Check out our blog post that addresses the current forecast challenges and changing conditions this weekend: http://www.avalanche.ca/cac/bulletins/forecaster-blog
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
A storm moving tracking along the international border will deliver snow through the night Friday, extending into Saturday. 10 - 20 cm of snow is expected and will likely be accompanied by moderate/strong SW winds. Storm activity should taper off Saturday evening. Freezing levels are expected stay near 1000m Saturday. A weak trough passes over the region Sunday bringing broken cloud cover and the occasional flurry of snow.
Avalanche Summary
A few thin windslabs were triggered Thursday by skiers, but the bulk of the avalanche activity yesterday was limited to sluffing of the new snow.
Snowpack Summary
Five centimeters fell overnight Thursday, burying the February 16th Surface Hoar. 20 cm of light density snow lies between the February 16th surface hoar and the February 8th weakness. Within that 20cm some places have at least one other layer of surface hoar that formed between snowfalls. Feb. 8th is used to describe a combination of weak layers: In most locations it marks a widespread surface hoar layer. On steep south & west facing aspects a crust that formed during the drought was also buried on Feb. 8th. This crust likely has a bit of faceting below it too, meaning that most terrain in the region has a weak layer 20 - 25 cm under the snow surface. Down below this problematic interface a well settled mid pack is in place. The exception is the eastern and southern parts of the region where deeper weaknesses and basal facets may still be a factor. In these areas, a low-probability/high-consequence condition exists. It should be noted that large cornices remain widespread throughout the region.
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.
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.