Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Monday: Trace amounts of snow / light northwest winds / freezing level @ 1100m Tuesday: Light snowfall during the day increasing to heavy snowfall in the evening / strong to extreme westerly winds / freezing level @ 1100m Wednesday: Light snowfall / strong westerly winds / freezing level@ 800m
Avalanche Summary
Widespread natural, human triggered, and explosive triggered avalanche activity was observed in the Whistler area on Saturday. The avalanches were up to size 2.5 and occurred in response to Friday night's storm. A size 2 skier-triggered slab avalanche occurred on a steep, lee alpine feature in the Spearhead Range on Sunday. My feeling is that isolated human-triggered avalanches up to size 2 will be possible at all elevation bands on Monday.
Snowpack Summary
Heavy snowfall and strong winds on Friday night created new wind and storm slabs and continued to cover an assortment of old snow surfaces that were first buried a little over a week ago. These old surfaces are now about 45cm down and include crusts that exist on all aspects at lower elevations and on steep solar aspects higher up. Facets and spotty surface hoar may also exist in combination with crusts, so there may be continued slab reactivity at lower elevations. The mid and lower snowpack are strong and well settled. The average treeline snowpack depth is about 240cm.
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.
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.