Lizard-Flathead

Warmth will be transforming our previously low density storm snow into more cohesive slabs over the coming days. The concern is greatest at mid elevations where wind loading and buried surface hoar are most likely to coexist.

High -

Thursday night: Cloudy with clear periods and isolated flurries with a trace of new snow. Light southwest winds increasing to strong northwest in the alpine.Friday: A mix of sun and cloud. Moderate northwest winds increasing to strong in the alpine. Winds increasing overnight. Alpine high temperatures around -5.Saturday: Mainly sunny. Strong west winds reaching extreme in the alpine and increasing overnight. Alpine high temperatures around 0 to +1 as freezing levels jump to a possible 2500 metres.Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Extreme northwest winds decreasing to moderate over the day. Alpine temperatures dropping from around 0 to -4 over the day as freezing levels decline from 2000 to 1000 metres.

Avalanche observations from Wednesday were limited to smaller (size 1-1.5) loose dry sluffs and small slabs releasing naturally from steep alpine features.On Monday, explosives triggered size 2 storm slab avalanches and cornices. Our 10-30 cm-deep weak layer of surface hoar was the failure plane.Skier-triggered, cornice-triggered, and natural storm slab avalanches were reported mainly on north-northeast aspects from 1700-2000 m over the weekend, including a snowboarder triggered a size 2 avalanche on a south aspect in open trees outside the Fernie boundary, fortunately with no injury. Two large snowmobile triggered avalanches were reported over a week ago. One was triggered on a thin, rocky, southwest facing feature near ridge crest north of Fernie (report here). The other was triggered on a wind affected south facing slope at treeline in the Corbin area (report here). Deep persistent slab activity has been most common in parts of the region with shallow snowpacks (such as near the continental divide) and alpine features with thin variable snowpack depths.

10-30 cm of new snow forms the snow surface, the product of snowfall this past weekend. In alpine and treeline areas, winds have been redistributing this storm snow, loading lee terrain features, and building cornices. Lower down, the recent snow is sitting over a weak layer of surface hoar and sun crusts. The surface hoar is most prominent around treeline elevations (1500-1900 m). On solar aspects and below treeline, the surface hoar and new snow overlie sun and temperature crusts.In shallow snowpack areas, the base of the snowpack may still be composed of weak faceted grains. In deeper snowpack areas, the middle and lower portions of the snowpack are generally considered to be well-settled and strong.