Step back to conservative terrain as the storm slab problem gets trickier. Strong winds and snow are expected Saturday afternoon.
A buried surface hoar layer may increase reactivity, and small avalanches may step down to deeper weak layers.
Two concerning persistent weak layers can be found in the top meter of the snowpack. The first is a surface hoar/crust layer from early December and the second is a surface hoar, facet or crust layer from mid November. These layers are most concerning on sheltered treeline features where surface hoar is most likely to be preserved.
Fresh snow and strong winds will develop new and reactive slabs. Expect winds to redistribute snow at treeline and alpine elevations into deeper and more reactive slabs in wind loaded features. Where strong winds are observed slabs could be found further down slope than expected.
Expect slabs to be reactive as they sit over a variety of weak surfaces - facets, a crust and/or surface hoar.
On Thursday loose dry avalanches to size 2 were reported in steep terrain features.
On Tuesday explosive control produced a few small avalanches, up to size one.
A natural size 2.5 persistent slab avalanche was reported, thought to have occurred on Tuesday. This avalanche occurred on a northeast aspect, 2000 m on a reloaded bed surface.
New snow accumulates over the day, redistributed into larger deposits in east and north facing terrain. Slabs form over facets, surface hoar or a crust and may not bond well.
Around 50cm deep a layer of surface hoar at treeline and a thin crust on steep south facing slopes exists. This layer was formed in early December and is less widespread than the other layers of concern in the snowpack.
The mid-November layer consisting of facets and surface hoar is now buried around 80 cm deep.
The snowpack in the forecast region is quite variable and increasingly complex with snowpack depths at treeline varying from 100cm to 200cm.
Friday Night
Cloudy with 5 cm of snow expected. Moderate westerly winds. Freezing levels below valley bottom.
Saturday
Mostly cloudy with around up to 15cm of new snow expected late afternoon. Strong to extreme southwest winds and a high of -16°C
Sunday
5-10 cm possible overnight. Mostly cloudy with light flurries bringing trace amounts of new snow. Moderate westerly winds. Freezing levels around 500 m, high temperatures of -10°C.
Monday
Cloudy with 5 cm of snow expected. Strong southwest winds return. Freezing levels rise, to around 1000 m with an above freezing layer possible at 2000 m. High temperatures of 0°C.
More details can be found in the Mountain Weather Forecast.
