Flurries and gusty winds continue to build storm slabs and add load to weak layers at the bottom of the snowpack.
Continued flurries and gusty winds will contribute to an ongoing storm slab problem. Expect to find the most reactive deposits in open areas and around ridge features at treeline and above.
Between Thursday and Saturday, in the northern part of the forecast region, weak layers at the bottom of the snowpack were stressed by the recent storm snow, and resulted in very large deep persistent slab avalanches failing naturally and from skier traffic. Two layers have been a concern in the north including a 100 cm deep surface hoar layer in sheltered areas around treeline and weak, facetted snow near the bottom of the snowpack in shallow rocky start zones at higher elevations. Ongoing loading from snow and wind will continue to stress weaknesses at the bottom of the snowpack.
SUNDAY NIGHT: Scattered flurries, 5-10 cm. Alpine low temperature -7 C. South wind 20 gusting to 50 km/hr. Freezing level 900 m.
MONDAY: Scattered flurries, 5-15 cm with higher snowfall amounts favoring the Coquihalla. Alpine high temperature -6 C. Southwest wind 20 gusting to 45 km/hr. Freezing level 1000 m.
TUESDAY: Flurries and snow, 5-20 cm. Alpine high temperature -4 C. Southwest wind 20-40 km/hr. Freezing level 1200 m.
WEDNESDAY: Flurries and snow, 15 cm. Alpine high temperature -3 C. South wind 20 gusting to 50 km/hr. Freezing level 1400 m.
Several very large (size 3) deep persistent avalanches were reported to have failed naturally between late Thursday and Saturday, the reports come from around the Duffey Lake area and further north in the region towards Gold Bridge and Whitecap Mountain. These avalanches occurred on east, north, and west aspects around 2000-2200 m. Additionally, on Friday, skiers remotely triggered a size 3 avalanche on a north aspect at 2100 m in the Duffey area and a size 1 deep persistent avalanche while traveling along a skin track on a west aspect at 2050 m near Whitecap Mountain. On Saturday, a snowmobile remotely triggered a size 3 deep persistent avalanche on a west aspect near Birkenhead Lake Provincial Park. Weak faceted grains and crusts near the base of the snowpack continue to be a concern with additional loading from new snow and wind.
On Thursday, small (size 1) storm slab avalanches failed naturally on northerly aspects. Additionally, a machine triggered a size 2 avalanche on a steep slope below a road at 1800 m. Small (size 1-1.5) wet loose avalanche activity was reported below treeline.
20-40 cm recent storm snow has settled into a slab and been impacted by moderate to strong south-southwesterly winds in the alpine and upper treeline. Colder temperatures have dried out the upper snowpack and wind slabs have developed in open treeline and ridge features and into the alpine. Below 1600 m, the snowpack is well settled and a crust has formed with colder overnight temperatures.
There have been two layers of concern in the northern half of the region (e.g. Duffey, Hurley). One is a weak layer of surface hoar buried about 100 cm deep that professionals are tracking at treeline in sheltered areas. The other is weak faceted grains and crusts near the bottom of the snowpack, this is the failure plan of recent reported deep persistent avalanches and is most likely to be triggered in shallow rocky start zones. There are currently no concerns about deep weak layers in the south of the region (e.g. Coquihalla).
