Avalanche danger will increase over the day as snowfall and strong winds layer new wind slabs over the surface at higher elevations. Watch for the destabilizing influence of the sun in the afternoon.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Friday night: Flurries bringing 5-10 cm of new snow. Moderate south winds, increasing to strong at ridgetop.Saturday: Cloudy with continuing flurries bringing 10-15 cm of new snow. Moderate to strong west winds. Freezing level to 1600 metres with alpine high temperatures around -4.Sunday: A mix of sun and cloud. Light northwest winds. Freezing level to 1700 metres with alpine temperatures around -3.Monday: Mainly sunny. Light southeast winds. Freezing level to 2200 metres with alpine high temperatures around 0 to +1.
Avalanche Summary
A few natural storm and wind slab releases were observed on Thursday, ranging from size 1-2.5. One of these was a size 2 slab triggered by a loose wet avalanche while the 2.5 wind slab was triggered by natural ice fall on a north aspect at 2200 metres. It featured a 45 cm crown fracture.Reports from Wednesday included an observation of a natural size 2 cornice release from a north aspect in the north of the region. Numerous natural loose wet avalanches were also observed on sun-exposed aspects in the Monashees.Tuesday's reports showed numerous small (size 1) storm slabs releasing both remotely and with ski cutting. Crown fractures were in the 35-40 cm range and activity was observed at all elevations and on all but west aspects.On Sunday, warm temperatures initiated widespread natural storm slab and loose wet avalanche activity on all aspects below 2300 m.In addition to heightened storm slab activity following regular snowfalls, observations from late last week also showed a pattern of heightened cornice failure activity.Looking forward, another round of snowfall is expected to introduce new surface instabilities over Friday night and Saturday.
Snowpack Summary
New snow is forecast to accumulate above a new melt freeze crust that can now be found on the surface on all but north aspects above about 2200 metres. Below it, About 70-100 cm of rapidly settling storm snow overlies another supportive crust which shares similar distribution to the surface crust.Within the upper snowpack there are now a few different crusts with the shallowest of these (down 30-50 cm) now a limited concern as warm temperatures have promoted settlement and bonding in the upper snowpack.With warm daytime temperatures and poor overnight recovery of cold temperatures, there remains some lingering concern around the mid-March persistent weak layer in the alpine where it is found 80 to 120 cm below the surface. This buried crust/surface hoar interface was widely reactive but is likely trending towards dormancy. It should be kept in the back of our minds for its capability to produce large avalanches should it be triggered with a heavy load such as a snowmobile or cornice collapse.Deeper persistent weak layers from December and January are considered dormant at this time.
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.