Heavy snowfall this weekend will create very dangerous avalanche conditions.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
SATURDAY: 15-30 cm of new snow, 20-40 km/h southwest winds, treeline temperatures -2.SUNDAY: 5-10 cm of new snow, light west winds, treeline temperatures -2.MONDAY: Sun and cloud, light northwest winds, treeline temperatures -5.
Avalanche Summary
On Thursday, avalanche activity was limited to minor sluffing in steep terrain. With heavy snowfall and strong winds in the forecast, widespread storm slab activity can be expected for the weekend.
Snowpack Summary
Forecast snowfall amounts are uncertain, but expect 20-40 cm of fresh snow by Saturday afternoon. The new snow is falling on a variable surface that includes settled snow on southerly aspects, loose snow on shaded aspects, isolated pockets of surface hoar, and sun crusts on steep solar aspects. Overall the incoming snow will likely bond poorly to this interface. The thickest and most touchy storm slabs can be expected on north-facing wind-loaded features. A rain crust exists 30-50 cm deep, and recent reports suggest the storm snow may still be poorly bonded to the crust on shady north aspects. Below the crust, the snowpack is settled and strong. Total snowpack depths are 160-200 cm at treeline.
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.