The Special Avalanche Warning has been extended until January 4th. Stay vigilant and be cautious in your terrain selection. Touchy persistent slabs and wind slabs exist.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Arctic air dominates the province. The weather remains benign with cold and mostly clear skies through Wednesday. High level moisture is developing on Thursday bringing some cloud cover. Alpine temperatures will be steady near -15 accompanied by moderate NW winds. On Friday things begin to change, however; at this point confidence is poor in model solutions with precipitation amounts.
Avalanche Summary
On Monday, no new avalanches were reported in the South Rockies. However, wind slabs to size 2 were observed in the Lizard range. One was a natural avalanche and the other was skier controlled. With forecast northwest winds, we could see a new round of wind slab activity as surface snow gets redistributed onto south-facing slopes.
Snowpack Summary
Up to 30cm of low-density snow exists on the surface. In the alpine and at treeline, strong to locally extreme winds have transported this snow into stiff and reactive wind slabs in exposed lee areas. Up to 70 cm below the surface (more in wind affected areas) you may find a crust which formed in December. The crust, which may have surface hoar on top of it, may extend into the alpine to at least 2100 m. Where the crust exists, it may be bridging triggers from penetrating to deeper persistent weaknesses. However, on high alpine slopes above where the rain crust formed, or in areas where rain didn't occur, deeply buried facets may still be susceptible to triggering especially in thinner snowpack areas.
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.