Regions
South Coast Inland.
The incoming storm will form new wind slabs and increase the avalanche danger at higher elevations. If the southern portion (Coquihalla) sees more than 25cm, the danger rating will be CONSIDERABLE.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
SUNDAY: Flurries starting in the afternoon, moderate southeast winds increasing throughout the day, alpine temperatures around -10. MONDAY: 5-15 cm of new snow in the north (Duffey Lk road) and 25-30 cm in the south (Coquihalla). Snow continuing with an additional 10-15 cm possible in the south. Moderate south west winds with strong gusts, alpine temperatures around -5. TUESDAY: Clearing in the morning, light northerly winds, alpine temperatures around -12. WEDNESDAY: Sunny with light northerly winds, alpine temperatures around -14.
Avalanche Summary
No new avalanches observed this weekend. Wind slabs were reactive in the Duffey Lake area earlier in the week, including an avalanche involvement reported on the MIN and an explosive triggered wind slab. Be on the lookout for wind loaded pockets where reactive wind slabs may still be lingering.
Snowpack Summary
Up to 5 cm of snow from Friday covers a variable surface with a mix of soft wind slabs, hard wind slabs, sastrugi, faceted snow, sun crust, and even some surface hoar. Last week's winds were primarily from the north, which reverse loaded many terrain features and formed stubborn wind slabs. For low snow areas, such as the northern part of the region, two layers of concern exist. One is a weak layer of snow from mid-December buried approximately 50 cm deep and other is an old rain crust from November buried 80-120 cm deep. Snowpack tests indicate these layers may be possible to trigger in shallow snowpack areas. Elsewhere, these layers are typically much deeper and are considered to be stable.
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.
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.