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, Persistent Slabs and Deep 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: Flurries, up to 5 cm, high wind gradient with elevation, light at 2000 m, strong at 3000 m southwest, freezing level 500 m.
Tuesday: Flurries, up to 10 cm, high wind gradient with elevation, light at 2000 m, strong at 3000 m southwest, alpine high -5, freezing level 1100 m.
Wednesday: Snow overnight then clearing, 10-20 cm, strong southwest wind, alpine high -4, freezing level 1500 m dropping through the day.
Thursday: Sunny, strong southwest wind, alpine high -7, freezing level 700 m with a weak inversion setting up.
Avalanche Summary
Over the weekend we received reports of a couple of natural wind slabs size 1.5, and solar triggered loose snow avalanches size 1-2.
Two human triggered avalanche incidents occurred last Tuesday; a size 1.5 on surface hoar in a northeast facing burn near Glacier National Park (view MIN report here), and a size 2.5 avalanche on an east aspect at treeline in the Lower Holt area, near Golden (view report here).
We have not had any reports of deep persistent slab avalanches on the basal weak layers for over a week.
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 few persistent weak layers exist in the upper to mid snowpack:
- The upper layer, found 40-60 cm down, is a spotty layer of surface hoar at treeline and below.
- The lower layer, found 90-140 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 still 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.
The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers in steep, shallow, rocky areas with a thin to thick snowpack.
Terrain and Travel
- Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
- Dial back your terrain choices if you are seeing more than 20 cm of new snow.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
A bit of new snow and wind 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 weak layer of surface hoar is down 50-100 cm. They are highly variable in form and distribution and have not been associated with recent avalanche activity. 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
Deep Persistent Slabs
A crust buried near the bottom of the snowpack has been responsible for at least one large avalanches in the past week.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 12th, 2021 4:00PM
