Avalanche Forecast
Issued: Dec 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Storm slabs may remain reactive where they sit over a crust or surface hoar.
Moderate danger below treeline reflects conditions around Golden. Avalanche danger at this elevation will be a step lower in other parts of the region where less than 15 cm of snow sits over the crust.
Summary
Confidence
Weather Forecast
Continued cool temperatures, with a mix of sun, clouds and snow flurries for the next few days as the next weak low pressure moves in Sunday.
Friday Night: Clear with cloudy periods, light and variable winds, alpine low -13C, freezing level valley bottom.
Saturday: Sun and cloud, light and variable winds, alpine High -10C in the north, -7C in the south, freezing level valley bottom.
Sunday: Cloudy with snow flurries, trace Accumulations 0-5cm, light-moderate southerly winds, alpine low -11/ high -8C, freezing level 700 m.
Monday: Cloudy with sunny periods & isolated snow flurries, light to moderate westerly winds, alpine low -11C / high -8C, freezing level 900 m.
Avalanche Summary
Explosive control work at Panorama on Thursday produced numerous size 1 storm slab avalanches on north aspects in the alpine.
Natural, skier and explosive triggered storm slab avalanches up to size 2 were reported throughout the region during the storm Tuesday and Wednesday.
Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Snowpack Summary
10-30 cm of recent snow overlies a rain crust found up to 2450 m in the south of the region and 1800 m in the north. In the north, the recent snow may sit over a weak layer of surface hoar or facets at elevations around treeline where this crust is not found or where it is a very thin lens that formed ontop of the surface hoar. The recent snow does not appear to be bonding well to these old surfaces.
The lower snowpack is characterized by a couple of crusts, the most notable is from a rain event in early November. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.
Terrain and Travel
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Brief periods of sun could quickly initiate natural avalanche activity.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Storm Slabs
Solar triggering of dry snow is possible during sunny periods Saturday. Storm slabs are most likely to remain reactive where they sit over a crust or surface hoar. You can investigate this interface in a number of ways including:
- digging down below the storm snow to have a look at what it is sitting on
- doing a quick hand shear test
- look for signs of instability like shooting cracks and whumping while you travel
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A facet/crust layer from November rains (Nov 5 Crust) sits near the base of the snowpack. This layer has shown signs of recent reactivity with explosive control in shallow rocky locations producing large avalanches.
It is most likely to be triggered by humans in shallow, rocky areas or in a step-down from a smaller avalanche.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 12th, 2020 4:00PM
