Heavy snow and warm temperatures are expected on Saturday which will result in dangerous avalanche conditions. Travel in avalanche terrain is not recommended.
Snow falling with strong winds and rising temperatures will develop increasingly reactive storm slabs. Expect to find the most reactive deposits in open areas, around ridge features, and lee terrain - places where wind has redistributed loose snow. Rain and rising freezing levels will encourage loose-wet avalanches at lower elevations as freezing levels rise and the snowpack warms.
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 1900 m.
Saturday: 15-25 cm new snow, rain at lower elevations. Strong to extreme southwest winds. 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 number of natural wind slab avalanches were observed up to size 2.
With anticipated new snow and rising temperatures, avalanches will become much more likely on Saturday.
Recent storm snow combined with southwest winds have producing slabs in the alpine and exposed tree line areas. Cornices have been noted along ridgelines. The recent snow covers a temperature crust which formed up to around 1600 m.
The upper snowpack continues to settle in mild temperatures. Several crust layers exist in the mid-pack as a result of previous warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity. The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although this basal layer has not been an active avalanche problem in the region since December, if there's anything that will wake it up again, it's a warm, moist storm, such as the one forecast for Saturday.
