Freezing levels and precipitation amounts are uncertain for Tuesday night. Watch for touchy wind slabs at higher elevations and stay aware of overhead hazards.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Wednesday
Weather Forecast
TUESDAY NIGHT: A short pulse of warm wet weather overnight will bring 10-15 mm of precipitation, strong southwest wind, and freezing level up to 2000 m.WENDESDAY: Cloudy with isolated flurries, strong southwest wins, freezing level dropping to around 1700 m.THURSDAY: Mix of sun and cloud, moderate southwest wind, freezing level around 1600 m with alpine temperatures around -5 C.FRIDAY: Increasing cloud, light wind, alpine temperatures around -1 C.
Avalanche Summary
A few small solar triggered avalanches were reported over the past few days, but there has not been any notable recent activity. A large avalanche cycle occurred during last weekend's storm, including some that stepped down to deeper weak layers well over a metre deep.New snow should form wind slabs at higher elevations, well warming and cornice falls are potential triggers for deep persistent slabs.
Snowpack Summary
Moderate amounts of alpine snow will form wind slabs at higher elevations on Tuesday night. Meanwhile at lower elevations, rain will once again soak the snowpack. A thick rain crust has formed near the surface at all elevations, but tends to break down with daytime warming at lower elevations and on solar aspects. Isolated basal facets exist in shallow snowpack areas and still have the potential to produce destructive full-depth avalanches.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.