Avalanche Forecast

Fair - Freezing levels are uncertain

As the current storm pattern tapers-off, a warmer southwest air mass will over-ride the cooler remnant arctic air. The result will be light rain at ridge top elevations and freezing rain below treeline. A clearing pattern will evolve throughout Tuesday and will persist until Thursday as a warm, dry ridge of high pressure develops. Valley temperatures will remain below freezing for the forecast period; however, an inversion is forecast until Thursday with alpine temperatures exceeding zero degrees celcius each day. Ridgetop winds are forecast to peak at about 60km/h from the west on Tuesday morning, and then taper to about 20 km/h from the northwest for the rest of the period.

At the time of publishing this bulletin, observations were extremely limited. In the wake of Sunday night's storm, I'm sure there was widespread storm slab activity with many avalanches stepping down to the mid-December crust/ surface hoar interface. With further loading on Monday (and subsequent warming), I'm sure we'll see ongoing large and destructive storm and persistent slab avalanche activity.

Up to 40cm of new snow fell on Sunday night, with moderate southwest winds shifting these accumulations into deeper deposits in lee terrain. With more wind, snow and warming on the way, this potent new storm slab will likely remain sensitive to light triggers. The new snow overlies a variety of old surfaces which include heavily wind-affected surfaces in exposed locations, and faceted powder and buried surface hoar in sheltered terrain. Up to 100 cm below the surface, you'll likely find a touchy weak layer of surface hoar sitting on a thick rain crust. This widespread persistent weakness exists at all elevation bands, and continues to be the primary layer of concern for the region. With the current storm loading pattern, I expect this layer to increase in reactivity with the potential for large and destructive avalanches. At the base of the snowpack, a crust/facet combo appears to have gone dormant for the time being.