Avalanche Forecast
Issued: Jan 9th, 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
Wind slabs will be the most apparent avalanche problem you encounter but keep the potential for persistent slab avalanches in your mind. Avalanche danger may be improving as the likelihood of triggering diminishes but if you're unlucky enough to do so, consequences can be high.
Summary
Confidence
Weather Forecast
Saturday night: Partly cloudy, light southwest wind at 2000 m, high level wind increasing to moderate west, freezing level valley bottom.
Sunday: Mix of sun and cloud, light southwest wind at 2000 m, high level wind increasing to strong west, alpine high -9, freezing level 600 m.
Monday: Mostly cloudy, light southwest wind at 2000 m, high level wind strong west, alpine high -8, freezing level 1000 m.
Tuesday: Flurries, light southwest wind at 2000 m, high level wind strong west, alpine high -6, freezing level 1200 m.
Avalanche Summary
Some solar triggered loose snow avalanches up to size 1.5 were reported on Friday afternoon. A few natural, human and explosive triggered wind slabs size 1-2 were reported across the region in the latter part of the week.
Two human triggered avalanche incidents occurred on 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). Thankfully there were no injuries.
A notable avalanche from the natural storm cycle that occurred last weekend include a natural size 2.5 deep persistent slab avalanche reported on a north aspect at 2500 m near Invermere.
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.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
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, and may still triggerable by humans in areas where it exists.
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 10th, 2021 4:00PM
