Snow, wind and warming will keep storm slabs touchy. When you add the prospect of cornice triggers, the likelihood of large persistent slabs is expected to increase.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
We'll have light to moderate snowfall amounts through to Monday morning, and then it starts to warm up Monday afternoon. SUNDAY: Cloudy with another 10-15cm of fresh snow by morning and continued light flurries throughout the day accompanied by moderate SW winds. Alpine temperatures hovering around -5 C.MONDAY: Cloudy with another 5-10cm by morning accompanied by moderate to strong SW winds and freezing levels rising as high as 1800m.TUESDAY: Scattered flurries (3-5cm) with moderate southerly winds. Freezing levels remain near 1900m.
Avalanche Summary
A widespread wind and storm slab avalanche cycle to Size 2.5 was reported on Friday at all elevations and aspects, particularly in the alpine.
Snowpack Summary
Around 25-40cm of fresh snow has fallen over the past two days (with moderate southerly winds) and has added to the 60-100cm 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 90-135 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. This and deeper persistent weaknesses have seen a recent increase in more sudden snowpack test results and has been identified as a failure plane in a number of recent avalanches.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.