A tricky snowpack is already taking shape in the Purcells. Continue to gather information as you travel and be sure to increase caution if you're venturing into the alpine.
Confidence
Low - Due to the number of field observations
Weather Forecast
Friday night: Mainly cloudy with light north winds.Saturday: Mainly cloudy. Light northwest winds. Alpine high temperatures around -8.Sunday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures warming to around -4.Monday: Mainly cloudy with scattered flurries bringing a trace to 10 cm of new snow. Light to moderate southwest winds. Alpine high temperatures of -2 as freezing levels rise to around 1500 metres.
Avalanche Summary
Skiers and explosives have recently triggered small wind slabs in cross-loaded and lee terrain features at treeline and alpine elevations. Earlier in the month, a natural avalanche cycle took place over the late October crust/facet combination. Be aware of the continued possibility for smaller avalanches to 'step down' or even initiate at this deeper layer.
Snowpack Summary
Light snowfall over Thursday and Friday buried a widespread layer of weak, feathery surface hoar crystals with about 5-10 cm of new snow. Reports from several points in the region show this surface hoar sitting above a layer of recently reactive wind slab that was created by strong winds earlier this week. This wind slab layer overlies yet another widespread layer of surface hoar from mid-November, now found about 20-40 cm deep. A final, prominent feature of the snowpack is a combination of a melt-freeze crust and underlying sugary, faceted snow found around the base of the snowpack. Avalanches have been triggered where there is a slab above this crust.
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.
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.