Watch for bouts of sunshine to destabilize the new snow. Natural cornice falls triggering slabs have been a regular occurrence recently.
Weather Forecast
Wednesday: A mix of sun and cloud. Moderate west winds. Freezing level to 1500 metres with alpine high temperatures around -4.Thursday: A mix of sun and cloud. Light west winds. Freezing level to 1600 metres with alpine high temperatures around -3.Friday: Mainly cloudy with isolated flurries and a trace of new snow.Moderate to strong west winds. Freezing level to 1300 metres with alpine high temperatures around -3.
Avalanche Summary
Three more natural cornice releases were observed triggering size 2 storm slabs in the Fernie area on Monday.Reports from Sunday included numerous observations of recent large (size 2-2.5) natural storm slab releases in the Fernie area. Another round of explosives control yielded similar results, with slab depths generally from 30-70 cm. All but southwest aspects showed activity above 1800 metres and northeast aspects were the most active. Two natural cornice releases were also observed triggering slabs on the slopes they landed on.Cornice control on Saturday work gave numerous size 1-2 avalanches on north through southeast ridgelines. above 1900m. The cornice failures produced mostly loose dry avalanches from the slopes below with a few smaller slabs only releasing in the storm snow. On Friday, numerous natural storm slab avalanches were reported from north aspects above 1700 m.
Snowpack Summary
Up to 50 cm of recent storm snow has been showing a poor bond to the old snow surfaces it has buried, including a melt-freeze crust on sunny aspects and all aspects below 1600 m as well as surface hoar on north aspects above 1600 m. Wind slabs are building on most aspects due to the changing winds and overhanging cornices exist along ridgelines. Natural cornice falls triggering large avalanches has been a trend for the past few days.Deeper in the snowpack, the mid-December and late-November weak layers are composed of crusts and sugary facets, which are down 150-300 cm. These layers are currently considered dormant.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.