Avalanche Forecast

Tuesday night: Cloudy, 15-25 cm of snow, moderate southwest wind, alpine temperature -2 C, freezing level rising to 1000 m.

Wednesday: Cloudy, 5-15 cm of snow tapering by midday, moderate west wind, alpine temperature -7 C, freezing level dropping to valley bottom.

Thursday: Partly cloudy, light northwest wind, alpine high temperature -9 C.

Friday: Cloudy, 5-15 cm of snow, moderate southwest wind, alpine high temperature -9 C.

Reports of a widespread natural avalanche cycle in the afternoon Tuesday revealed touchy storm slabs breaking 15-25 cm deep. Expect storm slabs to become larger and more reactive as more snow accumulates by Wednesday morning. Storm slab avalanches have the potential to step down to multiple buried weak layers producing large and destructive avalanches. 

There have been many recent reports of large (size 2-3) avalanches from both natural and human triggers on a variety of aspects and elevations. These avalanches have been breaking 50-100 cm deep on surface hoar layers from mid to late December. Several of them have been remote-triggered. The most recent example, reported yesterday, released naturally with loading from new snow and wind. These avalanches give clear evidence that the continual loading on this fundamentally weak snowpack structure remains a serious concern.

Within the past week, three notable deep persistent slab avalanches released naturally on east and northeast facing slopes above 2200 m in the southern part of the region on a crust/facet layer from late November buried 150 cm deep. 

Up to 60 cm of new snow is forecast to accumulate by Wednesday afternoon with moderate to strong southwest wind. This will form a storm slab problem that will need to be managed conservatively. Expect areas where the snow is being drifted by wind to be more reactive. 

Two layers of surface hoar from mid and late December are now buried 60-120 cm deep. These layers continue to produce large avalanches across aspects and elevations. Small avalanches in the new snow have the potential to step-down to these persistent weak layers.

A facet/crust layer from late November lingers near the bottom of the snowpack. This layer has shown reactivity in isolated areas in the southern part of the region.

• Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
• Be careful to keep storm day fever from luring you out into bigger terrain features.
• If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.