Avalanche Forecast

Issued: Dec 27th, 2015 8:09AM

The alpine rating is moderate, the treeline rating is moderate, 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, the weak layer from early December may still be reactive.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

A few centimetres of snow are expected on Monday, before a shift to a cool, dry spell. Expect light northerly winds and a mix of sun and cloud on Tuesday and Wednesday.For more details check out http://www.avalanche.ca/weather.

Avalanche Summary

On Wednesday, two skier accidental avalanches were reported in the Golden backcountry. The first occurred in the morning and was a size 2 wind slab avalanche 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 occurred in the afternoon and 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, only small loose dry avalanches 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 on slopes lee to the SW. Between 40 and 100 cm below the surface you'll probably find a weak layer which was buried in early December. Between 1400 m and 1800 m, this layer consists primarily 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.

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

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A prominent layer of buried surface hoar can be found between 1400 m and 1800 m. A weak crust/facet/surface hoar layer is also expected to still be reactive in isolated areas at higher elevations. Smaller avalanches may step down to these layers.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 28th, 2015 2:00PM