Sheltered, shady terrain may still hold soft snow that doesn't sit on top of a crust. Watch for signs of reactive windslabs like shooting cracks and hollow, drum-like sounds. Avoid shallow rocky start zones where you could trigger a deep persistent slab.
Last week's storm snow has been redistributed by moderate to strong winds from the northwest through southeast.
Expect these windslabs to be more reactive where they are sitting on top of a crust.
Be cautious at ridge crests, on convex rolls, and in cross-loaded features.
The early December crust can be found 80-150 cm deep.
This deep persistent slab problem has been less active over the weekend, but we have been reminded multiple times in the last month that this layer could remain a concern all winter.
Thin rocky start zones are the most likely place to trigger this layer. Also, daytime warming, solar radiation, cornice fall, and step-downs from smaller avalanches could increase the chance of an avalanche on this layer.
Monday Night: Mostly cloudy, clearing by the morning. 0-2 cm of snow expected. Light west wind with periods of moderate northeast at higher elevations. Freezing levels drop to near valley bottom. Alpine low around -7 C.
Tuesday: Partly cloudy. Possible trace of snow expected. Light winds in the morning trending to moderate from the west in the afternoon, and strong northwest at higher elevations. Freezing levels rise to 1000 m by the afternoon. Alpine high around -5 C.
Wednesday: Scattered clouds. Possible trace of snow expected. Light west wind trending to extreme northwest at higher elevations. Freezing levels near valley bottom overnight, rising to 750 m by the afternoon.
Thursday: Mostly sunny. No new snow expected. Light southwest winds trending to strong northwest at higher elevations. Freezing levels at valley bottom overnight, rising to 750 m by the afternoon.
No new avalanches were reported on Sunday or Monday before 4pm.
On Saturday, neighbouring Waterton National Park reported a few natural windslab avalanches to size 2 on solar aspects in the alpine.
A Mountain Information Network (MIN) post from west of Elkford reported a large avalanche that looks to be a couple of days old due to snow on top of the debris. It failed below some cliffs in the alpine and ran into flatter terrain below. See here for more details.
On Friday morning the field team reported four new wind slabs size 2.5 to size 3 that looked to fail on the (re-loaded) early December interface in the Crowsnest North. One of these appeared to be triggered by a cornice fall.
A possible dusting of new snow will not cause significant change to the snowpack. Moderate winds continue to affect the surface snow, building fresh, thin windslab. Expect to find a thin suncrust on solar aspects, especially in the high alpine, where temperatures may have gotten above zero over the weekend.
The upper snowpack is variable throughout the region with a melt-freeze crust found 10-20 cm down (aspect and elevation dependant, maybe even on the surface in windward terrain). This crust is less likely to exist above 2000 m.
One common theme throughout the region is that the mid-pack is well settled above the deeper December crust/facet interface which is currently the primary concern in the snowpack.
The early December crust is now generally down 80-150 cm. This layer is found widespread through the region but with varying test results. Recent snowpack tests have shown more reactivity in shallower snowpack areas as well as the potential for step down avalanches. This indicates that there is potential to trigger this weak layer from a thin spot which may propagate to a thicker slab within the snowpack, creating a very large avalanche.
Daytime warming, solar radiation, and cornice fall could all play a role in triggering deep persistent slabs.
