Avalanche Forecast
Issued: Jan 17th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
jleblanc,
Avalanche Canada
Conditions may be improving, but be mindful of isolated pockets of winds slabs that may poorly bond to the underlying snow.
Summary
Confidence
High - We have a good understanding of the snowpack structure and confidence in the weather forecast
Weather Forecast
MONDAY NIGHT: Snow 5-10 cm, treeline high around -3 C, strong southwest wind, freezing level around 1500 m.
TUESDAY: Light snow up to 5 cm, light variable wind, treeline high around -10 C, freezing level returning to valley bottom.
WEDNESDAY: Clearing, light southwest wind, treeline high around -12 C, freezing level returning to valley bottom.
THURSDAY: Snow up to 5 cm, moderate southwest wind, treeline high around -4 C, freezing level rising to 1000 m.
Avalanche Summary
A near-miss happened this weekend on Tombstone mountain when a rider triggered a large persistent slab and got completely buried. Luckily, the airbag helped keep the victim's head above the snow. This evidence suggests the deep persistent slab problem is still a concern in the region.
Thursday, three very large avalanches were reported from this region. The avalanches appear to have failed on the early December crust and showed wide propagation. They occurred on southwest to southeast aspects and were naturally triggered in response to rising temperatures and solar radiation. These avalanches follow a previous sporadic pattern of very large avalanches that have been reported from this region and neighbouring regions over the last couple of weeks.Â
Snowpack Summary
Fresh dry snow can still remain at upper elevation but will be most likely wind affected. Around 2000 m and below, a crust is now capping the dense 15 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Under it, the snowpack consists of a variety of old surfaces, including soft snow in sheltered areas and wind slabs in exposed and open areas, which formed over the past few days.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 100-270 cm. This layer appeared to have "waken up" in response to warm temperatures and solar radiation on Thursday Jan 13, when at least three very large avalanches were reported on this layer. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
Terrain and Travel
- Wind slabs may be poorly bonded to the underlying crust.
- Watch for areas of hard wind slab on alpine features.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Wind Slabs
Fresh and soft slabs will likely develop on exposed slopes at higher elevations with the forecasted winds and snowfalls. While these slabs may be thin, they could be poorly bonded to the underlying snow, so be extra cautious in lee terrain and convex rolls.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
A persistent slab problem formed by a crust down 100-270 cm has created a low likelihood, high consequence scenario that is difficult to forecast. There has been an increase of avalanche reports on this deep layer recently. This problem is likely to be triggered on steep, rocky slopes with a shallow or thin-to-thick snowpack. The same feature or path can slide repeatedly when the persistent weak layer is reloaded with new snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 18th, 2022 4:00PM
