing a mixture of sudden and resistant failures or no results. The mid and lower portions of the snowpack are thought to be mainly well settled.

Problems

Persistent Slabs

A layer of buried surface hoar can be found bellow tree-line, between 1400m and 1800m. It remains sensitive to human triggering. 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

Wind Slabs

Wind slabs are expected to develop at tree-line and in the alpine as the wind picks up through the day.

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

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 18th, 2015 2:00PM