Avalanche Forecast

Issued: Feb 14th, 2016 7:26AM

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

jlammers, Avalanche Canada

Purcells.

Triggering large persistent slab avalanches is still possible, especially in the north of the region. Remain diligent and continue to make conservative decisions.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

SUNDAY NIGHT: 5-15cm of new snow / Strong southwest ridgetop winds / Freezing level at about 1400mMONDAY: Mix of sun and cloud / Moderate ridgetop winds / Freezing level at about 1200mTUESDAY: 5-15cm of new snow falling mostly in the early morning - easing by mid day / Strong southwest ridgetop winds / Freezing level at about 1400mWEDNESDAY: Mix of sun and cloud with isolated flurries / Light southwest ridgetop winds / Freezing level at about 1000m

Avalanche Summary

Observations have been extremely limited in the last few days, although a natural Size 1.5 avalanche was observed in the Golden Backcountry on Thursday that apparently ran on a reloaded bed surface in a wind loaded feature. The interface is suspected to be the early January weak layer. Natural persistent slab avalanche activity was also observed earlier in the week, with a report of two Size 2.5s also in the Dogtooth Range that also released on the surface hoar, facet and crust weakness as deep as a meter down. Light amounts of new snow and strong southwest winds are expected to form new wind slabs on Sunday night.

Snowpack Summary

On Sunday night, generally light amounts of new snow are expected to fall, and strong southwest winds are expected to form new wind slabs in lee features at treeline and in the alpine. The new snow will overlie wind slabs which formed throughout the weekend. About 10-30 cm below the surface, you'll likely find a melt freeze crust which exists in most places except for in high elevation shaded terrain. The early January surface hoar/ facet layer is typically down 70-90 cm. Recent avalanches have been failing on this interface in the north of the region (see avalanche discussion) and it continues to produce sudden planar results in snow pit tests. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Problems

Wind Slabs

New wind slabs are expected to form on Sunday night in response to light amounts of new snow and wind. Watch for triggering in the lee of ridgecrests at treeline and in the alpine.

Travel on ridges to avoid freshly wind loaded features. >Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A weak mix of surface hoar and facets remain a concern, especially in the Dogtooth Range in the north of the region. A cautious approach is required in this area, as this layer may still surprise with nasty consequences.

Be cautious around open slopes and convex rolls at and below treeline where buried surface hoar may be preserved. Big alpine features are also suspect.>Avoid thin, rocky or sparsely-treed slopes.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 15th, 2016 2:00PM