Avalanche Forecast

Issued: Dec 15th, 2015 8:27AM

The alpine rating is moderate, the treeline rating is low, 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 possible. Start with small test slopes and build up slowly to bigger features. There is still a lot of uncertainty associated with this early winter snowpack.

Summary

Confidence

Moderate

Weather Forecast

Fairly benign weather is expected through the forecast period. WEDNESDAY: Flurries overnight, light northwest winds, -10 at 1500m. THURSDAY: no snow is expected, light to moderate south winds, -10 at 1500m, FRIDAY: Flurries, light west winds, -10 to -15 at 1500m.

Avalanche Summary

Avalanche activity appears to have tapered off since the weekend. Avalanche professionals in the field are reporting sluffing in steep terrain in response to skier traffic (aka good riding conditions) and some lingering reactive pockets of wind slab in steep lee features. No new avalanches have been reported on the layer of buried surface hoar since last week, however, people have been experiencing wumphing and other signs of instability from safe terrain as they travel between 1400 and 1800m.

Snowpack Summary

There is apparently very little wind effect in the alpine. About 15 to 40cm of snow now 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. It 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 sudden planar, resistant planar and sudden collapse 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 at and below tree line and remains sensitive to human triggering. It is most widespread 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

Wind Slabs

Small pockets of wind slab can be found in ridge loaded lee features

Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 16th, 2015 2:00PM