Weather Forecast
A firmly embedded ridge of high pressure over Alberta seems to be causing systems to fizzle once they reach the Columbia Mountains. On Friday light snowfall is expected but should taper-off with only trace amounts forecast for Saturday/Sunday. Winds should be light and west/northwesterly throughout the period with freezing levels peaking at about 1100m.
Avalanche Summary
Avalanche activity over the past few days has been mostly limited to cornice fall and isolated small windslabs.
Snowpack Summary
Very warm alpine temperatures from last weekend melted snow surfaces and a crust now exists to ridge top on solar aspects. In general, the upper snowpack is now well settled and riders are shredding pretty much everything. The exception may be isolated wind slabs that formed at higher elevations with moderate alpine winds on Monday/Tuesday. Deeper weaknesses in the snowpack seem to less of a concern; however, in the southern end of the region there is still talk of basal facets as some operators are avoiding thin and rocky alpine features. This represents a very low probability-high consequence scenario. Large, unstable cornices are also widespread in the alpine. A dusting of new snow now sits on weak snow crystals that developed during the week (surface hoar/crusts/facets). This will be the thing to watch as the overlying slab evolves.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.