Conditions have shifted towards a period of more conservative decision making in the backcountry. The latest surface hoar layer to be buried is the largest yet and will be most reactive as the slab overtop continues to build strength.
Weather Forecast
Snow easing off this morning, flurries forecast for the rest of the day with mild temperatures and mountain top winds northwest 30-50km/h. Unsettled conditions will persist with light snow as a weak ridge of high pressure slowly builds until a Pacific system arrives Tuesday night.
Snowpack Summary
20-30cm of recent snow has buried large surface hoar which sits on a rain crust to 2100m and on settled snow above 2100m. Settlement and winds that have just started to ramp up are likely to make the slab more sensitive higher up. Mid-pack is well settled with Nov 9 crust/facet layer in the bottom 30cm.
Avalanche Summary
A backcountry report of a skier triggered size 1.5 avalanche,10-15m wide, 10-15cm deep, from Balu Pass, northeast aspect, at ~2000m on a convex roll just below the ridge. 6 size 2.0 natural slab avalanches observed yesterday east of the Rogers Pass summit in the highway corridor.
Confidence
Due to the number of field observations
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.