A skier-triggered deep persistent slab in the Birkenhead area on Friday suggests that a deeply buried weak layer is still in play. Avoid large steep slopes, especially where the snowpack depth is variable. Also watch for pockets of wind slabs in atypical areas.
Northerly outflow winds have left stiff wind slabs at upper elevations. Watch for wind-loaded pockets, especially just below ridgetops and in extreme and very steep terrain. Wind slabs may be particularly reactive to where they overlie a hard crust.
A layer of large and weak facets sits near the base of the snowpack. This layer is most likely to be problematic in steep, unsupported, wind-loaded terrain or by first triggering a layer in the upper snowpack. Evidence suggests this layer may be more problematic in the Hurley and Birkenhead areas.
Reports from the past few days are limited to one small wind slab avalanche (size 1.5) from Sunday. It occurred naturally on a reverse-loaded feature in the Hurley area. On Friday, a size 2.5 skier-triggered deep persistent slab occurred in the Birkenhead area. This avalanche was remotely triggered, meaning the skier was a distance away from the slab when it occurred (100 m above). It occurred on a wind-loaded slope in the alpine during a period of strong solar radiation. The crown was 150 cm deep.
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Northerly winds have affected open areas in the alpine and treeline, scouring windward slopes and creating pockets of wind slabs in lee areas. In sheltered areas, 10 to 20 cm of recent storm snow is faceting with cold temperatures. A surface crust can be found below 1800 m and all elevations steep solar aspects.
In the midpack, a weak layer can be found 50 to 100 cm deep, as a decomposing crust, or in many places, it's more of a soft and weak section of the snowpack. There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack.
Generally, the snowpack in this region is weak and shallow. Snowpack depths around treeline are highly variable and range between 150 to 250 cm.
Tuesday night
Cloudy with light flurries bringing trace amounts of snow, 30 to 40 km/h southwest wind, treeline temperatures around -10 ˚C.
Wednesday
Mostly cloudy, isolated flurries with trace amounts of snow, 30 to 40 km/h southwest wind, treeline temperatures warm to -7 ˚C.
ThursdayMix of sun and cloud, no precipitation, 30 to 50 km/h south wind, treeline temperatures warm to -5 ˚C.
FridayCloudy with scattered flurries bringing 1 to 5 cm of new snow, 40 to 60 km/h south wind, treeline temperatures warm to -3 ˚C.
More details can be found in the Mountain Weather Forecast.
