The declining avalanche danger ratings depend on the cooler temperatures in this weekend's weather forecast. Danger ratings will rise on Monday with predicted rain and warming temperatures.
Weather Forecast
Temperatures will begin a slight cool down on Saturday. Moderate to strong ridge top winds will continue. Light precipitation can be expected with broken skies.
Snowpack Summary
Extreme NW winds have stripped alpine and tree line fetch zones. Hard to soft wind slabs are present on all lee slopes, predominately tree line and above. In thin areas, these slabs are sitting on weak basal facets. Below tree line, the old storm snow is moist and will consolidate with cooling temperatures, over a rotten base of facets.
Avalanche Summary
In the area around Whistler's, numerous full depth natural slab avalanches have been observed on thin, steep, lee slopes in the alpine. We are seeing wide propagation to size 3 from continued NW wind loading. These avalanches are running far in paths with steep run outs.
Confidence
Freezing levels are uncertain on Saturday
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.