New snow may take some time to stabilise. Sunny periods may weaken the slab where it is sitting on a buried crust.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Thursday
Weather Forecast
Overnight and Thursday: Becoming overcast this evening with a chance of some convective flurries. Light Easterly winds overnight and during the day. Freezing levels dropping down to 600 metres overnight and rising up to 1300 metres during the day. Some chance of sunny periods in the afternoon.Friday: Overcast with snow starting in the morning and becoming heavy snow fall in the afternoon. Building Southwest winds becoming strong by the afternoon. Freezing levels rising up to about 1500 metres.Saturday: Snow and Southwest wind continuing. Freezing level rising to about 1700 metres.
Avalanche Summary
Reports of widespread natural avalanche activity in the top 20-30 cm of new snow up to size 2.0. Explosives control resulted in storm slab releases up to size 2.5 that were 50 cm deep. One explosive controlled cornice was reported to have released size 3.0. Some moist loose size 1.0 avalanches due to solar exposure. The new snow may take a couple of days to settle and bond.
Snowpack Summary
30-50 cm of new snow overnight that started warm and finished cold. The new snow is sitting on a mix of thin wind slabs and melt-freeze crusts on solar aspects and may not be well bonded to these old surfaces. This new snow combined with recent storm snow is sitting on a mix of facets and surface hoar on shaded aspects. The added load of storm snow or storm slab avalanches in motion may trigger the March persistent weak layer. The early-March crust/facet layer is down about 100-150 cm and the early February layer is now down close to 200 cm.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.