Watch for wind loaded and cross loaded slopes at higher elevations. We suspect there are weak layers near the base of the snowpack that have the potential to produce large avalanches if triggered by a wind slab release.
Confidence
Low - Due to the number and quality of field observations
Weather Forecast
WEDNESDAY: Mainly cloudy. Moderate to strong west wind. Alpine temperature -10. Freezing level 1000 m.THURSDAY: Flurries, accumulation 5cm. Moderate west wind. Alpine temperature -10. Freezing level 1000 m.FRIDAY: Mainly cloudy. Moderate gusting to strong west wind. Alpine temperature --8. Freezing level 900 m.
Avalanche Summary
There have been no reports of avalanche activity in the region since last week's natural, wet cycle during the big rain event. To the north however, Kananaskis Country reports persistent slab activity to Size 2.5 initiating on layers at or near the base of the snowpack in the alpine and running to treeline. While natural avalanche activity has tapered off with a return to cooler temperatures and lower freezing levels, new snow and wind are creating wind slabs in alpine lee areas and the possibility of a slab release stepping down to a deeper layer within the snowpack still exists.
Snowpack Summary
As much as 10-15 cm of new snow has fallen on the most recent November rain crust at 2200 m and above while the valley bottoms saw rain. There is little information regarding snowpack structure however snowpack depths are believed to vary from 40-60 cm at 1800 m elevation, to 80-100 cm near 2300 m. Several crusts are suspected to exist within the snowpack including the most recent November crust down 10-15 cm. Below this crust lies the Halloween crust as well as the early October rain crust at the base of the snowpack.
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.
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.