Lingering weak layers will become more reactive with the incoming storm. Be prepared to back off to mellow terrain if you see signs of wind loading.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
TUESDAY: Flurries with accumulations of 5-15 cm, strong west winds, alpine temperatures around -8C.WEDNESDAY: Cloudy with isolated flurries, strong west winds, alpine temperatures around -10C.THURSDAY: Cloudy with isolated flurries, strong to extreme west winds, alpine temperatures around -10C.
Avalanche Summary
Avalanche reports over the weekend were limited to small loose dry avalanches triggered by ski cutting and a natural size 1.5 cornice fall. On Friday, skiers in Kananaskis Country remotely triggered a size 2 avalanche from 35 m away on a wind slab over a weak layer of facets, which resembles snowpack conditions in the South Rockies.Fresh wind slabs will be the primary concern on Tuesday, with the incoming storm bringing new snow and strong winds. However, larger avalanches releasing on deeper persistent weak layers remain possible to trigger, particularly in previously wind-affected terrain. In the southeast corner of the region, recent explosive results suggest there are also weak facets near the ground that may be possible to trigger from thinner snowpack areas.
Snowpack Summary
Expect another 5-15 cm of new snow by Tuesday afternoon. Strong west winds will redistributed low density snow and form touchy wind slabs in the lee of ridgetops. A variable interface that formed during the cold snap in early December can be found buried 30-50 cm deep. This interface consists of weak faceted (sugary) snow and preserved surface hoar in sheltered areas. The interface is likely most reactive in wind-affected terrain where it is covered by hard wind slabs. The snowpack is a generally weak and faceted below this interface, including another weak layer with surface hoar or facets that was buried in early December. Below treeline, the snowpack is very shallow and early season hazards such as stumps, rocks, and open creeks are still a major concern.
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.