Avalanche Forecast

Issued: Dec 28th, 2015 8:08AM

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.

pgoddard, Avalanche Canada

Purcells.

Conditions are variable across the Purcells. In isolated areas, a persistent weak layer may still be reactive to human triggers. Take the time to investigate your local snowpack.

Summary

Confidence

Moderate

Weather Forecast

A cool, dry spell is starting. Expect light northerly winds, a mix of sun and valley cloud and cool temperatures for the foreseeable future.For more details check out http://www.avalanche.ca/weather.

Avalanche Summary

On Wednesday, two avalanches were triggered by skiers in the Golden backcountry. The first was a size 2 wind slab which occurred on a northwest aspect at about 2400 m. It was up to 50 cm in depth and ran approximately 600 m. The second was a size 2.5 wind slab at ridgetop. This also occurred on a NW aspect at 2400 m elevation. This avalanche stepped down to a deeper layer lower down in the start zone, likely the early December interface. On Thursday, a large settlement was felt in a flat meadow in the Invermere backcountry. This occurred at 2200 m in a below treeline terrain feature and the failure layer is unknown. Since then, several small loose dry avalanches and one size 1.5 wind slab have been observed.

Snowpack Summary

20-30 cm of low-density snow typically overlies a well-settled mid and lower snowpack. Surface hoar and near-surface facets may be mingled with a few cm dry new snow. Wind slabs may be found in the lee of ridges and ribs. Between 40 and 100 cm below the surface you'll probably find a weak layer which was buried in early December. At and below treeline, this layer mainly consists of large surface hoar. At higher elevations, this layer consists of a sun crust, facets, and/or small surface hoar. This layer is still reactive in some snowpack tests and has produced at least one human-triggered avalanche in the last week. The layer is creating a low probability, high consequence type of problem, especially in the north of the region. Below this layer, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

Soft wind slabs may be reactive to the weight of a person below ridges and ribs.

Use ridges or ribs to avoid pockets of wind loaded snow. >Be cautious as you transition into wind affected terrain. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Buried surface hoar can be found below treeline. A weak crust/facet/surface hoar layer may also still be reactive in isolated areas at higher elevations. Smaller avalanches may step down to these layers.

Conditions are greatly improved, but be mindful that persistent weak layers are still present. >Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 29th, 2015 2:00PM