Recent shifting winds have been driving a wind slab problem at higher elevations. Slabs have proven especially touchy where they overlie a recent rain crust.
Summary
Confidence
High -
Weather Forecast
Monday: A mix of sun and cloud. Light to moderate southeast winds. Freezing level to 900 metres with alpine temperatures of -7. Tuesday: Cloudy with sunny periods and flurries beginning in the afternoon. Light southeast winds. Freezing level to 1000 metres with alpine temperatures of -3. Wednesday: Mainly cloudy with scattered flurries bringing a trace to 5 cm of new snow. Moderate to strong southeast winds. Freezing level to 1100 metres with alpine temperatures of -2.
Avalanche Summary
Reports from Saturday include observations of a natural avalanche cycle in the Howson Range, where several Size 2.5-3.5 storm slabs released naturally from north to east aspects between 1200-1700 metres. A MIN report from the Telkwa area also details a snowmobile triggered Size 2.5 wind slab. The March 14 crust mentioned in our snowpack discussion was identified as the failure plane in this occurrence as well as in a skier triggered Size 2 wind slab north of Kispiox. These close calls should draw attention to the extent of recent wind transport as well as the March 14 crust's excellent performance as a sliding layer.
Snowpack Summary
At treeline and above, ongoing winds have been redistributing recent storm snow and light new snow amounts into wind slabs in lee terrain. New snow amounts taper with elevation and lie over a supportive crust (March 14) at about 1300 metres and below. This crust has been observed at higher elevations in the Telkwa area, and wind slabs have proven especially reactive where they sit above it. At higher elevations, wind redistribution is incrementally loading a weak interface that was buried in late February. The interface is composed of facets, crusts, and surface hoar and may be 40-60 cm deep. There's still some uncertainty around the distribution and reactivity of this interface, but it has proven reactive under skier traffic in the north of the region. The mid-pack is well consolidated, but sits above weak, sugary snow near the ground. This deep basal weakness remains an ongoing concern in thin rocky start zones and in shallow snowpack locations.
cgarritty,
Avalanche Canada
