Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Wednesday will see mostly cloudy skies with moderate snowfall occurring throughout Thursday and Friday. Winds will be moderate to strong from the west on Wednesday switching to strong and southwesterly for Thursday and Friday. Freezing levels should remain at about 1200m for the forecast period.
Avalanche Summary
Reported avalanche activity has been limited to size 1 and 2 loose snow avalanches out of steep, sun-exposed terrain.
Snowpack Summary
Snow accumulations from last week varied from 25-50 cm, although the resulting storm/wind slabs have most likely gained considerable strength with the more recent break in the weather.A buried surface hoar layer has been reported. Although I am unsure of its distribution throughout the region, the average depth is about 70 cm from the surface and seems to exist in specific, sheltered locations. Below this (down 80-110 cm) sits the early November crust. Test results on this layer have been variable; however, some have shown sudden planar pops on facetted crystals at this crust interface, or within the crust sandwich.Now is the time to take stock of what surface conditions may be developing in your area (surface hoar, sun crusts on steep solar aspects). Consider how these conditions will affect the snowpack once new snow arrives over the next few days.The snowpack depth in the alpine ranges from 130-225 cm. Treeline near 150 cm. A sharp transition exists below treeline, where the snowpack peters out around 1300 m.
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.