A size 2 avalanche occurred yesterday on the middle pitches of a popular ice climb indicating that slabs are loaded in gully features. Pay attention when moving between pitches on ice climbs.
Weather Forecast
A front will be coming through sometime between Friday night and Sunday morning with strong Westerly winds and snow flurries. Warmer temperatures are expected in valley bottoms and may be acompanied by some rain. Snow flurries may accumulate to between 10 -20cm for the weekend, while the valley bottoms will see only dustings.
Snowpack Summary
Variable wind slab on lee features at treeline and alpine elevations. Variable snowpack depths, particularly in the alpine, with pockets up to 1m deep. October's rain crust is sporadically distributed but forecasters are still investigating this condition. Last weeks North winds have loaded slab snow onto South aspects.
Avalanche Summary
Friday's patrol on Highway 93 resulted in no new avalanches observed. However a report from climbers indicated a size 2 slab release on Thursday morning on the middle pitches of polar circus which is a popular ice climb in the area. Strong wind gusts were evident on the climb at the time of the slide indicating snow loading in the gully.
Confidence
Timing of incoming weather systems is uncertain on Saturday
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.