Wind, snow, and warm temperatures and forming fresh and reactive wind slabs in the alpine and treeline. Seek out sheltered areas where you can avoid wind slabs and find good riding.
Concern for buried weak layers warrants conservative terrain choices with an avoidance of steep and convex slopes.
Strong southerly wind and moderate snowfall will form wind slabs on north-facing terrain. While these new wind slabs will be the most likely to trigger, old thick wind slabs have been reported on a variety of aspects in alpine terrain.
Triggering persistent slab avalanches remains possible due to several weak layers in the top 30 to 80 cm of the snowpack. Facet layers are the primary concern in alpine terrain, while preserved surface hoar layers are the concern in treeline terrain. Recent observations suggest these layers are gradually strengthening, but are still on the radar of professionals.
As winds increased on Thursday, several natural and one human-triggered wind slabs (size 1-2) were observed in the alpine.
Triggering large persistent slab avalanches remains a concern. The most recent report of a persistent slab avalanche was from Monday when two size 2 persistent slabs were triggered on treeline features in northern parts of the region. These avalanches failed on 30 to 50 cm deep facet layers. Similar avalanches were reported in treeline terrain in southern parts of the region last week (Dec 29 and 30).
Strong to extreme wind is forming drifts and wind slabs in alpine terrain and along ridges. Recent storm snow continues to settle, with moist snow and crusts possibly forming on some surfaces. Several persistent weak layers may be found in the top meter of the snowpack, including a surface hoar layer buried on Dec 28 (30 to 50 cm deep) and a facet layer buried on Dec 23 (40 to 80 cm deep). These layers are increasing in strength, but could still be possible to trigger in specific areas. In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets, while in treeline terrain, they are most likely triggered on convex rolls in open trees where they present as preserved surface hoar.
Friday night
Cloudy with scattered flurries, 5-10 cm of accumulation. Alpine temperatures drop to a low of -1 °C. Ridge wind 20 km/h occasionally gusting to 60 km/h. Freezing level around 900 meters.
Saturday
Flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of 0 °C. Ridge wind southeast 30-70 km/h. Freezing level around 700 meters.
SundayA mix of sun and cloud. Alpine temperatures reach a high of -1 °C. Ridge wind east 10-20 km/h. Freezing level rises to 800 meters.
MondayA mix of sun and cloud. Alpine temperatures reach a high of -3 °C. Mostly light southeast ridge wind occasionally gusting to 30 km/h. Freezing level around 400 meters.
More details can be found in the Mountain Weather Forecast.
