Stick to conservative terrain during the storm and make observations of slab formation and reactivity as new snow piles up. Buried crust and surface hoar may create quite touchy conditions.
Persistent weak layers of crust/facets or surface hoar are buried in the upper 250 cm of the snowpack. Distribution seems spotty and signs of instability may not be evident. The best defence is choosing smaller, low-consequence terrain.
Around 30 cm of new and recent snow will have accumulated on a variety of surfaces by end-of-day Saturday, the most concerning being surface hoar and sun crust, providing either a firm bed surface or a delicate weak layer for new storm slabs.
In the past few days, a couple of natural wind slabs, size 2-2.5 were observed on north and east aspects in the alpine.
Several recent natural cornice falls have been large enough that, even without triggering a slab, were size 2.5 or greater.
A few very large persistent slab avalanches have been reported throughout the region in recent days. Some are suspected to have run on the mid-March layer, and others even deeper. Most of these avalanches were triggered by cornices.
10 to 20 cm of new snow should accumulate by end-of-day Saturday, burying wind slabs and wind-affected surfaces in exposed areas and adding to about 15 cm of new snow in more sheltered areas.
Collectively, the new snow overlies a sun crust on steep solar aspects and up to 40 cm of faceted snow in sheltered areas. At least one operator, in the Terrace area, has observed 6 mm surface hoar at the new snow interface, buried on March 2.
A layer of facets and/or surface hoar from earlier in March can be found 50 to 100 cm deep.
Several older persistent weak layers are buried up to 250 cm deep. While triggering these layers is trending toward unlikely, they present a low-probability, high-consequence problem.
Friday Night
Cloudy with continuing flurries bringing 5 to 10 cm of new snow. 30 km/h southwest ridgetop wind. Treeline temperature around -3 °C.
Saturday
Cloudy with easing flurries bringing 5 to 10 cm of new snow. 20 to 30 km/h southwest ridgetop wind, easing. Treeline temperature -3 °C.
Sunday
Mostly cloudy with scattered flurries bringing up to 5 cm of new snow, including overnight. 15 to 30 km/h southeast ridgetop wind, increasing. Treeline temperature approaching 0 °C as freezing level climbs to 1300 m.
Monday
Mostly cloudy with flurries continuing from overnight bringing 15 to 30 total cm of new snow to the alpine, diminishing with elevation to mostly rain below 900 to 1100 m. 20 to 50 km/h southwest ridgetop wind, easing. Treeline temperature -1 °C. Freezing level falling from 1300 m to 900 m during the storm.
More details can be found in the Mountain Weather Forecast.
