Solar radiation has lots of punch these days so when the sun does come out, stability will quickly deteriorate. Freezing levels on Thursday are forecast to be around 2100m.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain on Thursday
Weather Forecast
Cloudy with scattered flurries.Accumulation: 4 cm.Alpine temperature: High 0 °C.Ridge wind west: 30 km/h gusting to 85 km/h.Freezing level: 2100 metres.
Avalanche Summary
One new avalanche was observed today on an E aspect on Mt Murray. A sz 1 that was 80-100cm deep, about 50m wide and ran for around 150m. We suspect that a cornice collapse was the trigger.
Snowpack Summary
The alpine snow pack is complex due to variable wind direction and new snow over the past few days. Forecasters are not confident about stability in the alpine due to the variability of the snow depths. The concern is regarding triggering from a thin areas and wide propagations resulting in large avalanches. Some good skiing is found below 2300 meters in the trees although at lower elevations the snow pack is faceted and un supportive. Two main layers are important to note in the snowpack at this time. The Feb 11th interface down 30-50cm is producing moderate sheers but the quality of these sheers varies depending on aspect and weak layer, crust vs facets. The Jan 6th layer is down deeper 60-80cm and is producing more hard sheers but its likely that any avalanche initiating in the upper snowpack will step down to this interface. Dig down and evaluate these interfaces before committing to a feature.
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.