Avalanche Forecast
Issued: Jan 21st, 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
A serious avalanche incident has occurred south of Valemont. Reports of human triggered avalanches indicate the snowpack is very unstable in the region. Stick to well ridden and/or simple terrain.
Summary
Confidence
Avalanche Summary
On Saturday afternoon we received a report of a serious avalanche incident involving people in the Oasis riding area south of Valemont. This avalanche occurred on a north-northeast aspect at 2100m. It was remotely triggered and likely ran on the November facets near the bottom of the snowpack. This large(size 2.5) avalanche had a depth of 80 to 120cm. There were several other reports of human triggered avalanches from nearby areas.
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 of these very large avalanches occurred at upper treeline/lower alpine. Avalanches like these are most likely to be triggered onsteep, shallow and previously undisturbed slopes.
Snowpack Summary
New snow continues to gradually accumulate. 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. 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 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
Saturday Night
Cloudy with up to 5cm of new snow expected. Moderate westerly winds and a low of -8 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 -6 at 1800m.
Monday
Cloudy with flurries bringing up to 10cm of new snow. Strong west winds and a high of -8 at 1800m.
Tuesday
Cloudy with up to 10cm of new snow expected. Moderate to strong northwest winds and a high of -5 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.
- Avoid being on or under sun exposed slopes.
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 steep, shallow previously undisturbed terrain or by first triggering a layer further up in the snowpack.
Remote triggering is a concern for this layer, avoid traveling below steep slopes.
The likelihood of avalanches will increase on sun exposed slopes.
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 of these to trigger are surface hoar layers found 40 to 90cm deep. Be especially cautious around steep convex openings at treeline and below.
Remote triggering is a concern for this layer, avoid traveling below steep slopes.
The likelihood of avalanches will increase on sun exposed slopes.
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.
The likelihood of avalanches will increase on sun exposed slopes.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 22nd, 2023 4:00PM
