Forecast snowfall amounts are highly variable for Saturday night with highest amounts expected in the south of the region. Pay close attention to how much snow falls in your riding area, and be prepared to back off to mellow terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Saturday
Weather Forecast
Saturday night and early Sunday morning: 5-15cm of new snow / Strong southwest winds / Alpine temperatures at -8. Sunday: Generally clearing skies / Light north winds / Alpine temperatures at -12. Monday: Clear skies / Light variable winds / Alpine temperatures at -12. Tuesday: Clear skies / Light north winds / Alpine temperatures at -14
Avalanche Summary
At the time of publishing this bulletin, avalanche observations were highly limited. With the new snow and strong southwest winds on Friday night, I'm sure there was evidence of wind slab activity at treeline and in the alpine, especially in the south of the region (Tantalus/ Diamond Head/ Tricouni) where snowfall amounts were greatest. Looking forward to Sunday, continued snowfall and strong winds will continue to promote ongoing wind slab activity.
Snowpack Summary
As of Saturday about 15cm of recent storm snow had been redistributed by strong southwest winds into reactive wind slabs in higher elevation terrain. With more snow and wind forecast for Saturday night, this developing slab will only increase in size and destructive potential. Below the recent storm snow you may find a layer of buried surface hoar which formed during last week's clear weather, although the size and distribution of this layer is largely unknown at this time. The mid-November melt-freeze crust is widespread and is buried anywhere from 20-200 cm depending on aspect and elevation. Although snowpack tests have shown this layer to be mainly unreactive, I'd expect increased reactivity with this layer in shallow, wind-affected alpine start zones.
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.