Storm and wind slab avalanches will become more likely and larger with continued strong winds, snow and warming temperatures.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
FRIDAY: Snow flurries with another 5-10cm of accumulation. Moderate SW winds. Temperatures starting to cool with freezing level lowering to around 900m.SATURDAY: Cloudy with scattered flurries bringing another 5cm. Light southerly winds and freezing levels dropping to 700 m.SUNDAY: Cloudy with scattered flurries bringing another 5cm. Light southerly winds and freezing levels dropping to 500 m.
Avalanche Summary
Reports from Wednesday include several skier and explosives triggered storm slab avalanches up to Size 1.5 and natural soft wind slab avalanche up to Size 2. Of note was one remotely triggered Size 1.5 30cm thick wind slab avalanche from a skier 7m away that ran on facets overlying a crust that formed mid-February.
Snowpack Summary
20-50 low density fresh snow is bonding poorly to previously wind-affected surfaces (e.g. scoured crust, hard sastrugi, or stubborn wind slabs) in exposed areas, or around 20 cm of faceted snow in sheltered areas. Strong southerly winds have scoured wind-exposed slopes and deposited deep drifts on lee aspects. A crust from mid-February is below all this, down around 50-70cm. Recent snowpack tests have been giving moderate sudden results in facets above this crust. The mid and lower snowpack are well settled and strong.
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.