Heavy snow and warm temperatures are expected on Saturday which will result in dangerous avalanche conditions. Travel in avalanche terrain is not recommended.
An increasingly reactive storm slab will develop as snowfall accumulates and is impacted by wind. Rain and rising freezing levels will encourage loose-wet avalanches at lower elevations.
Facetted, weak snow at the base of the snowpack is a cause for concern with forecasted weather. Rapid loading from new snow and wind or rapid warming from rising freezing levels or rain can stress previously inactive weak layers in the snowpack. If this layer "wakes up" with increasing load and temperatures, it will produce large and destructive avalanches.
Friday night: around 10 cm new snow at high elevations, rain lower down. Strong southwest winds. Freezing level around 2000 m.
Saturday: around 20 cm snow expected with the potential for 30-40 cm in isolated areas in eastern areas. Expect rain at lower elevations. Strong to extreme southwest winds shifting to northeast in the afternoon. Freezing level around 1700 m.
Sunday: Dry and sunny. Light northwesterly winds. Freezing level around 500 m.
Monday: Dry with sunny breaks. Light notheasterly winds. Freezing level at surface with alpine temperatures around -10C.
On Thursday a cornice fall released a size 2 slab avalanche on the slope below on an east aspect at 2150 m.
On January 16th, a natural, size 2 wind slab stepped down to the deep persistent basal facets below a rock band, details here.
Expect an increase in avalanche activity with the passage of the storm on Saturday, particularly in areas that see substantial amounts of new snow.
New snow combined with strong southwesterly winds will continue to build slabs in exposed areas. Cornices have been noted in many areas. A crust can be found up to around 1700 m due to previous warming and sun exposure.
A well consolidated mid-pack overlies a generally weak basal snowpack. The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. While there has been little in the way of avalanche activity on this layer recently, the warm wet storm impacting this region has the potential to wake this layer up again. Areas that are most likely to harbor this problem are shallow, rocky start zones.
