Avalanche Forecast

Archived

Dec 25th, 2018–Dec 26th, 2018

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Jasper.

Avoid placing yourself under any terrain with cornices overhead as several failures have occurred recently producing large avalanches.

Weather Forecast

Little change is expected in over the holidays, forecasted winds will remain light and variable as arctic air seeps into the region during the next few days. Temperatures will remain cool as the sun traverses low to the horizon with highs of -10C and overnight lows of -17C. A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Last weeks storm snow is providing support underfoot to mountain travelers. Snow conditions at treeline are variable from power, in sheltered areas, to slabs in exposed locations and near ridges. The Dec. 11th persistent weak layer is buried 50-100cm. The deep persistent weakness lingers near the ground in the depth hoar and facets.

Avalanche Summary

Several deep releases from the alpine and been observed in the Icefields area. These avalanches are up to size 3 and appear to have been triggered by cornice failures from South Easterly facing slopes. It is likely these occurred at the interface of last weeks snow and then stepped down to the deep persistent interface at the base of the snowpack.

Confidence

Due to the number of field observations

Problems

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.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.