Avalanche Forecast

Fair - Forecast snowfall amounts are uncertain on Wednesday

Overview: A zonal weather pattern will continue to bring moisture to the Purcell Mountains, particularly for Wednesday and Thursday. Expect higher freezing levels and greater accumulations further south within the region.Tuesday night: Up to 15cm of snow / Moderate to strong southwesterly winds / Freezing level at about 1000mWednesday: 10-15cm of snow falling late in the day and overnight / Moderate to strong westerly winds / Freezing level rising from surface to about 1600m with the arrival of the system Thursday: 10-25cm of snow / Moderate westerly winds / Freezing level at about 1700mFriday: Flurries / Moderate northwest winds / Freezing level at about 1800m

Over the past week in the Dogtooth Range skiers initiated a cornice fall which triggered a size 2.5 slab avalanche on the slope below. In the same area a size 2 slab was rider triggered from a ridge crest. A size 2 natural slab avalanche was also observed further south in the region. The February 10th interface is thought to have been the culprit in all of these events.More recently, several size 1 natural storm slab avalanches were noted in alpine terrain. They occurred in response to new snow and wind. I would expect more of this with increasing destructive potential with forecast weather.

Anywhere between 15 and 35cm of storm snow overlies weak surface hoar in sheltered areas, a sun crust on solar aspects and thin wind slabs in exposed terrain. On lee slopes these accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Forecast snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 50 and 120cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, destructive avalanches are still a very real concern with recent reports of human triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering has now become unlikely.