Weather Forecast
Saturday night: 5 - 10 cm Sunday: Moderate SW ridge top winds easing throughout the day. Isolated afternoon flurries. 1500m temp: -5 Freezing level: SurfaceMonday: Light S ridge top winds. 1500m temp -14 at day break, warming to -5 in the afternoon. No snow. Freezing Level: SurfaceTuesday: Light S ridge top winds. Treeline temp -6. No snow. Freezing Level: Surface
Avalanche Summary
We're starting to see the effect of the big winds midweek. More reports of large natural avalanches came in today. A few different operations reported naturally triggered slab avalanches to size 3, pulling out of N through E facing terrain in the alpine. Out of the wind, there's still some sluffing in the new snow too.
Snowpack Summary
An average of 150 cm of storm snow fell in the last 10 days across the region. Winds picked up Wednesday/Thursday of this week and wreaked havoc on wind exposed terrain both in the alpine and at the upper treeline elevations. Wind slabs and touchy cornices are now a serious concern on north through east facing slopes. Sluffing of the new snow is still a concern in steep wind sheltered terrain. There are some reports of a suncrust down around 100 cm in steep south facing features. The mid-pack is reported to be settling well. I haven't heard of any test results on the late November surface hoar in the last few days. The early November crust, near the base of the snowpack has also been inactive as of late. It's important to note that professionals are still cautious about these lingering persistent slab problems, but the likelihood of triggering is low. Be wary of steep complex terrain with a shallow snowpack, where triggering a persistent weakness is more likely.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.