Avalanche Forecast

A fast-moving storm plows through overnight and hammers the region with snow and wind.

Friday night: Cloudy, 20-40 cm of snow above 1000 m, strong southwest wind, alpine temperatures rising to -5 C, freezing level reaching 1000 m and dropping to 700 m by morning.

Saturday: Cloudy, 5-15 cm of snow, strong southwest wind, alpine temperatures cooling from -6 C to -11 C, freezing level dropping from 1000 m to 500 m.

Sunday: Cloudy, 5-15 cm of snow above 500 m, light southwest wind, alpine temperatures near -12 C. 

Monday: Cloudy with sunny breaks, 5-15 cm of snow, light winds becoming east, alpine temperatures near -9 C, freezing level near 600 m.

We expect that natural and human triggered avalanches will release large and run far on Saturday. Cornices could reach their breaking point and trigger large avalanches on slopes below.

A powerful storm with strong wind is forecast to bring 30-60 cm of new snow to the mountains by the end of Saturday. This will create a widespread, reactive storm slab problem that will be particularly pronounced where the snow is drifted by southwest winds. The snowpack will need time to adjust to this rapid, hefty load. Closely monitor how the new snow is bonding, as the cold snow is not expected to bond well to previous snow surfaces. Cornices are large and looming and could reach their breaking point.

The snowpack around treeline is complex and warrants conservative route selection. Weak faceted snow can be found near two possible crust layers that formed in early December. This crust-facet combination may become reactive with rapid loading. Our models suggest that this persistent slab problem may be most pronounced at elevations between 1400-1800. Any steep opening in the trees should be treated as suspect right now.

Average snow depths vary drastically with elevation, with 320-400+ cm in the alpine, 120-200 cm at treeline, and a drastic drop to below the threshold for avalanches below treeline. With this storm event, a greater number of areas at or below treeline elevations may meet the threshold for avalanches. 

• Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
• Expect slab conditions to change drastically as you move into wind exposed terrain.
• Stick to simple terrain features and be certain your location isn't threatened by overhead hazard.
• Cornice failures could trigger very large and destructive avalanches.
• The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.