Avalanche danger could increase dramatically through Thursday night if the snowfall exceeds the forecasted amount.
Weather Forecast
Weather forecasts indicate up to 15-20cm of snow starting Thursday night in the Icefields area while lesser amounts will be seen in Jasper and the Maligne lake area. Temperatures will remain warm through Thursday and then drop to -15 - 20 C overnight on the weekend.
Snowpack Summary
The snowpack is characteristic of early season conditions, with a weak structure and highly variable distribution. The Icefields area snowpack consists of several supportive windslabs over basal facets. Test results confirm that if a windslab layer releases in the upper snowpack, it could collapse the basal facets and slide full depth to ground.
Avalanche Summary
On December 31, several new slab avalanches were observed on cross loaded features at tree line and above. A skier accidental size 1.5 slab occurred at treeline on a Northeast aspect in an open slope. The skier went for a short ride and was buried waist deep.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Thursday
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.
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.