Heavy snowfall combined with strong westerly winds is expected to increase the avalanche danger.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A fast moving winter storm system is expected to bring heavy precipitation and strong winds to the region overnight. The storm may linger in the region for a couple of days. Winds should subside by the end of the forecast period. Cool temperatures should keep the freezing level at valley bottoms throughout the forecast period.
Avalanche Summary
New storm snow avalanches continue to be reported from all aspects and elevation bands in the region. Persistent slab avalanches have been observed on north and easterly aspects in the alpine and at treeline up to size 3.0. The ongoing storm is expected to increase the likelihood and size of avalanches over the next few days.
Snowpack Summary
A heavy load of new snow is expected to add to the existing storm snow problem. Additional loading above the persistent weak layer may result in continued easy triggering from light additional loads like skiers and riders. The weak layer of buried surface hoar crystals is now down about 100 cms in most parts of the region at treeline. In the alpine the weak layer may be down closer to 150 cms or deeper in wind loaded terrain features.
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.