Confidence
Fair - Timing of incoming weather systems is uncertain
Weather Forecast
A ridge of high pressure will set up over the Interior regions bringing a dry, cool northwest flow Tuesday-Wednesday. The next system should arrive Wednesday night bringing snow, wind and warming. Generally, the pattern is repeating itself. Tuesday: Cloudy. Alpine temperatures -8. Ridgetop winds moderate gusting strong from the West.Wednesday: Snow amounts up to 20 cm. Alpine temperatures -8. Ridgetop winds moderate-strong from the West. Thursday: Cloudy. Snow amounts 10 cm. Alpine temperatures -5. Ridgetop winds light from the South. Freezing levels rising to 1100 m.
Avalanche Summary
Numerous loose dry avalanches up to size 2 were reported through the region.
Snowpack Summary
New snow (up to 40 cm in some places) has buried older wind slabs in exposed terrain at treeline and above. The new storm snow is settling quickly, however storm slabs have been touchy especially in wind affected areas. The average snowpack depths at treeline range from 100 cm -150 cm.Buried down 60 cm is a surface hoar, and facet layer. This layer has recently been reactive to riders and natural triggers and both cracking and whumpfing have been noted.Digging deeper down 70-90 cm is the late-November interface, which consists of a sun crust/ facet combo on steep south facing slopes and larger, proud surface hoar crystals in sheltered areas at lower elevations. This layer is generally considered to be "stubborn" to trigger. However, professionals are keeping a close eye on this layer. At the base of the snowpack the October crust is most predominant on north-facing alpine slopes with smooth ground cover. Triggering this weakness is unlikely, but if triggered the resulting avalanche would be very large and consequential.
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.