New wind slabs are expected to build on Sunday in exposed areas at upper elevations. Continually assess local conditions as you travel and use extra caution as you transition into wind affected terrain.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A weak storm system will result in snowfall Saturday night and Sunday. 5-15cm of new snow is expected with the largest amounts towards the north of the region. Alpine winds are expected to be moderate to strong from the SW and treeline temperatures should be around -10C. On Monday, unsettled conditions are expected as the storm exits the region. Light intermittent snowfall is possible in the morning and sunny breaks are possible in the afternoon. Alpine winds should ease to light after the storm passes and treeline temperatures should remain around -10C. On Tuesday, a ridge of high pressure builds and sunny conditions are expected.
Avalanche Summary
Some small natural wind slabs were reported on northern aspects in the alpine on Wednesday. On Thursday, explosives were used in the north of the region but only triggered loose sluffing from steep slopes on a variety of aspects. On Friday, ski cutting of steep convex features in the alpine produced two size 1 loose dry avalanches. New wind slabs are expected to form during the weekend storm and may be sensitive to human-triggering on Sunday.
Snowpack Summary
30-50cm of low-density snow typically overlies a well-settled mid and lower snowpack. New wind slabs are expected to form this weekend as winds increase with the storm system. Between 80 and 130cm below the surface you'll likely find a weak layer which was buried in early December. Between 1400m and 1800m, this layer consists primarily of large surface hoar. At higher elevations, this layer consists of a sun crust, facets, and/or small surface hoar. Field reports indicate that human-triggering of this layer has become unlikely but heavy triggers such as a cornice falling or smaller avalanche may still have the potential to step-down. Below this layer, the snowpack is thought to be generally strong and well-settled.
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.