Visible patterns of wind loading will help you to navigate around unstable pockets of wind slab. A less obvious persistent slab problem should have you raising your guard at mid elevations.
Weather Forecast
Wednesday night: Clear with cloudy periods. Light west winds.Thursday: A mix of sun and cloud with isolated flurries and a trace of new snow, continuing overnight. Light to moderate southwest winds, increasing to strong northwest in the aline. Alpine high temperatures around -16.Friday: Cloudy with scattered flurries bringing up to 5 cm of low density new snow, continuing overnight. Light northeast winds. Alpine high temperatures around -21 and cooling over the day.Saturday: Mainly cloudy with easing flurries finishing with around 2 cm of new snow, bringing new snow totals to about 10 cm. Light northeast winds, with strong southeast winds in the alpine easing over the day. Alpine high temperatures around -24.
Avalanche Summary
No new avalanches were reported on Sunday. One observation of an older natural size 2 wind slab release was reported from the Castle area on Tuesday.Many small to large avalanches were triggered within the recent storm snow by skiers, naturally, and with explosives on Saturday. The fact that we have numerous weak layers within our snowpack indicates that conservative decisions should be made at this time.
Snowpack Summary
Above 1700 m, 25 to 35 cm of recent snow overlies a variety of surfaces, including feathery surface hoar crystals in shaded and sheltered areas, wind-affected snow in exposed terrain, and a melt-freeze crust on southerly aspects. Below 1700 m, expect to find around 5-10 cm of low-density snow on a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 35 to 45 cm deep. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2100 m. The melt-freeze crust is found on south aspects at all elevations.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.