As the recent storm snow begins to consolidate into a slab, natural and human triggering becomes more likely. Select lower-angle terrain and avoid exposure to large paths and overhead hazards like cornices.
Problematic weak layers are becoming spotty across the region, however recent large persistent slab avalanche observations continue to trickle in reminding us that these layers remain a concern in this region. Recent avalanches have been triggered by a mix of large loads like cornices.
Up to 60 cm of new snow has accumulated over the past 36 to 48 hours developing storm and wind slabs that are building over various surfaces of surface hoar, wind-pressed and old wind slabs, soft snow in sheltered areas, and burying a thin melt-freeze crust on south aspects from sunny skies on Wednesday.
A layer of large and weak facets sits near the base of the snowpack. This layer continues on a sporadic basis to produce very large avalanches that can travel far. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer. Cornices will continue to grow with new snow and wind and could be the large load needed to trigger deep persistent weak layers. Your best defense is to stay diligent in choosing low-consequence terrain away from overhead exposure.
Several loose dry avalanches were reported with sluff management being a consideration throughout the day.
Touchy storm slabs up to size 1.5 were reported as snowfall accumulated through Thursday.
Looking forward storm snow will need some time to settle and stabilize and may be particularly touchy where new snow has buried a surface hoar layer that developed earlier in the week. Wind slabs will likely develop at upper elevations throughout the day as another system travels through the region bringing variable winds.
Another 10 to 15 cm of new snow overnight brings recent snowfall totals of 50 to 65 cm of low-density snow. New snow is forming storm slabs that may be more reactive where they have settled on a surface hoar layer that developed earlier this week.
Moderate variable winds throughout the day will be redistributing new snow into wind slabs at treeline and alpine elevations. Cornices continue to build new overhanging edges with this new snow and winds.
The mid-pack is generally well consolidated with a few operations reporting continued snowpack results on a spotty surface hoar layer down roughly 80 cm. Reports of large avalanches involving various layers of surface hoar/crusts and facets within the mid-pack depth are sporadic but are a reminder of the complicated snowpack across this region.
In the lower snowpack, a layer of large and weak facets from November near the base of the snowpack is slowly gaining strength but there continues to be low confidence in this layer. Large destructive avalanches are the result of this layer being triggered.
Friday night
Mainly cloudy with snowfall, 5 to 10 cm accumulation, 15 to 20 km/h southwest winds, treeline temperatures -8 °C.
Saturday
Mainly cloudy, flurries with 5 to 10 cm accumulation, 20 to 30 km/h west winds, treeline temperatures -7 °C.
Sunday
Cloudy with flurries, 15 to 20 cm accumulation, 15 to 20 km/h southwest winds, treeline temperatures -6 °C.
Monday
Cloudy with flurries, 5 to 10 cm accumulation, 15 to 20 km/h westerly winds, treeline temperatures -8 °C.
More details can be found in the Mountain Weather Forecast.
