We are tracking an incoming storm and there is a high degree of variability in the modeling of snowfall amounts and wind. The hazard will increase rapidly if we receive strong Westerly winds and heavy snowfall.
Weather Forecast
Temperatures are cooling but will remain mild. Freezing levels dropping back down to below 1700m. Forecasted snowfall amounts are decreasing, but we still expect 15-30cm by the end of the week in the Columbia Icefields area, with the heaviest precipitation arriving later in the week. Moderate to strong Southwest winds expected with the snowfall.
Snowpack Summary
Midpack is gaining strength with recent mild temperatures. Bonding with the November crusts near the bottom of the snowpack appears to be improving. New windslabs are forming in specific lee and cross loaded terrain with recent steady SW winds. Whumphing is less dramatic and more localized than the previous week.
Avalanche Summary
Dec 9 - Numerous loose dry slides to size 1.5 on steep solar aspects at treeline elevation (2100m) and up to 2400m. Several thin, soft windslabs to sz 1.5 slid naturally in cross loaded features near ridgetops on Medicine slab. One skier accidental wind slab was reported from Hilda Peak - 30cm deep, 40m wide, running 15m - 2400m, South East aspect.
Confidence
Intensity of incoming weather systems is uncertain
Problems
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.
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.