Conditions are variable across the region. Cautious route-finding and conservative decision-making are essential.
Confidence
Fair - Wind effect is extremely variable
Weather Forecast
Snowfall is expected to increase overnight and into Friday (5-10 cm by Friday afternoon). Winds are forecast to be moderate from the SW to NW. Freezing level at valley bottom. Snowfall becomes light on Saturday before a second pulse of snow arrives late on Sunday.
Avalanche Summary
Explosives control on Tuesday produced several avalanches up to size 3. Some of these failed on persistent weak layers, while others only involved surface snow. Natural wind slabs were also observed near ridge tops over the last couple of days.
Snowpack Summary
Variable wind slabs exist in some areas. A spotty thin layer of surface hoar was buried on December 27th by about 5-10 cm of light dry snow. As more snow accumulates, this interface could become one to watch. A persistent surface hoar/crust weak layer from mid-December is now down about 40-60cm. Recent snowpack tests show moderate pops-type results here, indicating the potential for avalanches to propagate on this layer. This persistent slab problem is reasonably widespread across the region and is not expected to improve quickly. A deeper crust/facet layer which formed early in the season may still be triggerable from thin or rocky snowpack areas.
Problems
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.
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.