Avalanche Forecast
Issued: Dec 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.
dsaly,
Avalanche Canada
Southwest winds are blowing soft snow into fresh wind slabs in lee terrain features at upper elevations. Use caution moving into wind affected terrain.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
WEDNESDAY NIGHT - A mix of sun and cloud with isolated flurries, 5-10 cm / southwest wind, 25-55 km/h / alpine high temperature near -7Â
THURSDAY - Mainly cloudy with isolated flurries. 5-10 cm / west wind, 20-50 km/h / alpine high temperature near -6
FRIDAY - Mainly cloudy with scattered flurries / southwest wind, 20-40 km/h / alpine high temperature near -8
SATURDAY - Snow, 10-20 cm / southwest wind, 25-55 km/h / alpine high temperature near -7
Avalanche Summary
Moderate southwest winds may form fresh windslabs that could be reactive to human triggers at upper elevations. Check out this MIN report from the KHMR backcountry - poor bonding between the new snow and old surface resulting in sluffing and loose, dry avalanches, and small windslabs in steep rocky terrain.
Avalanche control work on Tuesday produced a few small (size 1) storm slab and dry loose avalanches.
A MIN report from the Clamshell near Golden reported a natural size 2.5 avalanche last Wednesday (Dec 9). This avalanche appears to have run on a weak layer roughly 40 cm below the surface, which seems to be an isolated problem in this area.
Snowpack Summary
10-35 cm of snow overlies a rain crust found up to 2400 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. South-southwesterly winds are creating new, small cornices and wind slabs on lee slopes. The recent snow may not be bonding well to older surfaces. There have also been some reports of an isolated weak layer 40 cm below the surface around Golden.
The lower snowpack is characterized by a couple of crusts, the most notable is from a rain event in early November that is 50 to 100 cm deep. 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
- Investigate the bond of the recent snow
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
Increasing winds impacting 10-30 cm of soft surface snow may blow into unstable slabs. In certain areas this snow may be poorly bonded to underlying layers of surface hoar and/or crusts. The problem is more likely found in northern parts of the region (e.g. Golden).
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A facet/crust layer from early November 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 17th, 2020 4:00PM
