Wind slabs may remain reactive to rider triggers on a variety of aspects due to recently shifting wind direction. The air is cold but the March sun can be strong so avoid exposure to cornices and watch for signs of warming on steep south aspects. Thin rocky areas will remain a concern for triggering deeply buried weak layers in this complex snowpack.
Strong winds have formed firm wind slabs that may be found unusually low on slopes. Recent wind has varied in direction meaning wind slabs can be found on all aspects.
Cornices have seen significant growth recently. They can become weak in the strong sun. Give them a wide berth whether travelling on or below ridgelines. Cornices can be dangerous on their own and they can also act as large triggers to deep slab avalanches on slopes below.
Weak, sugary crystals at the bottom of the snowpack produced large avalanches just over a week ago. These avalanches are most likely to be triggered by large loads such as cornice falls. However, in shallow snowpack areas they can also be triggered by the weight of a person and could propagate out to deeper snow resulting in large, destructive avalanches.
Prior to the weekend there were numerous reports of natural wind slab and cornice-triggered avalanches up to size 2.
Over a week ago, several large deep persistent slab avalanches were reported in the alpine, including a natural size 3 near Kispiox, a cornice-triggered size 2.5 at Hudson Bay and several explosive controlled size 2-3 near Ningunsaw.
A dusting of new snow may sit over extensively wind affected surfaces at upper elevations. Cornices are large and can be found on a number of aspects. A thin sun crust may be found on steep solar aspects.
In sheltered areas, 40-50 cm of settling snow may be sitting over a layer of small facets and low density snow that feels upside down.
Several other crusts, layers of facets, or surface hoar can be found in the top 150 cm of the snowpack, but have not shown any significant avalanche activity or snowpack test results recently.
The lower snowpack consists of weak, basal facets which may become active with any rapid change or shock to the snowpack, such as heavy loading or dramatic warming. Snowpack depths range from 60 to 280 cm at treeline.
Sunday night
Scattered cloud. Moderate southeasterly wind. Alpine low -20 ºC.
Monday
Mix of sun and cloud. Moderate southeasterly wind easing to light. Alpine high -17 ºC.
Tuesday
Mix of sun and cloud. Moderate southeasterly wind. Alpine high -16 ºC.
Wednesday
5-10 cm of new snow. Strong southeast wind. Alpine high -12 ºC.
More details can be found in the Mountain Weather Forecast.
