As the stormy weather eases off and temperatures drop, the snowpack will begin to gain some strength. However, storm slabs are still likely to be encountered and could be reactive to human triggering, especially in wind loaded areas.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Wednesday
Weather Forecast
SUNDAY NIGHT - Mainly cloudy with scattered flurries / southwest winds, 15-35 km/h / alpine low temperature near -10MONDAY - Cloudy with sunny periods / west winds, 20-25 km/h / alpine high temperature near -10TUESDAY - A mix of sun and cloud with isolated flurries / southeast winds, 15-20 km/h / alpine high temperature near -5 WEDNESDAY - Snow, up to 20 cm / southeast winds, 20-40 km/h / alpine high temperature near -2 / freezing level 1000 m
Avalanche Summary
On Sunday, numerous explosives triggered avalanches up to size 2 were reported in the region. Many of these were cornice failures.On Saturday, numerous natural avalanches to size 3 and explosives triggered avalanches to size 2.5, and one size 1 human triggered avalanche were reported in the region. On Friday, numerous explosives triggered avalanches to size 3 and one human triggered size 1.5 were reported. A group also reportedly remotely triggered a storm slab 20 m away with a 80-100 m crown.A widespread natural avalanche cycle up to size 3, and human triggered avalanches to size 2 were reported in the region on Thursday.
Snowpack Summary
The Sea to Sky region has received approximately 100-140 cm of recent storm snow with strong to extreme southerly winds. Cornices are growing and slab formation is likely widespread.At treeline and below, the storm snow sits on two weak layers that are down 80-100 cm and 150-200 cm. These layers consist of surface hoar (feathery crystals) in more sheltered areas and a crust on solar aspects and on all aspects below 1500m.In the lower snowpack, a weak layer of facets (sugary snow) is now over 200 cm deep. There have been no reports of avalanches on this layer for over a week, but it may still be reactive to heavy loads (such as a cornice fall) in isolated areas.
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.
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.