Avalanche Forecast

Issued: Mar 2nd, 2014 8:05AM

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

jlammers, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Monday: Light to locally moderate snowfall / Moderate to strong southerly winds / Freezing level at 1200mTuesday: Light to locally moderate snowfall / Moderate to strong southwest winds with extreme gusts / Freezing level at 1200mWednesday: Mix of sun and cloud with a possibility of flurries / Light ridgetop winds / Freezing level at 800m

Avalanche Summary

In the Dogtooth Range on Friday, skiers initiated a cornice fall which triggered a size 2.5 slab avalanche on the slope below. In the same area on Saturday a size 2 slab was rider triggered from a ridge crest. A size 2 natural slab avalanche was observed on Saturday further south in the region. The February 10th interface is thought to have been the culprit in all of these events.

Snowpack Summary

Light amounts of new snow are expected to overlie weak surface hoar in sheltered areas, a sun crust on solar aspects and thin wind slabs in exposed terrain. These new accumulations are likely to be reactive as a wind slab in pockets of exposed terrain.The big news remains a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 50 and 120cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, destructive avalanches are still a very real concern with ongoing reports of human triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering has now become unlikely.

Problems

Persistent Slabs

A deep and destructive slab overlies a variety of weak layers and rider triggering continues throughout the region. Conservative terrain selection is critical to safe mountain travel.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Moderate to strong winds are expected to blow new accumulations into pockets of wind slab in exposed lee terrain. These new accumulations will overlie existing thin wind slabs which have been reactive in recent days.

Be cautious as you transition into wind affected terrain.>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

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 3rd, 2014 2:00PM