Avalanche Forecast

Moderate - Uncertainty is due to the limited number of field observations.

A break in the weather is expected on Wednesday before the next system arrives overnight bringing light snowfall for Thursday. 

Tuesday night: Periods of light snowfall 3-6 cm, light variable wind, treeline temperature dropping to around -24 °C. 

Wednesday: A mix of sun and cloud, light N wind, treeline high around -20 °C. 

Thursday: Snowfall 4-8 cm, moderate to strong SW wind, treeline high around -12 °C. 

Friday: Snowfall 5-10 cm, moderate to strong SW wind, treeline high around -6 °C. 

On Monday and Tuesday, explosives were triggering storm slabs up to size 2. Ski cutting was triggering size 1 storm slabs and loose dry avalanches on steep slopes. 

On Sunday, a size 2.5 persistent slab avalanche was triggered on an E aspect at treeline. This MIN post goes into more details and has some great photos showing the nature of the problem and the type of terrain where this problem seems most prevalent. On last Friday, a size 2.5 persistent slab avalanche was reported on a north aspect at 2000 m elevation. This failed on the early December weak layer down 100-175 cm. 

On Wednesday, recently formed storm slabs are expected to remain reactive to human triggering. These new slabs may sit on a weak interface which may result in them persisting longer than normal. The early-Dec persistent slab problem remains a serious concern and the weight of the new snow may have increased the reactivity of these deeper layers. Smaller storm slab avalanches also have the potential to step down to deeper layers resulting in very large avalanches. 

The region typically received 25-30 cm of new snow from the recent storm. This new storm snow buried a variable snow surface which may be weak and includes widespread facets, wind affected surfaces, and/or surface hoar in sheltered areas. The new snowfall was accompanied by moderate to strong winds at higher elevations and the new storm slabs are expected to be most reactive in wind loaded areas in the alpine. 

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-200 cm. Activity on this layer has been sporadic, but most recently produced large avalanches on January 2 and December 31. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.