Plan for stability to worsen over the day as new snow adds up and wind loads it into deeper deposits. Watch for signs of slab formation like shooting cracks letting you know it's time to back off into mellow terrain.
Another round of new snow and wind will be forming reactive new wind slabs on Sunday. The freshest, touchiest slabs are expected to form in the lee of forecast south winds (think north slopes), but recent, potentially still reactive slabs may already be found on a wide range of aspects.
Saturday night: Cloudy with continuing isolated flurries. Light east or northeast winds.
Sunday: Cloudy with flurries bringing about 10 cm of new snow, continuing overnight. Light south winds, increasing over the day and overnight. Alpine high temperatures around -6.
Monday: Cloudy with continuing flurries and up to 10 cm of new snow, including the overnight period, easing over the day. Light variable winds becoming westerly. Alpine high temperatures around -4.
Tuesday: Cloudy with continuing isolated flurries and a trace of new snow. Strong northwest winds. Alpine high temperatures around -4.
Reports from the first hours of Saturday's storm describe small (up to size 1) loose snow releases triggerable on south to west aspects at treeline on the North Shore. Formation of new wind slabs was observed on northwest aspects. Expect these hazards to be a couple of notches more dangerous on Sunday as snow accumulates and elevated winds continue to shift around.
Including Saturday's 5 cm of new snow, roughly 15 cm should accumulate in the region by the end of the day on Sunday. Winds in advance of and during this snowfall have been at times strong at higher elevations and expected to undergo a shift from northeast to south, meaning reactive new wind slabs should be expected on a wide range of aspects.
The surface beneath our accumulating snow consists of a thin cover of lower density (likely faceted) snow (where not already windblown) over a mix of thin breakable crust and yet more old wind-affected snow. 30-40 cm of gradually faceting storm snow below this mix, a more supportive crust solidly caps the snowpack below about 1400 metres. This crust may be absent at higher elevations.
100-150 cm of snow sits over a widespread persistent weak layer. This weak layer consists of a thick crust with weak facets on top of it in many areas. In most areas where it remains preserved, this layer is likely not triggerable due to bridging by overlying dense snow and crusts (this applies to the North Shore). There is some uncertainty about the possibility for continued reactivity at this interface in steep terrain at higher elevations in the interior and north of the region, but only where it has not previously avalanched and where the overlying snowpack may have failed to form an effective bridge over it.
Click here to check out North Shore Rescue's snowpack update from February 12. It's an excellent snapshot of conditions on the North Shore in advance of the current storm pattern.
