Wind slabs may linger with the cold temperature. If triggered, they have the potential to step down to a buried weak layer.
Weather Forecast
SUNDAY NIGHT: Cloudy with light snowfall, accumulation trace to 5 cm, alpine temperature -24 C.MONDAY: Cloudy with light snowfall and afternoon clearing, accumulation trace to 5 cm, light northeast wind, alpine temperature -20 C.TUESDAY: Mostly cloudy with intermittent snowfall, light north wind, alpine temperature -20 C.WEDNESDAY: Partly cloudy, light west wind, alpine temperature -18 C.
Avalanche Summary
Many large storm slab avalanches were triggered naturally, by skiers, and by explosives on Saturday. The avalanches likely released at the base of the storm snow as well as within the weak layer of surface hoar buried mid-January described in the Snowpack Summary.
Snowpack Summary
Around 60 mm of precipitation fell on Friday with a freezing level at 1600 m. Above 1600 m, the precipitation fell as snow, which has been redistributed by northwest winds. It may sit on weak and feathery surface hoar crystals in shaded and sheltered areas. Below 1600 m, the precipitation fell as rain and froze into a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 40 to 60 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m. The melt-freeze crust is found on south aspects at all elevations.The remainder of the snowpack is generally well-settled. Thin snowpack areas, such as in the east of the region, may find weak and sugary faceted grains near the base of the snowpack.
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.
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.