Avalanche Forecast
Issued: Jan 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Stormy conditions are expected, forming new slabs. The persistent slab problem shouldn't be forgotten yet, particularly around Pine Pass.
Summary
Confidence
Moderate - Uncertainty is due to limitations in the field data. Uncertainty is due to extremely variable snowpack conditions reported through the region.
Weather Forecast
MONDAY NIGHT: Clear skies, 40 to 60 km/h southwest wind, alpine temperature -5 C.
TUESDAY: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the west of the region, 40 to 60 km/h southwest wind, alpine temperature -4 C, freezing level 1300 m.
WEDNESDAY: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the west of the region, 40 km/h west wind, alpine temperature -10 C.
THURSDAY: Mix of sun and cloud, 20 km/h west wind, alpine temperature -9 C.
Avalanche Summary
No recent avalanche activity has been noted. Avalanche activity may increase on Tuesday and Wednesday due to new snow, strong wind, and relatively warm air temperature. Be on your guard during this stormy period.
Snowpack Summary
New snow will accumulate on Tuesday and Wednesday, with the most expected in the west of the region. Storm slabs are expected to rapidly form with relatively mild air temperature. The snow will fall with strong southwest wind, which may form new wind slabs in exposed terrain. This snow will accumulate on previously wind-affected snow in exposed areas, soft snow and perhaps surface hoar in sheltered areas, and a hard melt-freeze crust below about 1600 m.
You may find a couple weak layers of surface hoar in the top 50 cm of the snowpack, as suggested by numerous MINs in the region. This layer is expected to be found in terrain features sheltered from the wind, for example in openings below treeline or at treeline elevations. As the new snow forms slab properties, these layers could become reactive to human traffic.
Around 80 to 100 cm of snow rests above a weak layer buried in early-December which has created a persistent slab avalanche problem and a low probability/high consequence scenario. Depending on location, the buried weak layer is composed of surface hoar and/or a crust/facet combination. Reports suggest that this layer has become dormant in much of the region except for perhaps the Pine Pass area.
Terrain and Travel
- Watch for fresh storm slabs building throughout the day.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Expect slab conditions to change drastically as you move into wind exposed terrain.
- Use small low consequence slopes to test the bond of the new snow.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Storm Slabs
New snow and strong wind are forecast for Tuesday and Wednesday. Storm slabs may form rapidly with relatively mild air temperature. In sheltered areas, the snow may overly weak surface hoar, meaning the snow could slide easily. Strong wind is also forecast, likely forming wind slabs in exposed terrain at higher elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A persistent weak layer exists throughout the region 80 to 100 cm below the surface. In most places it looks like the overlying snow is gaining strength and human triggering is trending towards unlikely. However, areas around the Pine Pass may remain problematic.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 13th, 2021 4:00PM
