Wind slabs and cornices continue to be the main concern with ongoing strong southerly winds and new snowfall. Extra caution is required around Stewart and north where a deeply buried layer of surface hoar has recently become reactive.
Summary
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
5-10cm of new snowfall is expected on Saturday with freezing levels around 1000m and strong alpine winds from the southeast. Light snowfall (3-6cm) and sunny breaks are expected on Sunday with freezing levels around 1000m and strong alpine winds from the southeast easing in the afternoon. Light scattered flurries are forecast for Monday with freezing levels around 1000m and light alpine winds.
Avalanche Summary
On Thursday, a natural size 3.5 persistent slab avalanche was reported in Bear Pass. The occurred on a northwest aspect at 1350m elevation and released on the late-February surface hoar layer. A natural size 2.5 storm slab was reported from the same area and appears to be on a northern aspect. A skier triggered a size 2 cornice in the same area which did not trigger a slab on the slope below. Loose wet sluffing and a couple natural glide avalanches were reported from below treeline. Sunny breaks in the northern part of the region on Wednesday led to a few natural cornice falls and slab avalanches up to size 3 on steep solar aspects. There were also reports of a few natural wind slabs up to size 2.5 from wind-loaded alpine slopes. Skier testing produced a few size 1 wind slabs in steep lee terrain. Wind slabs are expected to be touchy on Saturday with ongoing wind loading. There is extra concern for the deep surface hoar layer that seems to be reactive north of Stewart. This likely would require a heavy trigger like a cornice or smaller avalanche stepping down.
Snowpack Summary
Ongoing light snowfall and strong winds have shifted the new snow into hard or soft wind slabs at treeline and in the alpine, maintaining a wind slab problem on northerly aspects and scouring leeward slopes. Areas north of Stewart are reporting a weak surface hoar layer down 70-100cm which sits below the last week of accumulated storm snow. In the south of the region, an old crust buried in early February can now be found around 80-120 cm below the surface. This crust, which may coexist with small facets or decomposing surface hoar, recently produced sudden planar ("pops") results in snowpack tests. Although no recent avalanches were reported to have failed at this interface, I'd remain suspicious of this layer in steep, unsupported terrain at treeline and in the alpine.
rbuhler,
Avalanche Canada
