Avalanche Forecast

A punch of sunshine before cloud and snow roll back in.

Thursday Night: Scattered cloud. Possible trace of snow. Light northwest wind trending to strong at higher elevations. Alpine low around -18 °C. 

Friday: Scattered clouds. Moderate northwest winds, shifting to southwest at lower elevations in the afternoon. Treeline high around -16 °C. 

Saturday: Mostly cloudy. 5-10 cm of snow expected. Moderate to strong south winds, trending to extreme southwest at higher elevations. Treeline high around -15 °C. 

Sunday: Mostly cloudy. 5-10 cm of snow expected overnight, with another 1-3 through the day. Light southwest winds, trending to moderate west at higher elevations. Treeline high around -17 °C.

In the south of the region, the December 1 interface is creating a concerning persistent slab problem near treeline. Until more is known about the nature of this persistent slab problem, conservative terrain selection remains critical and recently wind loaded features around treeline should be avoided. See below.

Wind slabs formed on all aspects in exposed terrain are expected to remain sensitive to human triggers.

On Wednesday a few loose dry avalanches up to size 1.5 were reported out of steep terrain.

On Tuesday, a ski cut triggered a size 2.5 persistent slab near Blue River. This occurred on a treeline feature on a NW aspect at 1800 m and failed on the December 1 crust/facet interface down around 70 cm. This avalanche propagated 150 m wide across multiple sparsely treed features suggesting that the layer has the potential to be highly reactive if triggered. This has been the only recent avalanche on the December 1 layer in the region suggesting it is either an isolated event or that the layer is just starting to wake up and become a problem.

5-15cm of new snow overnight fell with light to moderate southwest winds, switching to northwest during the day on Thursday. Some new slab formation may have occurred on lee features on most aspects.

The region typically saw 15-25 cm of new snow over the weekend with strong SW winds which formed reactive wind slabs in exposed terrain. Another 15-25 cm of new snow accumulated on Monday and Tuesday which generally appears to have accumulated without any substantial wind. A bit of new snow Wednesday overnight plus moderate to strong winds from the SW shifting to the NW on Thursday are expected to form new wind slabs in exposed terrain. 

Two interfaces from early December may be found down around 60-100 cm. The December 1 interface consists of a thick crust with facets and appears to be most prominent in the south of the region. This layer resulted in a human-triggered avalanche on Tuesday with a surprisingly wide propagation. It is unclear whether this layer is only reactive in isolated areas or it may be waking up as more load is being added to the snowpack. Regardless, this layer should be treated with the upmost respect until more information becomes available, especially in the south of the region. The December 7 interface consists of a thin crust and/or surface hoar which seems to be most prominent in the north of the region. This layer now appears to have gone dormant over the past few days but it had been reactive over the past weekend. 

The lower snowpack is now generally well settled and stable although an old, faceted crust is likely found near the base of the snowpack. 

• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• This avalanche problem is difficult to trigger but if so, consequences are serious.
• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Be alert to conditions that change with elevation and wind exposure.