Avalanche Forecast
Issued: Jan 16th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
If you decide to brave the cold Friday, low elevation trees are your best chance at avoiding windslabs and finding soft snow. The short trip from the car is an added bonus on a chilly day.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
Thursday night: Few clouds with isolated flurries bringing a trace of new snow. Light south winds. Alpine temperatures around -28 C.
Friday: Mix of sun and cloud. Light south to southwest winds. Alpine temperatures around -26 C.
Saturday: Mix of sun and cloud with isolated flurries bringing up to 5 cm of new snow. Strong southeast to southwest winds. Alpine temperatures around -18 C.
Sunday: Mix of sun and cloud with isolated flurries bringing up to 5 cm of new snow. Moderate southeast to southwest winds, strong at ridgetop. Alpine temperatures around -15 C.
Avalanche Summary
On Wednesday, we received reports of skier triggered windslab avalanches size 1.5-2.5 around treeline. Crown depths were around 1 m, and they ran on a surface hoar layer buried by the previous storm on January 10th.Â
Reports from the Bulkley Valley Monday detail natural windslab and persistent slab avalanche activity, size 2.5-3 on aspects lee to previous strong outflow winds. The persistent slab avalanches are suspected to be isolated incidents of avalanches running on the deep November crust.
Snowpack Summary
North to east aspects in the alpine have been wind scoured, with isolated hard windslab in lees. Wind effect also observed in open areas at treeline and below, where wind loaded pockets have been observed to exceed 1 m in depth. Snow in protected areas is unconsolidated and well preserved by the cold temperatures.Â
Recent reports indicate that this wind affected surface snow overlies a layer of surface hoar in many areas, particularly at treeline. This layer has been associated with recent skier triggered avalanche activity. Deeper in the snowpack, another couple of surface hoar layers are currently buried about 80-120 cm below the surface in sheltered areas around treeline. There have been no reports of avalanche activity associated with them for a few weeks, during which several storm slab avalanche cycles have tested their potential for step-downs.
A deep crust from mid November lurks at the base of the snowpack. A couple of recent large avalanches are suspected to have run on this layer in isolated incidents high in the alpine.
Terrain and Travel
- Sheltered low elevation terrain will likely offer the best and safest riding today.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Wind Slabs
Previous strong outflow winds have blown snow into wind slabs extensively in the alpine and in open areas at treeline and below, where wind loaded pockets have been observed to exceed 1 m in depth. While reactivity may be diminishing in the cold temperatures, in places where windslabs sit on surface hoar the problem will likely remain well preserved.
Aspects: South East, South, South West, West, North West.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A deep crust from mid November lurks at the base of the snowpack. There is uncertainty around its prevalence as an active avalanche problem as opposed to isolated incidents of large naturals in lee or cross loaded extreme alpine terrain. Human or even vehicle triggering at this depth is difficult, but can occur from shallow, rocky areas and propagate out to where the snow is deeper. If triggered these are very large, high consequence avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 17th, 2020 5:00PM
