Snowfall amounts for Friday are uncertain, exercise extra caution if forecast accumulations are exceeded.
Weather Forecast
Friday: Snowfall (10-15cm) in the AM (clearing trend in the PM). Ridgetop wind moderate N (trending light). Treeline temps, High -2, Low -6.Saturday: Partly cloudy, PM flurries. Ridgetop wind strong SW. Treeline temps, High -1, Low -4.Sunday: Parlty cloudy, AM flurries. Ridgetop wind mod-strong SW. Treeline temps, High -7, Low -10.
Snowpack Summary
Fresh storm slabs will form Friday with incoming snow and N winds. These will likely be touchy as they will overlie; a thin melt-freeze crust on all but north aspects above 2000m, scoured old crust in wind exposed terrain, and wind slab 10-40cm deep on N aspects. Treeline and above, the basal snowpack remains faceted and weak in many locations.
Avalanche Summary
A few small-large (up to size 2.0) wind slabs were observed on alpine N aspects Thursday. Several large to very large avalanches from last week and the week before suggest that deep persistent weaknesses in the snowpack will remain as a concern well in to the spring.
Confidence
Forecast snowfall amounts are uncertain
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.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.