Storm snow and moderate to strong S winds are forming fresh windslab, the avalanche danger is increasing.
Weather Forecast
10cm of snow expected today with an additional 20cm forecast to land by Saturday evening. Alpine winds SW 30km/h gusting to 80km/h today with S winds in the 25-45km/h range on Saturday. A soft slab forming forecast.
Snowpack Summary
From Bruins ridge at 2330m yesterday, East aspect we had a whole block RB 4 down 55cm about 5cm above the November crust. Also of interest was a 5cm graupel layer down 11cm giving sudden collapse results. The graupel layer may be sensitive today with the additional loading and soft slab formation from overnight storm snow and strong south winds.
Avalanche Summary
A natural avalanche cycle occurred overnight along the MacDonald avalanche paths up to size 3. Yesterday a size 2 avalanche was observed in Cheops 4 reaching the top of the fan. Southerly winds are increasing into the strong range this morning. Avalanche danger is increasing.
Confidence
Intensity of incoming weather systems is 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.
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.