Winds will be cranking through the weekend! New wind slabs may be easily triggered by a skier or snowmobiler.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The dominating Arctic high slides south allowing a series of Pacific frontal systems to cross the Interior through the forecast period. Strong ridgetop winds will crank up Saturday accompanied by new snow and slightly warmer temperatures Sunday and onward.Saturday: Cloudy, alpine temperatures -16, ridgetop winds from the West 30-60 km/hr, snow 5 cm. Sunday: Cloudy, alpine temperatures -12, ridgetop winds SW 50-60 km/h, snow 5-10 cm.Monday: Cloudy, alpine temperatures -8, ridgetop winds SW 40-80 km/h, snow 15-20 cm.
Avalanche Summary
Recent avalanche observations include a natural cornice fall up to size 1.5, not triggering a slab on the slope below and loose dry sluffing up to size 1.5 from steeper terrain features. On Wednesday, a recent glide crack released up to size 3 from steep south facing terrain around 2500 m. Strong winds over the weekend will likely build new wind slab problems that may be easily triggered by light loads like a skier or snowmobiler.
Snowpack Summary
Recent wind has formed isolated wind slabs on a variety of aspects in the alpine. The surface snow has been faceting due to the cold temperatures, and some surface hoar has been developing in sheltered locations. The mid-pack has been reported to be well settled above a crust that was buried in mid-November. This crust is be buried 90-160cm deep, depending on elevation and previous exposure to winds. Snowpack tests on the crust have shown variable results from sudden to no result. If you dig down to the crust, watch for facets (sugary crystals) developing above and below. This may provide a hard surface with a weak sliding layer in the future.
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.