Avalanche Forecast
Issued: Dec 28th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
jfloyer,
Avalanche Canada
A small chance of triggering a deeper weakness remains. Continue to avoid high consequence terrain to account for this possibility.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Monday night: Dry with clear skies. Cooling temperatures.
Tuesday: 2-5 cm new snow. Treeline temperatures around -14 C. Winds light to moderate southwesterly.Â
Wednesday: 4-8 cm new snow. Treeline temperatures around -6 C. Winds moderate southerly.Â
Thursday: Flurries. Treeline temperatures around -7 C. Winds light southwesterly.
Avalanche Summary
A size 1 wind slab avalanche was reported from an east aspect on Cayoosh on Sunday. Storm slabs and loose dry avalanches were also reported from Chief Pascal on the Duffey and on the Yak/Nak col along the Coquihalla.
A few persistent slab avalanches were reported last week, mostly in the north of the region near the Hurley, but also near Allison Pass. They were triggered by riders, heavy machinery, and naturally. The slabs were generally 60 to 90 cm deep, around 2000 m, and released on the weak layers described in the snowpack summary.
Snowpack Summary
5-15 cm of recent snow has seen some redistribution by wind, resulting in good riding quality on lee aspects in the Coquihalla area, according to the great MIN reports we've received. (If you're going out in the Duffey, please share your observations on the MIN!) Below treeline, recent snow may be sitting over surface hoar.
A hard melt-freeze crust from early December is found around 40 to 120 cm deep in the snowpack. This crust may have weak layers above it, consisting of feathery surface hoar or sugary faceted grains. These weak layers are most prevalent in the north (e.g., Duffey Lake, Hurley) and found to a lesser extent in the south of the region. The snowpack should be treated as suspect anywhere you find either surface hoar or faceted grains above the crust.
The remainder of the snowpack is well-settled in the south of the region. In the north, another melt-freeze crust with associated faceted grains around it may be found near the ground. Without evidence of recent avalanche activity, the layer appears to be dormant at this time.
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Persistent Slabs
Weak layers of surface hoar and/or faceted grains may be found above a hard melt-freeze crust. Recent reports suggest the weak layers may be less prevalent in the south of the region, but still exist in localized pockets.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Wind loaded pockets below ridge crests and rollovers may be reactive to human triggers. Watch for localized reverse-loading on south-facing slopes due to recent northerly winds.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 29th, 2020 4:00PM
