Strong winds, heavy snowfall, and rising temperatures have resulted in HIGH avalanche danger.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Heavy snow and strong Southerly winds overnight and Friday morning. Freezing levels climbing up to about 1500 metres in the North and east of the region, and closer to 1800 metres in the Southwest of the region. Strong Southerly winds continuing on Friday and Saturday morning. Freezing levels dropping to 1400 metres on Saturday afternoon as the winds slow to moderate Southwest. Light Southerly winds combined with light precipitation and cooler temperatures on Sunday.
Avalanche Summary
There were a couple of size 1.0 storm slab avalanches on Wednesday that were triggered by skiers. The storm slab was reported to have settled into a more cohesive slab with the warming temperatures. Expect natural avalanche activity and avalanche size to increase with storm loading.
Snowpack Summary
The storm slab continues to develop and is 40-60 cm thick and sits on a variety of old surfaces including crusts, surface hoar, and old wind slabs. Ski penetration has been reported to be about 50 cm in the North of the region. A crust can be found below about 1900m in the north of the region and below 2200m in the south of the region. At higher elevations the new snow covers old wind slabs formed by moderate southwest winds. Several persistent week layers can be found deeper in the snowpack that may be capped by the overlying crust at lower elevations. The mid-January surface hoar is buried between 40 and 80cm down and remains a concern at treeline and above. The mid-December surface hoar layer is now 80 to 140cm below the surface and appears to be slowly gaining strength.
Problems
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.
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.