Avalanche Forecast

Saturday night: Cloudy, 5-15 cm of snow, southwest wind decreasing to light, alpine temperatures dropping -12 C, freezing level near valley bottom.

Sunday: Cloudy, 5-15 cm of snow, moderate southwest wind, alpine temperatures near -11 C, freezing level around 500 m. 

Monday: Cloudy, 5-10 cm of snow, moderate winds shifting east, alpine temperatures near -9 C, freezing level around 500 m.

Tuesday: Mostly clear, light variable winds, alpine temperatures near -11 C, freezing level near valley bottom.

We expect natural and human triggered avalanche activity to continue on Sunday. Cornices could reach their breaking point and trigger large avalanches on slopes below. 

A natural avalanche cycle occurred early Saturday morning that produced several large (up to size 2.5) avalanches releasing in the storm snow. Operators just east of the region reported one very large (size 3-3.5) avalanche. Below treeline, operators reported several natural small (size 1) avalanches out of steep rocky terrain. Riders near Brohm Ridge shared photos in this MIN report of touchy conditions below treeline on Saturday morning.

Intense bands of precipitation are forecast to bring another 10-30 cm of snow to the mountains in a highly localized pattern. Sustained southwest winds will have an ongoing supply of snow to drift into reactive wind slabs at upper elevations. Avoid freshly wind-loaded terrain features on Sunday (for example, down-wind of ridges and roll-overs).

A powerful storm on Friday night brought 25-40 cm of new snow to the mountains with strong southwest winds. A gradual temperature rise during the storm created warmer denser snow over colder lighter snow. In many locations, storm accumulations sit on crust layers that formed in early December. This tricky combination of slab and sliding surface may require more time to recover and gain strength, and it warrants careful evaluation and cautious routing-finding. 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 near and below treeline elevations are meeting the threshold for avalanches. 

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• 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.
• Choose low-angled, sheltered terrain where new snow hasn't been wind-affected.