Avalanche Forecast

Good

Thursday: An incoming storm will build through the day and likely peak some time in the afternoon. 10-15 cm new snow likely by the afternoon. Freezing levels rising briefly to around 1500 m. Winds gusting to 50 km/h from the SW at ridgetop.Friday: The storm looks like it will linger in this area, giving a further 10 cm or so of new snow. Freezing levels should fall back to surface, with treeline temperatures of around -5C. Winds 20-30 km/h from the NW.Saturday: A clearing trend with some sunny breaks. Temperatures falling to around -10C. Winds increasing from the NW in the afternoon at all elevations as arctic air starts to descend from the north.

There was a natural avalanche cycle in this region on Tuesday. Mostly avalanches were running to size 2 in recent storm snow on a variety of aspects and elevations of 1600 m and higher. One exception was a size 3.5 natural avalanche that ran on a steep NW aspect in the alpine and pulled out all the way to ground. As a general trend, the size and severity of avalanches has been greater in the north of the region where there has been more snow.

Snowpack depths in this region average around 140-190 cm. 20-40 cm of recent storm snow has been reported to be poorly bonding to the older snow below. A weak layer consisting of surface hoar crystals, stellar crystals and/or a crust lies around 30-50 cm below the surface. At around 60-90 cm, another weak layer exists. This one was buried early December and comprises surface hoar, facetted snow, and/or a crust. It has shown variable reactivity in recent snowpack tests, but many professional operators are considering it carefully.There are two deeper layers of note. The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas and is now buried 70-110cm below the surface. The October deep persistent weak layer consists of a layer of facets sitting on a crust at the base of the snowpack. This layer is predominantly found on northerly aspects at treeline and in the alpine. The depth of both these layers makes directly triggering an avalanche on them unlikely (maybe a heavy load on a thin spot in steep terrain). Their presence could, however, increase the size of a potential avalanche through step-down.