Conditions are more complicated than what meets the eye. Fresh, reactive wind slabs are expected to form at upper elevations. Riders may be drawn to more sheltered areas around treeline to avoid these wind slabs, but should consider that this is where the persistent slab problem has been most problematic to date. Keep your terrain choices conservative and don't let good riding lure you into steeper terrain.
Westerly winds are expected to redistribute the loose, powdery surface snow into fresh and reactive wind slabs in the alpine and open areas at treeline.
It is possible small avalanches in the upper snowpack could trigger deeper weak layers, creating a larger then expected avalanche.
Buried layers of surface hoar and facets have been reactive to human triggers in recent days. The most reactivity has been observed in shaded areas at treeline, where surface hoar may be preserved, and in wind loaded areas at upper elevations, where a cohesive slab has been formed.
Observations on this layer are currently limited. In times of uncertainty such as this, our best defence is to keep terrain choices conservative and reduce your exposure to avalanche terrain where possible.
On Sunday, a MIN report from Tunnel Creek reported reactivity in a snowpack test on the Mid-November layer on a south aspect. In this area, the layer presented as facets on a crust. They also observed a large natural avalanche on a west-facing slope at treeline. (Thanks for the report- ESPETERS10)
On Saturday, a small (size 1.5) skier triggered persistent slab avalanche occurred on an east-facing slope at treeline.
Numerous reports of small loose dry avalanches (sluffing) have been reported within the recently fallen low-density surface snow.
We have very few eyes out there. If you do get out please consider reporting in the MIN.
Overnight and throughout the day 5-15 cm of new snow is expected. This new snow will add to the ~25 cm of storm snow that fell early in the weekend. In wind-affected terrain, westerly winds are expected to redistribute this new snow into fresh wind slabs. In sheltered terrain, cold temperatures will likely maintain low-density, powdery snow.
The middle of the snowpack consists of weak sugary layers of facets and surface hoar. A widespread rain crust remains near the ground at treeline and below treeline.
At treeline, snowpack depths vary from 120-200 cm.
Monday night
Cloudy with snowfall, 5-10 cm of accumulation expected. Westerly winds 20-35 km/h at ridgetop. Treeline temperatures drop to -13 C.
Tuesday
Cloudy with snowfall, generally ~5 cm accumulation, up to 15 cm in the far south of the region. Westerly winds 25-40 km/h at ridgetop. Treeline temperatures reach a high of -10 C.
WednesdayCloudy with light snowfall, up to 4 cm of accumulation. Westerly winds 15-30 km/h at ridgetop. Treeline temperatures reach a high of -8 C.
ThursdayMore of the same! Cloudy with snowfall, up to 5 cm of accumulation. Westerly winds 25-45 km/h at ridgetop. Treeline temperatures reach a high of -6 C.
More details can be found in the Mountain Weather Forecast.
