Avalanche Forecast

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Saturday night: Cloudy with flurries bringing 5-10 cm of new snow, continuing into the morning. Moderate to strong southwest winds shifting west.

Sunday: Cloudy with continuing scattered flurries and about 5 more cm of new snow, easing overnight. Moderate to strong west winds shifting northwest and easing. Alpine high temperatures around -7 with freezing levels rising to 1000 metres.

Monday: A mix of sun and cloud. Light northwest winds shifting southwest and increasing overnight. Alpine high temperatures around -9.

Tuesday: Cloudy with flurries bringing about 5 cm of new snow. Strong southwest winds shifting west and easing overnight.

Observations from the neighbouring North Columbias may serve to illustrate the kind of activity that likely took place in southern parts of the region midweek. Here, observations show many storm and wind slab releases generally in the size 1.5-2.5 range with several reaching up to size 3. In the Trans-Canada corridor, a size 4 (VERY LARGE) avalanche ran on Mt. Laurie. Activity was likely less pronounced in the north of the Cariboos, which saw closer to 15 cm of new snow.

Persistent slab releases have not figured too prominently in reports thus far, but observations are still limited and the few that have been reported are notable. Check out these MIN reports from the Dore River and the Gorge (near Revelstoke) for an example of the isolated deep releases we're concerned about.

Looking forward to Sunday, it's worth continuing to give wind slabs a wide berth as you approach wind affected terrain, and to remain suspicious of steeper sheltered slopes where storm snow may have slabbed up over a layer of surface hoar. Using small test slopes to investigate the bond of the storm snow is a good plan, but be cautious about extending your observations to more committing terrain.

Forecast new snow will also add to (and obscure) our wind slab problem, while adding just a bit more load to our buried surface hoar. In the north of the region this new load could be critical.

Since field observations in this region are limited, please consider submitting your observations to the Mountain Information Network. 

15-40 cm of snow fell in the region during Tuesday's storm, with accumulations greatly favouring the south of the region. In exposed areas, recent elevated winds have been redistributing new snow into wind slabs and adding to cornices. This layer of storm snow covers yet more wind affected surfaces at upper elevations, but also surface hoar in wind sheltered areas and a thin crust on solar aspects. 

In most places, the storm snow is probably forming a good bond with the previous surface. Exceptions are likely in areas harbouring surface hoar. Think of shaded upper below treeline and lower treeline areas, above where any thick surface crust exists and below more wind-affected elevations. It's mainly in the south of the region where enough storm snow sits above this layer to pose a real threat, but the north of the region should catch up during the incoming storm through Sunday afternoon.

A couple of older persistent weak layers exist in the mid to lower snowpack. The distribution of these layers are variable, but follows a similar pattern to the layer discussed above. The upper layer (from late December, down about 70-120 cm) is spotty surface hoar at shaded treeline and below and the lower layer (from early December, now likely closer to 150 cm deep) may present as decomposing surface hoar but more likely as a crust/facet combination. It was most prevalent in areas near Valemount. 

Aside from last week's storm producing isolated releases on these deeper layers (see the avalanche summary for details), avalanche activity at these depths has been on a downward trend for a couple of weeks. Snowpack tests have been giving increasingly resistant results, but in isolated tests the upper layer still shows an energetic fracture character. Observations from adjacent regions show the lower layer is largely unreactive, but remains a prominent feature in the lower snowpack.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
• When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.