Avalanche Forecast
Issued: Dec 14th, 2022 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.
zryan,
Avalanche Canada
Northerly winds have formed stiff wind slabs in unusual areas and at lower elevations than you might typically expect. These slabs are expected to bond poorly to the underlying crust.
Conservative terrain selection and good travel habits will be essential to manage the developing deep persistent slab problem.
Summary
Confidence
Avalanche Summary
On Monday near Pemberton, a skier-triggered persistent slab avalanche occurred on a northwest aspect in the alpine. The bed surface of this avalanche was reported as a crust with large surface hoar above. Interestingly, this avalanche triggered a size 2 in adjacent terrain, which failed on facets and depth hoar near the ground level. This avalanche is a sign pointing toward a developing deep persistent slab problem in this region.
Observations are limited this time of year. Please keep posting your observations to the MIN; it helps strengthen our information gathering.
Snowpack Summary
In deeper zones at 1900 m, the snowpack is around 100-130 cm, which is low for the middle of December, and it has a weak structure.
Surface: Large surface hoar has been reported in sheltered areas. A crust exists on solar aspects. Boot top powder in deep areas. Same old crusts, facets, and rocks on wind-scoured slopes. Wind slab pockets lee of ridges. Upper-pack: Below last week's new snow is well-developed surface hoar in sheltered areas. The upper part of the snowpack is generally low density and faceting (aka weak).Mid-pack: maybe a crust or two, with a layer of soft facets above. This is likely the primary weak layer.Lower-pack: facets and depth hoar (aka not strong).
Weather Summary
Wednesday night
Clear with cloudy periods. Alpine temperatures drop to a low of -5 °C. Ridge wind 25 km/h occasionally gusting to 55 km/h. Freezing level at valley bottom.
Thursday
Sunny with cloudy periods. Alpine temperatures reach a high of -1 °C. Ridge wind 20 km/h occasionally gusting to 55 km/h from the north. Freezing level at valley bottom.
FridaySunny with cloudy periods and an alpine temperature inversion. Alpine temperatures reach a high of 3 °C. Ridge wind 25 km/h occasionally gusting to 40 km/h from the north. Freezing level rises to 2500 metres.
SaturdaySunny with cloudy periods. Alpine temperatures reach a high of -6 °C. Mostly light ridge wind occasionally gusting to 35 km/h from the southwest. Freezing level at valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid freshly wind loaded terrain features.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- The best and safest riding will be on slopes that have soft snow without any slab properties.
Problems
Wind Slabs
Northerly winds are expected to form fresh wind slabs in lee areas. These slabs are expected to form on southerly aspects and may bond poorly to the underlying crust.
With the sugary, faceted, and weak snowpack wind slabs could step down to the lower snowpack, resulting in larger than expected avalanches.
Aspects: East, South East, South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A slab is starting to form over the very weak basal facets and crusts. Whumpfing and cracking have been observed in many locations and human triggering should be considered possible on any steep slopes where a cohesive slab of snow is found.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 15th, 2022 4:00PM
