Cold north winds have been blowing. Watch for fresh wind slabs, particularly on southerly aspects.
Weather Forecast
MONDAY: Dry and sunny. Winds northeasterly 20-30 km/h at ridgetop. Ridgetop temperatures around -15C. TUESDAY: Dry and sunny. Winds northeasterly 20-30 km/h. Temperatures around -16C. WEDNESDAY: Dry and sunny. Winds northeasterly 40-60 km/h. Temperatures around -12C.
Avalanche Summary
Small wind slab avalanches could be triggered in recently loaded pockets up to size 1.
Snowpack Summary
The critical part of snowpack analysis under current conditions is figuring out how the wind is redistributing snow into wind slabs. Extreme northerly winds have been reported, which will be "reverse loading" wind onto slopes that were previously scoured. I suspect the cold will temper the reactivity of wind slabs on moderate slopes; however, on steep, aggressive terrain, particularly on south-facing slopes in the sun, wind slabs will definitely be in play. Between Monday and Friday last week, 70-100 cm of storm snow accumulated in the region. Below the new snow from this week lies the Boxing Day interface which consisted of wind affected surfaces, faceted (sugary) snow, or surface hoar. Recent observations suggest the overlying snow is generally well bonded to this interface. The mid-December interface is now down 100-150 cm and is generally considered to be stable in this region. Snowpack layers below this are well bonded.
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.