Avalanche Forecast

TUESDAY NIGHT: Cloudy with flurries / 2-10 cm snow with higher rates focused around Allison Pass and the Coquihialla / light to moderate northwest wind / ridgeline temperature low -15 / freezing level valley bottom

WEDNESDAY: Mostly sunny with scattered clouds / light northwest wind at most elevations with moderate north wind at the highest elevations / ridgeline temperature high -6 / freezing level around 600 m

THURSDAY: Scattered clouds and incoming flurries beginning to accumulate overnight / moderate southeasterly wind / ridgeline temperature high -4 / freezing level around 600 m

FRIDAY: Snow, 5-15 cm / moderate southwesterly wind / ridgeline temperature high -4 / freezing level rising to 1000 m

More evidence of recent large size 2-3.5 natural wind slab avalanches were reported on Monday. Several dry loose avalanches size 1-2, entraining 10-25 cm recent snow and running on top of windslab, were observed in steep terrain.

On Sunday a size 3 natural avalanche was observed on a southwest facing alpine feature in the north of the region. MIN reports from Sunday detail a lot of good skiing in wind sheltered terrain.

Recent wind slab formations are widespread in the region, with small (size 1.5) wind slabs triggered with ski cutting on wind loaded slopes in the Coquihalla on Friday and Saturday. Check out this MIN report for a great example of layered/obscured wind slabs reactive to skier triggering in the south of the region. Another MIN detailing an avalanche involvement in the north of the region gives a clear picture of hazards perched on alpine features.

A notable size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass February 8th. This occurred on a southwest aspect at 2400 m. It was described as a hard wind slab formed over our facet layer from late January.

10-25 cm low density snow overlies a widespread variety of wind affected surfaces, and in sheltered and north-facing areas 20 cm (north of the region) to 60 cm (south of the region) of faceting older snow. On solar aspects, a thin sun crust may be found below fresh or recently wind transported snow, potentially contributing to the reactivity of new slabs on sun-exposed aspects.

Previous to Monday's snow, region-wide northeast winds formed many new wind slabs across exposed higher elevation terrain. Winds have not been consistent, so don’t be surprised to find reactive, potentially layered or buried slabs on a wide range of aspects as you approach wind-exposed terrain.

Persistent weak layers of concern below this storm snow vary by location in the region. In the south, the primary feature, found at treeline and below in the Allison Pass area, is a melt-freeze crust from mid-January, about 50 cm deep. Although this layer is present (twice as deep) in the Coquihalla snowpack, no persistent weak layers are currently considered problematic in that area.

In the north, many of the recent wind slab formations discussed above have been reactive to skier triggering on early February interfaces of surface hoar (think shaded aspects), and may also exist over a thin sun crust from the same period (think solar aspects). Another older (January 24), slightly deeper, widespread layer of faceted snow remains a concern in shallow or variable snowpack depth locations in the alpine. 

Also In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports have suggested that this layer is unreactive and gaining strength, however ongoing cold temperatures may currently be weakening the snow around it in thin snowpack areas.

• Recent new snow may be hiding windslabs that were easily visible before the snow fell.
• Avoid freshly wind loaded terrain features.
• Watch for areas of hard wind slab on alpine features.
• Be aware of highly variable recent wind loading patterns.
• Closely monitor how the new snow is bonding to the old surface.