Avalanche Forecast

Issued: Dec 16th, 2018 4:39PM

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

Avalanche Canada kdevine, Avalanche Canada

Have patience with this recent storm snow. It is going to take some time for things to stabilize. The potential for human triggered avalanches remains likely! Choose low angle terrain and avoid overhead hazard.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

SUNDAY NIGHT -Flurries, up to 5 cm / south to southwest winds, 25-50 km/h / alpine low temperature near -4MONDAY - Cloudy with flurries, 5-10 cm / southwest winds, 25-50 km/h, gusting to 60 km/h / freezing level 1600 m / alpine high temperature near -5TUESDAY - Snow, 10-20 cm / southwest winds, 20-50 km/h, gusting to 60 km/h / freezing level 1500 m / alpine high temperature near -4, low temperature near -6WEDNESDAY - Mainly cloudy with flurries, up to 10 cm / west to southwest winds, 20-40 km/h, gusting to 60 km/h / freezing level 1500 m / alpine high temperature near -5, low temperature near -8

Avalanche Summary

Avalanche activity has been extensive in the Purcells over the past 5 days with daily reports of natural and explosive triggered avalanches to size 3.5, and human triggered avalanches to size 2.5. Many of these have been remote triggered (triggered from a distance).One very notable report on Saturday was a size 2.5 human triggered avalanche that was remotely triggered from 50-100 m away on a northwest aspect at 2250 m. A report of this avalanche can be found on the Mountain Information Network. (here)A natural avalanche cycle to size 4 was also reported in the region on Friday.

Snowpack Summary

60-120 cm of snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south facing slopes). Strong winds have promoted widespread slab formation.Another layer of surface hoar and sun crust is now buried 80-150 cm. The potential may exist for smaller avalanches to step down to this deeper layer, resulting in very large avalanches. The most likely areas for this layer to be a problem is where the surface hoar sits on the sun crust, which is most likely on steep south facing terrain at treeline.At the base of the snowpack is a crust that formed in late October. This layer is likely only a problem on large, steep alpine features with a shallow snowpack. It would likely take a large trigger, such as a cornice fall, to produce an avalanche on this layer.

Problems

Persistent Slabs

An icon showing Persistent Slabs
60-120 cm of new snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals) and sun crust (on south facing slopes). Wind loaded pockets could have 200+ cm of snow over this layer.
Use conservative route selection, choose low angled and supported terrain with low consequence.Remote triggering is a concern, watch out for adjacent slopes.Avalanches on this layer may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 3

Valid until: Dec 17th, 2018 2:00PM