Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.
Weather Forecast
There is a break in between storms today, with only trace amounts of snow forecast, alpine temps rising to -3 and ridge top winds SW-20 gusting to 60 km/h. Freezing levels today will be ~1200m. The next system will hit the park on Saturday, expect around 5 cm of snow on Saturday and Sunday. Snow continues through the forecast period till Tuesday.
Snowpack Summary
35-45cm of storm snow sits over the December 8 surface hoar layer at lower elevations and over variable wind slabs up high. The storm snow is mainly low density with some soft slab developing as temps warm. The November 28 surface hoar layer is down around 50-65cm over a facetted mid-lower snowpack. The Nov 12 surface hoar layer is down 70-120cm.
Avalanche Summary
4 size 2-2.5 natural slab avalanches were observed from steep terrain off Mt Tupper and Mt MacDonald on the highway corridor. One natural avalanche, size 3 was also observed yesterday from a north aspect, likely triggered by wind loading. Sluffing of the low density surface snow was observed in unsupported terrain, steeper than 35 degrees.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
Problems
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.
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.