Avalanche Forecast

Archived

Jan 1st, 2014–Jan 2nd, 2014

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

A number of significant avalanches have occurred in the north of this region and just beyond its northern boundary. Check the forecaster blog. Use caution if traveling in the backcountry at this time.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Thursday: An incoming storm will build through the day and likely peak some time in the late afternoon. Around 10 cm new snow likely by the afternoon. Freezing levels rising briefly to around 1300 m. Winds gusting to 50 km/h from the SW at ridgetop.Friday: Light precipitation in the morning with a few more cm or so of new snow. Freezing levels should fall back to surface, with treeline temperatures of around -7C. Winds 20-30 km/h from the NW.Saturday: A clearing trend with some sunny breaks. Temperatures falling to around -10C. Winds increasing from the NW in the afternoon at all elevations as arctic air starts to descend from the north.

Avalanche Summary

A number of significant avalanches have been reported from the north of this region and just beyond its boundary to the north. One very large (size 3) avalanche was reported on Tuesday on a N aspect at 2200 m from relatively gentle terrain with a fracture depth of 100 cm. Two large (size 2) avalanches were reported from near Golden on Monday, likely triggering buried surface hoar from 10-Dec down around 50 cm. A size 3 natural avalanche was reported from the Bugaboos on Sunday on a NE aspect at 2650m, triggered by a cornice release that pulled out a large slab all the way to ground on the slope below. Outside the boundary of this region to the north of Golden, there was an incident in the Hope Creek drainage, where four people were involved (with two sustaining injuries) in a size 3 avalanche in an alpine feature on a NE aspect.

Snowpack Summary

Up to 25 cm of recent storm snow has been redistributed by moderate to strong northwest and southwest winds. In the upper metre of the snowpack a couple of persistent weak layers exist. The upper one comprises surface hoar and is buried around 40-50 cm. The lower one comprises a facet/crust combo and is buried 80-100 cm. Both interfaces give variable results with snowpack tests, but professional operators are treating them with caution.A bigger concern, especially in the Northern part of the region is a layer of weak sugary depth hoar crystals at the base of the snowpack that lie above a crust from early October. Several large avalanches in the last 10 days have been attributed to failures at this layer. Wide propagations on relatively gentle terrain have been noted, as well as a tendency for seemingly disconnected slopes to become connected by one large avalanche.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.