Regions
Northwest Inland.
Cooling temperatures should help to stabilize the snowpack, but our lingering persistent slab problem can't be dismissed.
Weather Forecast
Friday: A mix of sun and cloud with thicker valley cloud due to lingering temperature inversion. Moderate to strong southwest winds. Freezing level dropping from 2500 to 2000 metres over the day.Saturday: Cloudy with scattered wet flurries bringing approximately 5 cm of new snow to higher elevations. Light rain below about 1500 metres. Strong southwest winds easing over the day. Freezing level to 2000 metres with alpine temperatures around 0.Sunday: Continuing wet flurries bringing a trace to 5 cm of new snow to high elevations. Light rain below about 1500 metres. Moderate south winds. Freezing level to 2000 metres with alpine temperatures around 0.
Avalanche Summary
No new avalanches have been reported, however it is expected that warm alpine temperatures and sunshine initiated natural activity on steep solar aspects at higher elevations on Thursday. Looking forward, we should see diminishing potential for natural activity until the next storm pulse brings new snow on Saturday.
Snowpack Summary
Average snowpack depths now total 80-140 cm at treeline elevations and up to 160 cm in the alpine. (Depths of up to 210 cm have been reported from the Howsons.) Solar and temperature crusts are expected to have formed on the wind-affected surface at higher elevations on Thursday. Below the surface, Approximately 30-50 cm of storm snow now overlies two crusts that were buried near the end of November. These crusts are widespread and extend into the alpine. Although snowpack tests have previously shown hard results at these crust interfaces, more recent observations have been limited. Below these crusts, a well settled midpack overlies the late October crust near the base of the snowpack. This "crust/facet combo" is widespread and has been reactive to rider and remote triggers and has produced recent sudden snowpack test results.
Problems
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.
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.