Avalanche Forecast
Issued: Jan 10th, 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
We've seen a drop avalanche activity over the weekend. Even so, watch out for lingering wind slabs and keep in mind the potential for large and destructive persistent slab avalanches.
Summary
Confidence
Weather Forecast
Sunday: Partly cloudy, light southwest wind at 2000 m, high level wind increasing to strong west, freezing level valley bottom.
Monday: Flurries, high level wind strong west, alpine high -8, freezing level 900 m.
Tuesday: Flurries, moderate southwest wind, alpine high -7, freezing level 900 m.
Wednesday: Snow, 5-10 cm, strong southwest wind, alpine high -4, freezing level 1400 m.
Avalanche Summary
Some solar triggered loose snow avalanches up to size 1.5 were reported on Friday and Saturday. The most recent explosive results have been limited to size 1.
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
Variably wind affected surfaces can be found at upper elevations. 40-60 cm of snow sits on facets in the alpine, and a spotty layer of surface hoar that was buried around Christmas treeline and below.
The mid-December crust and/or surface hoar is now down 90-140 cm. Although there have been no new reports of avalanches on this layer in the last few days, it remains possible to trigger where it is well preserved.
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
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Previous snow and wind have created deep pockets of wind slab in lee terrain features at upper elevations. These were very reactive before the weekend and may remain sensitive to human triggers.
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, West, 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 11th, 2021 4:00PM
