Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. We are confident about the likelihood of avalanche activity, what is less certain are their possible size.

Another powerful storm is expected to move in Friday night

Thursday night: Clearing overnight, no new snow expected, light west winds, low treeline temperatures near -6 C, freezing level dropping to 300 m.

Friday: Increasing cloudiness, no new snow expected, light winds becoming southwest, high treeline temperatures near -4 C, freezing level around 500 m.

Saturday: Overcast, 20-35, 25-50 mm of precipitation is expected by the end of the day, strong southwest winds with extreme gusts, treeline temperatures rising to near +1 C, freezing level rising to around 1200 m.

Sunday: Cloudy, 10-20 cm of snow, mm of precipitation, southwest winds decreasing from moderate to light, high treeline temperatures dropping from 0 C to -3 C, freezing level around 700 m.

The likelihood of human-triggering large, destructive avalanches is increasing. On Thursday, we received reports of two large (size 2-3) avalanches that released on a persistent weak layer on northwest and southwest aspects between 1700-1900 m. Notably, skiers remote-triggered these avalanches while traveling uphill. Several small (size 1-1.5) sympathetic avalanches also released on nearby terrain features during these close calls. Operators also reported a small (size 1.5) explosive-triggered persistent slab on a steep north aspect at 1900 m. 

Additionally, operators on Thursday reported small (size 1) very soft slabs triggered by both skiers, explosives, and loose snow falling off of rocks. Smaller avalanches in recent snow have the potential to step-down to deeper layers and produce large avalanches.

Winds shifted to the north on Thursday and may have created a tricky reverse-loading pattern. Avoid slopes where the snow feels stiff or slabby, and seek out softer conditions in wind-sheltered terrain.

The primary layer of concern is a weak layer of facets (sugary snow) above a widespread crust down 100-180 cm that formed in early December. On Thursday, this persistent slab problem surprised several recreationists with large, remotely-triggered avalanches. This problem is particularly hard to predict, tricky to manage, and will likely continue to surprise complacent backcountry travelers. Given recent remote-triggered and sympathetic avalanche activity, these conditions require wide, conservative terrain margins and disciplined backcountry travel techniques.

• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Remote triggering is a concern, avoid terrain where triggering slopes from below is possible
• Uncertainty is best managed through conservative terrain choices at this time.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Cornice failures could trigger very large and destructive avalanches.