Expect to continue to see persistent slab avalanche activity as the snow sitting above the persistent weak layer further settles and consolidates with forecast warmer temperatures. Adopt a conservative approach in the coming days.
Confidence
Moderate - Freezing levels are uncertain on Friday
Weather Forecast
FRIDAY: Cloudy with isolated flurries, accumulation 3-5cm / Light southwest wind / Alpine temperature -3 SATURDAY: Cloudy with isolated flurries and sunny breaks / Light to moderate southwest wind / Alpine temperature -4 SUNDAY: Cloudy with flurries / Light to moderate west wind / Alpine temperature -5
Avalanche Summary
On Thursday there was a report of skier triggered avalanche in Orca bowl involving a group of 11 with 6 people caught and partially buried. This was a size 2 avalanche occurring on a northeast aspect at 1975m and reportedly running as a windslab sitting on a crust. Additionally there have been several natural avalanches between 1600m and 1800m on steep or open glades on all aspects. This is where the mid-December layer has been most active.
Snowpack Summary
A persistent weak layer buried mid-December is buried 40-70 cm below the surface. This layer can be found in a variety of locations, but most commonly can be found between 1600m and 1800m and consists of crusts on south and west facing slopes and feathery surface hoar in sheltered areas at and below tree line. It has been producing sudden results in recent snowpack tests.At higher elevations, wind has modified the snow pack creating a stiffer snow on top of softer snow condition. The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November. This crust has been reported to be unreactive, however it is possible that it may have been the bed surface for a skier triggered avalanche that happened on Thursday (See Avalanche Activity section below for details).
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.