Updated on Thursday at 6:45 AM Pacific: New snow and wind is creating very dangerous conditions in the alpine. Fresh storm slabs are building at all elevations and will likely increase in reactivity as it continues to snow and blow through the day. A small avalanche could step down to deeper weak layers.
New snow and strong wind will likely build reactive storm slabs through the forecast period. Storm and wind slab avalanches may step-down to deeper weak layers initiating large and destructive avalanches.
A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and lower alpine elevations. 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.
No new avalanches were reported on Tuesday.
Many wind slab avalanches were triggered by riders and naturally last Saturday. They occurred on all aspects.
Looking forward, natural and rider-triggered storm and wind slab avalanches are likely as we receive new snow and strong wind through the forecast period. Smaller avalanches could step down to the facets near the base of the snowpack, producing very large avalanches. See more on the potential of triggering deeper weak layers Forecasters' Blog.
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Up to 20 cm of fresh low-density snow may form new storm slabs and wind slabs in leeward terrain features. The snow will rest on previously wind-affected snow. Below this, a melt-freeze crust is found on sun-exposed slopes and everywhere below 1600 m.
Several crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack. Recent observations suggest these layers are not as concerning as in neighbouring regions.
The most concerning layer is at the base of the snowpack from large and weak facets formed in November. This layer is widespread and most likely problematic in steep, rocky alpine terrain.
Wednesday Night
Cloudy new snow 5-10 cm. Ridgetop wind 20-40 km/h from the west. Treeline temperatures steady -12 °C.
Thursday
Cloudy with snowfall, accumulation 10-20 cm by late afternoon with local enhancements possible. Ridgetop wind 30-50 km/h from the west and treeline temperature -10 °C.
FridayCloudy with snowfall, accumulation 10-20 cm. Ridgetop wind 40-60 km/ h from the west. Treeline temperature -6 °C.
SaturdayCloudy with snowfall, accumulation 5 to 10 cm. Ridgetop wind 30-40 km/h from the southwest and treeline temperatures warming to -5 °C. Freezing level 1000 m.
More details can be found in the Mountain Weather Forecast.
