Confidence
Fair - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
Thursday: Snow with 15-20cm of accumulation, moderate to strong SW alpine winds and freezing levels around 1200m. Friday: A mix of sun and cloud with isolated flurries, moderate NW winds and freezing levels dropping to 600m. Saturday: Mostly sunny and dry with moderate NW alpine winds and freezing levels in valley bottoms.
Avalanche Summary
A recent report includes observation of a Size 2 storm slab that ran naturally in the past couple of days on a northeast facing alpine slope. Other reports include cracking and whumpfing associated with basal facets on south aspects.
Snowpack Summary
Snowpack depths vary across the region and with elevation, but overall below average for this time of year. Wind-exposed areas are highly variable with scoured areas and deep drifts, and the snowpack below treeline is still mostly below threshold for avalanche activity. A thin raincrust has been found down 20cm at 1900m and down 5cm at 1500m elevation. Small surface hoar down approximately 30cm is still producing easy to moderate shears during snowpack testing. Mid and lower snowpack layers include facets (which may overlie a crust in some areas) and spotty surface hoar in sheltered terrain. In most places the overlying slab seems to be well bonded, but continued settlement could make the slab more reactive before the facets gain strength. Early season riding hazards such as rocks, stumps and logs are lurking below the surface in many areas. In glaciated terrain open and poorly bridged crevasses are everywhere.
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.