Regions
South Coast Inland.
Heavy snowfall in the southern part of the region on Friday will make conditions more dangerous than in the north.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Friday
Weather Forecast
FRIDAY: Flurries easing throughout the day with 10-20 cm of new snow in the south and trace amounts in the north, moderate west wind, alpine high temperatures around -6 C in the north and -3 C in the south.SATURDAY: Moderate snowfall with 10 cm throughout the day in the north and 30 cm in the south, strong southwest wind, alpine high temperatures around -6 C in the north and -2 C in the south.SUNDAY: Clearing and cooling with strong northeast wind and alpine high temperatures around -18 C in the north and -8 in the south.
Avalanche Summary
No new avalanches were reported on Thursday. On Wednesday, several size 2 wind slabs (40 cm thick) were triggered with explosives on south-facing slopes in the Duffey area. Wind slab activity has been reported in the northern part of the region over the past week, including some small (size 1) skier triggered slabs and some larger (size 2-3) naturally triggered slabs on a range of aspects in alpine terrain (some of which were triggered by cornices).Expect the incoming snow to form fresh slabs, particularly in wind-affected terrain.
Snowpack Summary
Southern parts of the region are expecting heavy snowfall on Friday and Saturday, likely forming fresh storm slabs as snow accumulates. Northern parts of the region are getting lighter amounts, so fresh slab development will primarily occur in wind-affected terrain.A few interfaces buried 10-20 cm below the most recent snow could potentially support wide propagations in the fresh storm/wind slabs. These include scoured crusty surfaces on south-facing alpine slopes, a melt-freeze crust up to about 1900 m, and old wind slabs on a range of aspects at high elevations. The mid-January crust is now buried beneath 80-150 cm of settled snow and may remain sensitive to large triggers - especially in thinner snowpack areas in the north part of the region. Large, looming cornices exist, they are fragile, and they demand respect. Cornice falls are very effective triggers for avalanches on the slopes below them.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.