New snow, strong winds and rising temperatures make a good recipe for rising avalanche danger over the next few days.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
Expect light to locally moderate snow from Saturday to Monday. Temperatures rise towards 0 at 1500m by Saturday. Winds are expected to be moderate to strong from the west to south-west throughout the period.
Avalanche Summary
On Thursday and Friday, explosive control produced several size 1-2 slabs. These slabs were around 20cm thick. In the Dogtooth area, these failed on reloaded bed surfaces (early November rain crust/facet layer). A size 2.5 naturally-triggered slab was observed at 2600m on an east aspect on Friday.
Snowpack Summary
New snow sits on variable surfaces including wind-affected snow, surface hoar and a crust which exists below about 2200m. Winds are expected to shift new snow onto lee slopes over the next couple of days. A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas. A weak layer from the end of November sits in the middle of the snowpack and is still reactive in some 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.
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.