Storm slabs are expected to remain a problem above treeline Friday. A rising freezing level combined with the strong kiss of the spring sun is expected to initiate a round of loose wet activity too. Stay alert to changing conditions!
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Sunday
Weather Forecast
The steady progression of ridges and troughs continues. Friday ushers in a brief drying day before another upper trough begins to spread high cloud to the Sea to Sky Saturday giving way to convective flurries on Sunday. FRIDAY: Freezing level around 1500 m, no significant precipitation expected, light northwest wind. SATURDAY: Freezing level around 1500 m, no significant precipitation expected, light southwest wind. SUNDAY: Freezing level around 1200 m, 5 to 15 cm of snow possible, light southwest wind. For more detailed mountain weather information visit avalanche.ca/weather
Avalanche Summary
Reported avalanche activity on Wednesday was limited to very thin & small storm slabs. I suspect that there were some natural storm slab failures on Thursday.
Snowpack Summary
12 to 20 cm of storm snow fell Wednesday night and Thursday accompanied by moderate south/southwest wind which has likely formed storm slabs at and above treeline. Below the new snow the snowpack is strong and well-settled throughout with no notable persistent weaknesses. Cornices are huge and fragile.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.