Rising temp's and strong winds are promoting wind slab development. These slabs are likely to be triggered by human loads. Stick to conservative, supported terrain.
Weather Forecast
Today will bring rising freezing levels (1600m) and moderate to strong SW winds. A pulse of snow should arrive tonight, bringing 10cm. Monday should be slightly cooler with flurries, but winds will increase to strong from the SW. More snow on Tuesday; 25cm with strong SW winds and freezing levels rising to 1400m.
Snowpack Summary
Extreme S winds on Saturday morning created wind slabs in the alpine. The December 9th persistent weak layer (surface hoar, sun crust and facets) is buried 60-100cm and is reactive where the overlying slab is dense. The November 21st persistent weak layer is down 120-160cm. Height of snow at treeline is approx 2m, and 1m at Rogers Pass.
Avalanche Summary
An extensive natural avalanche cycle occurred early Saturday morning, correlating with the high to extreme winds measured at that time. Numerous avalanches from sz 2 to 3's were observed both east and west of the summit from all aspects. A skier-triggered sz 1.5 avalanche off a gully sidewall partially buried one person in NRC Gully Saturday.
Confidence
Due to the number and quality of field observations
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.