Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Initially, the approaching frontal system will spread light-moderate precipitation amounts with rising freezing levels. Towards the end of the forecast period a cooling, drying trend will take place before a big warm-up next week.Friday: Overcast with light- moderate precipitation amounts. Ridgetop winds will blow moderate from the SW and freezing levels will rise to 1900 m.Saturday: Overcast with moderate precipitation amounts. Ridgetop winds will blow moderate from the NW and freezing levels near 1400 m then falling to valley bottom overnight.Sunday: Mostly sunny skies with a cooling, drying trend. Freezing levels will rise to 1200 m by the afternoon.
Avalanche Summary
On Wednesday, a remotely triggered a size 2.5 slab avalanche from a North aspect at 2700 m occurred from the ridgetop. A large whumph was heard and felt with no involvements.
Snowpack Summary
Over the past 2 days, melt-freeze crusts have formed on solar aspects. North aspects remain dry, with new surface hoar development and surface faceting. Forecast snow and wind may build new wind slabs, burying older wind slab problems found at treeline and above. Cornices are very large and remain a concern.In some locations a surface hoar interface exists buried within the upper metre of the snowpack. This is mostly found on northerly aspects at upper elevations. It may be slowly gaining some strength, but I’d remain suspicious and practice caution around these slopes. On other aspects, the storm snow overlies a crust. This crust interface has recently become reactive in regions further south and may become reactive in your area with additional load.
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.