Regions
Northwest Inland.
A few days of cool benign weather. Concerns include wind slabs at higher elevations and the ongoing potential to trigger deep persistent slabs in shallow snowpack areas.
Confidence
High - The weather pattern is stable
Weather Forecast
SUNDAY: Cloudy with sunny periods, light south winds, alpine temperatures around -17 C.MONDAY: Cloudy with isolated flurries and trave amounts of new snow, moderate south winds, alpine temperatures around -15 C.TUESDAY: Scattered flurries with 5-10 cm of new snow, moderate south winds, alpine temperatures around -15 C.
Avalanche Summary
On Friday, several size 1-2 natural wind slabs were reported in both the Telkwas and Sinclair areas on north and east aspects. The avalanches likely occurred during the storm on Thursday. A few small size 1 slab and loose dry avalanches running on a crust were skier triggered in steep low elevation terrain. Isolated wind slabs may still be found in alpine locations on leeward slopes behind terrain features.
Snowpack Summary
Recent low density storm snow up to 25 cm has fallen with some wind effect at higher elevations. The new snow buried a variety of old snow surfaces including stiff wind slabs, facets, crusts and surface hoar. The new snow may have a poor bond to these interfaces, especially in places where the slab is stiffer and more cohesive due to winds. At treeline elevations the average snowpack depths are 120-190 cm and a well consolidated mid-pack of approximately up to 100 cm sits above weak basal facets (sugary snow) near the ground. Recent snowpack testing has shown sudden easy results down 25 cm on a surface hoar layer and sudden hard results down 100 cm within the faceted snow. The deeper basal weakness remain a concern, especially in thin rocky start zones and shallow snowpack locations.
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.