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 Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Avalanche hazard will gradually rise over the day and into Tuesday night as new snow and wind form fresh wind slabs at upper elevations.
If you see more than 20 cm by the end of the day, treat avalanche danger as CONSIDERABLE at elevations with wind blowing the snow around.
Summary
Confidence
Weather Forecast
Monday night: Snow, up to 5 cm, moderate to strong southwest wind, freezing level 500 m.
Tuesday: Snow, 5-15 cm, strong southwest wind, alpine high -4, freezing level 1400 m.
Wednesday: Snow overnight 10-20 cm then clearing, strong southwest wind easing to moderate, alpine high -7, freezing level 1200 m.
Thursday: Sunny, light northwest wind, alpine high -7, freezing level 700 m with a weak inversion setting up.
Avalanche Summary
Explosive work on Monday produced wind slabs up to size 1.5. Explosive cornice control work conducted on Saturday produced a size 1.5 cornice which did not trigger a heavily skied slope below, and a vehicle-triggered cornice drop tested a north facing alpine slope below, triggering a size 2 wind slab which did not step down to deeper layers.
Snowpack Summary
Small amounts of new snow fall on wind affected surfaces at upper elevations, surface hoar in wind sheltered areas and a thin crust on solar aspects. Winds are likely redistributing new snow into wind slabs and growing cornices.
A couple of persistent weak layers exist in the upper to mid snowpack:
- The upper layer, found 40-80 cm down, is a spotty layer of surface hoar at treeline and below.
- The lower layer, found 90-150 cm down, is widespread and can present as surface hoar and/or a crust.
Avalanche activity on these layers has dwindled since last week and snowpack tests results have been moderate to hard planar, but not showing propagation. Incoming snowfall in the forecast for this week will add additional load to these layers and may shed some light on whether they will remain a concern.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs are most reactive during their formation.
- Dial back your terrain choices if you are seeing more than 20 cm of new snow.
Problems
Wind Slabs
New snow and strong winds are likely forming fresh wind slabs in leeward terrain features at upper elevations.
Cornices have also been growing. A cornice fall is a large load that can trigger avalanches on the slope below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A couple of weak layers exist in the mid snowpack, buried 40-80 cm and 90-150 cm below the surface. They are highly variable in form and distribution and there has not been any associated avalanche activity in the last few days. Incoming snowfall in the forecast for this week will add additional load to these layers and may shed some light on whether they will remain a concern.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 12th, 2021 4:00PM
