The deep mid-Dec layer remains reactive and there have been several avalanches on this layer in the last few days. Use a conservative approach and assess conditions before committing to big terrain features.
Summary
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The first warm front should reach the region on Friday afternoon. Freezing levels are forecast to climb to around 1500m on Friday afternoon. 10-15mm is expected for Friday night into Saturday morning with strong SW winds in the alpine. A lull in the storm is expected during the day on Saturday before the second wave arrives Saturday evening. On Saturday, freezing levels are forecast to rise to around 2500m. Another 10-15mm are possible Saturday night into Sunday but unfortunately this likely means rain into alpine elevations. The storm system is forecast to end on Sunday but freezing levels will remain over 2500m for several more days.
Avalanche Summary
On Wednesday, skiers triggered a few persistent slab avalanches size 1-1.5 on the mid-Jan weak layer. These were typically 20-30cm thick and occurred between 2000 and 2300m elevation. Explosives triggered several deep persistent slabs up to size 3 on the deeper mid-Dec layer. These were typically 40-100cm thick. On Tuesday, one natural avalanche was reported. A cornice broke off and triggered a deep slab avalanche on the mid-Dec layer. Three skier-triggered avalanches were also reported and these all released on the mid-Dec surface hoar layer. Depths varied from 30cm to 100cm with typical values around 70cm. Natural avalanche activity is generally not expected on Friday. Human-triggering remains a concern in wind loaded areas and steep terrain features, especially where surface hoar underlies the recent storm snow.
Snowpack Summary
Around 30cm of snow sits on the mid-Jan surface hoar layer. In many places the surface hoar sits above a thin crust that can be found up to about 1900m on north aspects and all the way to ridgeline on south aspects. Strong SW winds during the storm loaded leeward features and the persistent slab may be 50-60cm thick in wind loaded areas (typically north through east aspects). A deeper crust/surface hoar combo buried in mid-December continues to be a concern. This layer can typically be found down 70-100cm. The reactivity of this deep persistent weak layer appears to have become isolated but still has the potential for large, destructive avalanches in some areas. The layer has been the most reactive at and just below treeline.
rbuhler,
Avalanche Canada
