Things have changed significantly in the last 48 hours. Intense South West winds have redistributed cold dry snow and created a touchy windslab condition.
Weather Forecast
The calm and very cold weather of the last 2 weeks is over. Milder temperatures expected, with strong SW winds and steady precipitation (25cm possible by Friday in the Columbia Icefield area).
Snowpack Summary
Significant change in the last 48 hours due to intense SW winds and ridge top transport of faceted snow. Expect new wind slabs in lee areas and cross loaded gullies. Suspect surface hoar (Dec 11) in sheltered NE aspects around treeline (2100-2300m). Nov crust is now on the surface in scoured areas and as deep as 1m+ on lee aspects.
Avalanche Summary
Numerous natural wind slabs to sz 1.5 observed today, particularly in alpine gulley features and steep NE aspects. We expect that natural activity was fairly widespread in these types of terrain features, but become quickly obscured and re-loaded. Of note, one size 2 with impressive propagation (~250m) observed on Parker slab, NE, at 2200m.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.