Anticipated warm weather at high elevations will elevate avalanche danger on Saturday.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
FRIDAY NIGHT: A few flurries possible. Expected to stay cool overnight.SATURDAY: Dry. Temperatures warming gradually and a weak above-freezing level layer developing from approximately 1900-2300 m. Winds light northwesterly.SUNDAY: Light snow or rain (4-6 cm at higher elevations). Cooling rapidly through the day. Strong westerly winds.MONDAY: Dry. Freezing level at valley bottom. Light northwesterly winds.
Avalanche Summary
On Tuesday, Wedensday and Thursday, several storm slabs and persistent slabs avalanches up to size 2 were triggered by people on the recent weak layer buried approximately 30 cm below the surface. The majority of these avalanches occurred at treeline and below, however, there have been a few noted at higher elevations in the alpine. Wind slabs avalanches have been triggered remotely on east and northeast slopes.
Snowpack Summary
20-35 cm of snow sits above a layer of large surface hoar crystals and sun crust. In areas that have had wind effect the recent snow has been settling into a thin but reactive slab above this weak layer, with enhanced reactivity noted at elevations between 1500-1800 metres. In sheltered areas the snow lacks cohesion above this layer and is only reactive as dry loose sluffing. Warmer temperatures are consolidating the upper snowpack are will likely make slab avalanches more widely triggerable.The middle and lower portions of the snowpack are generally well-settled and strong.
Problems
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.