Avalanche Forecast

Issued: Feb 19th, 2015 7:10AM

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

Peter, Avalanche Canada

Purcells.

Hazard is generally low; however, give cornices respect when travelling in the alpine. They are a stand-alone hazard but could also be a potential trigger for deep slabs.

Summary

Confidence

Good

Weather Forecast

We should see a couple more days of mainly cloudy skies with light flurries before the ridge of high pressure rebuilds returning the province to sunny conditions by late Saturday or Sunday. The freezing level is around 1500 m on Friday and lowers to just under 1000 m on the weekend. Winds are light gusting to moderate from the NW on Friday and switch to north-easterly for the weekend.

Avalanche Summary

Over the past several days there have been reports of natural and explosive triggered slabs and cornice falls to size 3. Almost all of these slides occurred on high alpine slopes with cornice related activity being specific to NE-E slopes below ridges. On Tuesday there were also reports of fresh wind slabs (10-20 cm thick) being reactive to skier traffic.

Snowpack Summary

Expect to find surface crusts on solar aspects and all aspects to at least 2000 m. At alpine elevations, thin new wind slabs or storm slabs may be found and cornices are large and weak. Underneath newly formed near-surface crusts, you may find moist snow. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive and still the main concern in many areas. The mid-January surface hoar, deeper again, remains problematic in some areas. The mid-December and mid-November weak layers of crusts and facets can still be found near the bottom of the snowpack, particularly in shallower eastern parts of the Purcells.

Problems

Wind Slabs

Pockets of wind slab may still be reactive in steep lee terrain or cross-loaded gully features in the alpine. Cornices are large and potentially weak and should be given a wide berth.

Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Buried persistent weaknesses are largely dormant but could still be triggered by a large load (i.e. cornice fall) or from areas with a shallow or variable snowpack.

Avoid common trigger points like convexities or areas with a thin or variable snowpack.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 20th, 2015 2:00PM