Avalanche Forecast
Issued: Jan 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Persistent Slabs and Wind Slabs.
trettie,
Avalanche Canada
Continue to make conservative terrain choices and consider the consequences of an avalanche on a chosen slope. You may not see signs of instability but the layers are still there. Avoid shallow, steep, rocky slopes.
Summary
Confidence
Moderate
Avalanche Summary
A few concerning avalanches occurred on Thursday. The first took place in the far north of the region on a southwest facing alpine slope. It was a natural size 3 running on the November facets.
The second was a size 3.5 vehicle remote in the Central Monashees. This avalanche was remotely triggered by a snow cat traveling across a rocky west facing ridgeline. This avalanche also failed on the November facets. The crown was up to 3.5m deep.
The third was another vehicle remote also running on the November facets. This one was in the Selkirks on a south through west facing piece of terrain.
All three of these very large avalanches occurred at upper treeline/lower alpine. In addition to the above mentioned avalanches there were also several skier triggered wind slabs and smaller remotely triggered persistent slab avalanches.
Snowpack Summary
New snow is gradually accumulating above settled snow from last week's warm storm. Southerly winds have pressed exposed terrain and formed wind slabs near ridge tops. At lower elevations, a rain crust exists down 10 to 40cm , with reported elevations extending up to 2000 m around Nelson, 1700 m around Revelstoke, and 1600 m around Valemount.
Two persistent weak layers in the middle of the snowpack remain reactive to human triggering. They are both surface hoar layers that formed in early January and are typically found 40 to 90 cm deep throughout the region. There are also some deeper facet and surface hoar layers that formed in December, but recent snowpack observations suggest they are strengthening.
The bottom of the snowpack is made up of large weak facets buried in late November, which has caused an atypical deep persistent slab problem for this region.
Weather Summary
Friday Night
Mostly cloudy with flurries bringing trace amounts of new snow. Westerly winds decreasing throughout the night to light by early morning. A low of -10 at 1800m.
Saturday
Stormy with up to 10cm of new snow expected. Moderate to strong southwest winds and a high of -4 at 1800m.
Sunday
A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light to moderate northwest winds and a high of -7 at 1800m.
Monday
Cloudy with flurries bringing up to 5cm of new snow. Strong northwest winds and a high of -8 at 1800m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
Problems
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer has most recently been problematic in upper treeline/lower alpine elevations.
Avoid thin and rocky start zones where weak layers sit closer to the surface, riders are most likely to trigger an avalanche on this layer in terrain with shallow or variable snow depths or by first triggering a layer further up in the snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Numerous problematic weak layers exist in the top meter of the snowpack, with recent observations suggesting the most likely to trigger are surface hoar layers found 40 to 90cm deep. Be especially cautious around steep convex openings at treeline and below.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Wind has varied in direction over the past few days. Wind slab could be found on all aspects at treeline and above.
Be aware that wind slabs could step down to deeper layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 21st, 2023 4:00PM
