Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Wednesday will see mostly cloudy skies with snowfall developing late in the day. Moderate snowfall will continue 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
A size 2 sled-triggered slab avalanche occurred on Sunday in the Yanks Peak area. It was on a northwest aspect at 1900m. For more details, check-out our Incident Data Base.
Snowpack Summary
Healthy amounts of snow fell throughout last week. Although alpine wind data has been sparse, velocities in neighboring regions were in the upper end of moderate during the storms. That said, I'd be highly curious about the possibility of windslabs in exposed areas. Although storm slab reactivity is still possible, a break in the snowfall over the last few days has most likely given the upper snowpack a chance to settle and gain some strength. There may be a thin buried surface hoar layer down about 85 cm in the alpine. As well, the November rain crust now exists over 100cm down in some locations and may exist in combination with facets. This layer has shown sudden planar test results.A you're traveling through the mountains, be on the look-out for current surface hoar development and think about how it will affect the snowpack as new snow arrives over the next few days.
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.