It's all about the new snow, but accumulations and slab properties vary across the region. Treat the depth of new snow as one component of destructive potential, and slab properties as the multiplier of this potential. Avalanche danger will be greatest where deep new snow and signs of slab formation (like wind loading or shooting cracks) come together.
Newly formed, reactive slabs on north through east aspects are now scattered around the region as a result of the weekend storm. Larger, more reactive, and more widespread slabs should be expected in the Pine Pass area and the MacGregors, snowfall hotspots during the storm.
In higher snowfall parts of the region, deep accumulations of new snow that haven't formed into a slab are likely to create large sluffs with rider traffic in steep areas.
Limited observations from the weekend storm showed small dry loose avalanches releasing with skier traffic below treeline. We also expect some degree of a natural avalanche cycle took place at higher, wind affected elevations, and in areas like Pine Pass and the MacGregors, where up to about 40 cm of new snow accumulated.
Earlier in the week there was evidence of deep persistent slab activity that likely occurred during last weekend's storm with avalanches up to size 3.5. While we currently expect the deep weak layer to be dormant, riders should continue to avoid steep, thin, rocky slopes where triggering a deep persistent avalanche would be most likely, particularly near alpine ridgelines.
Looking forward, we expect new wind slabs from Saturday's storm will remain sensitive to human triggering for a bit longer than usual, owing to the weak faceted snow they overlie.
From 20 up to about 40 cm of new snow fell in higher snowfall areas of the region like Pine Pass and the MacGregors over the weekend, with one operator in the MacGregors reporting up to 80 cm! Closer to 5-15 cm fell in eastern locations like Tumbler and Kakwa.
The new snow overlies faceted (sugary), heavily wind affected snow from recent cold temperatures and north winds. This means a mix of stubborn, old, faceted winds slabs may still be found on south-facing aspects while newer, more reactive wind slabs exist on more north-facing aspects.
The middle of the snowpack is generally strong.
A weak layer of large and weak facets is found near the base of the snowpack. The layer is currently considered dormant, except perhaps in very steep alpine terrain that is inherently shallow. Riders should continue to avoid thin, rocky terrain where the likelihood of triggering this layer is higher.
Monday night
Mainly cloudy with scattered flurries and up to 5 cm of new snow. Light southeast winds.
Tuesday
Mainly cloudy. Light east winds. Treeline high temperatures around -14 °C.
Wednesday
Increasing cloud and flurries with a trace of new snow by end of day, increasing overnight. Winds becoming strong southwest. Treeline high temperatures around -10.
Thursday
Cloudy with continuing snowfall bringing 10-20 cm of new snow, including overnight amounts. Strong southwest winds easing a bit over the day. Treeline high temperatures around -9.
More details can be found in the Mountain Weather Forecast.
