Flurries and strong wind feed fresh wind slab development at upper elevations, while sustained above-freezing temperatures make for moist snow below treeline on Thursday. Afterwards, easing winds and overnight refreeze will reduce avalanche hazard for the end of the week.
Flurries bringing small amounts of new snow will feed fresh wind slab development. Variable wind direction has resulted in deep pockets of recent storm snow on a variety of aspects. These older wind slabs are likely becoming more stubborn to trigger.
The persistent slab problem is most likely on the eastern slopes of the region (e.g., Kakwa, Tumbler Ridge) and in areas where the snowpack is thin. Steep, rocky slopes with a shallow or thin to thick snowpack in the alpine are the most likely places to trigger buried weak layers. This problem likely won't go away until substantial melt-freeze cycling occurs.
Wednesday night: Partly cloudy. Strong southwest wind. Freezing level 1500 m. Alpine temperature -7.
Thursday: Mostly cloudy with flurries up to 10 cm. Strong southwest wind. Freezing level 1200 m. Alpine temperature -10.
Friday: Mostly cloudy. Light to moderate southwest wind. Freezing level dips to valley bottom overnight, up to 1200 m during the day. Alpine temperature -7.
Saturday: Mostly cloudy. Light to moderate southwest wind. Freezing level dips to valley bottom overnight, up to 1400 m during the day. Alpine temperature -7.
Evidence of large storm slab avalanches (size 3) was observed Monday and Tuesday between Sentinel Pass and Chetwynd, likely having released during the storm on the weekend.
On Sunday we received second-hand information about a size 2-2.5 (estimated) rider-triggered avalanche in the Hasler area.
This great MIN report from Saturday describes natural avalanche activity in Evanoff Provincial Park.
Last Thursday, there were numerous reports of size 2-2.5 explosive triggered avalanches in the Table River Valley.
10-40 cm of recent snow has been redistributed by strong southwest to northwest wind, likely resulting in variable wind loading patterns, with wind slabs possible on many aspects and large, fragile cornices along ridgetops. This snow sits on melt freeze crusts at lower elevations and on solar aspects. Otherwise it adds to 30 to 50+ cm of settling dry snow from last week.
A weak layer of facets buried in mid-February may now be found around 120 to 150 cm deep, or shallower in the east of the region and in thin snowpack areas. The most likely place to trigger this layer is where the snowpack is shallow in alpine terrain. Large loads, such a cornice falls or multiple sleds on the same slope often trigger slopes that a single rider couldn't trigger on their own.
