Snow, wind and warming are a recipe for elevated danger. Storm and wind slabs will be touchy at treeline and above. Avoid overhead hazard: Conservative terrain use is essential this week!
Confidence
Low - Intensity of incoming weather systems is uncertain
Weather Forecast
We'll have moderate snowfall amounts through to Monday afternoon, and then it starts to warm up.MONDAY: Cloudy with another 15-20cm by late afternoon accompanied by moderate to strong SW winds and freezing levels rising as high as 1500m.TUESDAY: Scattered flurries (3-5cm) with moderate southerly winds. Freezing levels remain near 1600m.WEDNESDAY: Cloudy with another 10-20cm of fresh snow throughout the day accompanied by moderate SW winds. Alpine temperatures hovering around -2 C.
Avalanche Summary
On Sunday we had reports of a widespread natural avalanche cycle up to Size 3 on all aspects and elevations at treeline and in the alpine.
Snowpack Summary
Around 40-60cm of fresh snow has fallen over the past three days (with light to moderate southerly winds) and has added to the 50-100cm of settled storm snow from the past week. Touchy storm slabs can be found at all elevations with weaknesses within and under this recent snow.All this new snow is bonding slowly to faceted snow as well as isolated small surface hoar in sheltered areas and a thin sun crust on steep southerly aspects.The persistent weakness buried mid-February is now down 80-140 cm, and is composed of a thick rain crust as high as about 1800 m, sun crusts on steep southerly aspects, and spotty surface hoar on shaded aspects. Recent reports show the bond to this interface becoming more variable.The mid and lower snowpack are well settled and stable in deeper snowpack areas, but may be weak and faceted in shallow areas.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.