Special attention to wind loaded terrain is necessary until the storm and wind slabs bond to the weak layers below.
Confidence
Fair - Due to the number and quality of field observations
Weather Forecast
Monday: Temperatures should lower slightly on Monday after the passing of the remnants of the Pacific frontal system on Sunday. Light precipitation, (2 to 5 cm), expected.Tuesday: Freezing levels will go up on Tuesday with light to very light precipitation expected, light to moderate sw winds at ridge tops.Wednesday: 2 to 5cm of precipitation with light winds from the west-south west, then temperatures going down as an arctic air mass in the north reaches down into the southern part of the Province.
Avalanche Summary
Wind slabs overlying surface hoar and facets have become touchy. The possibility of triggering large and destructive avalanches is high. Recent reports speak of shooting cracks and widespread propagation in the storm and wind slabs. The potential exists for large destructive avalanches with increased loading and wind transport.
Snowpack Summary
Recent dribs and drabs of snow are adding to the snowpack surface load. Snowpack depths at tree line currently vary from 100- 130 cm with the highest variability in wind-exposed areas. A persistent weakness of buried surface hoar and facets, is down approximately 20-40cm . This layer has been producing variable results with snowpack tests. Recent reports indicate that the new storm slab is becoming reactive with warming temperatures and additional loads. At the base of the snowpack are weak facets and depth hoar combined with a crust from early October.. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex slopes. At lower elevations the snow depth is below the threshold for avalanches.
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.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.