Regions
Northwest Inland.
Strong winds have been redistributing loose snow into new wind slabs. This is likely to be limited to alpine terrain, but a buried weak layer could make any new slabs at treeline elevations particularly reactive.
Weather Forecast
Saturday night: Becoming clear. Strong northwest winds easing slightly. Freezing level returning to valley bottom.Sunday: A mix of sun and lower level cloud. Light variable winds. Alpine high temperatures around -6.Monday: Mainly cloudy. Light variable winds. Alpine high temperatures around -2, a bit cooler at lower elevations under a mild temperature inversion.Tuesday: Increasingly cloudy with possible isolated flurries and trace of new snow. Light to moderate southwest winds increasing over the day. Alpine high temperatures around -3 with a continuing mild temperature inversion and possible above freezing layer at around 1500 metres.
Avalanche Summary
No new avalanches have been reported in the region.A large (size 2.5) storm slab avalanche was triggered remotely (from 20 metres away) by a skier in the Howson Range on Tuesday. This occurred on a southwest aspect at 1700 metres and the slab had a depth of about 30 cm. It is likely that the failure plane in this slide was some variation on the surface hoar and crust combination described in our snowpack summary. This weak layer is one of our primary concerns in the region and can be expected to produce human-triggered avalanches in areas where the overlying new snow has settled into a slab.
Snowpack Summary
Light snowfall and strong winds have been creating a new surface of wind-affected snow. Beneath the evolving surface, we have around 30 cm of newly wind-affected snow from snowfall earlier in the week. A thin crust may be found within this layer.At alpine and high treeline elevations, this recent snow sits on old wind-affected and faceted snow, and possibly over a weak layer of surface hoar in more protected areas. The recent snow sits on a rain crust/surface hoar combination below about 1600 m. This weak interface has been one of our primary avalanche problems, particularly as wind and warming worked to transform the overlying snow into a more cohesive slab.Under the interface described above, the mid snowpack is generally strong. Faceted (sugary) snow is present in this part of the snowpack, but the overall dense structure here helps to overcome the weakness of these grains.The bottom 30 to 50 cm of the snowpack consists of a weak layering of facets and crusts, particularly in areas where the snowpack is thin. It may be possible for large slab avalanches to step down down to ground in these thin snowpack areas, resulting in even larger avalanches.
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.