The hazard may go higher than forecast in the afternoon with solar heating. Cornice failure is a real concern with these spring conditions.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Cloudy tonight with the possibility of a few snow showers as the last of a Pacific frontal system tracks east and south of the region. Sunny with cloudy periods for the remainder of the forecast period. Winds light and variable for the next few days, with the freezing level rising to 2000m by Thursday afternoon.
Avalanche Summary
Moist loose avalanches reported on solar aspects below 1900m. No other reports from the area. Cornices are now becoming a concern as the Spring temperatures progress.
Snowpack Summary
20-30 cm of low density storm snow is sitting on a strong and supportive rain crust that was buried last Saturday and extends as high as 2100m. West through southwesterly winds have shifted these new accumulations into wind slabs in lee terrain, especially high NE aspects. A facet/crust layer that was buried in mid-March is now approximately 50-100 cm down. It was found down 55 cm near the Duffey Lake Road, and produced moderate sudden results. This remains a serious concern in the region because of it's potential for very large avalanches. Cornices are now large and mature and may collapse with warming and spring-like temperatures. Moist snow has been reported on all aspects up to 1800m
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.