Avalanche Forecast
Issued: Jan 18th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Deep Persistent 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.
Summary
Confidence
Moderate
Avalanche Summary
Avalanche activity has gradually slowed down after a widespread natural cycle occurred on Friday and Saturday. There were numerous large (size 2) human triggered avalanches on Sunday, and then on Monday there were fewer human triggered avalanches and they generally were smaller (size 1 to 1.5).
The previous natural cycle produced large to very large avalanches (size 2 to 3.5) at all elevations and aspects on multiple persistent weak layers. Most of the activity was on the two surface hoar layers from January, but there was also activity on the November facets near the bottom of the snowpack. Human triggered avalanches since the storm have primarily been on surface hoar layers buried 40 to 80 cm deep, many occurring in sparely forested terrain. A few large (size 1.5 to 2.5) deep persistent avalanches were triggered with heavy loads on Monday.
Snowpack Summary
New snow is gradually accumulating above settled snow from last week's warm storm. At lower elevations, a rain crust exists down 5 to 25cm, with reported elevations extending up to 2000 m around Nelson, 1700 m around Revelstoke, and 1600 m around Valemount. The snow surface will likely become moist on sun exposed slopes.
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 80 cm deep throughout the Columbias. 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
Wednesday Night
Cloudy with around 5cm of new snow expected. Light to moderate southwest winds and a low of -7 at 1800m.
Thursday
A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light northwest winds and a high of -6 at 1800m.
Friday
A mix of sun and cloud with flurries bringing a few centimeters of new snow. Moderate to strong northwest winds and a high of -7 at 1800m.
Saturday
Cloudy with up to 10cm of new snow. Moderate to strong southwest winds and a high of -6 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.
- Uncertainty is best managed through conservative terrain choices at this time.
Problems
Persistent Slabs
Numerous problematic weak layers exist in the middle of the snowpack, with recent observations suggesting the most likely to trigger are surface hoar layers found 40 to 80 cm deep. Be especially cautious around steep convex openings at treeline and below.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
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 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: All elevations.
Likelihood
Expected Size
Valid until: Jan 19th, 2023 4:00PM
