Avalanche Forecast
Issued: Dec 12th, 2021 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.
ghelgeson,
Avalanche Canada
If you're heading out into the cold you're going to want to seek out wind sheltered terrain where you can avoid fresh wind slabs.
Summary
Confidence
Weather Forecast
Brrrrrrr!
SUNDAY NIGHT: Low temperature around -26 C, light to moderate outflow winds out of the northeast, most prominent at lower elevation, no snow expected.
MONDAY: Broken clearing to scattered cloud cover in the late afternoon, daytime high temperature around - 20 C, light variable wind, no new snow expected.
TUESDAY: Clear skies at dawn with cloud cover increasing after lunch, daytime high around -16, light to moderate south/southwest wind, no snow expected.
WEDNESDAY: Broken cloud cover, wind light southwest in the early morning steadily increasing to moderate west southwest in the afternoon, light flurries possible after lunch.
Avalanche Summary
Explosive control earlier in the month produced many large avalanches that failed on the weak sugary crystals at the bottom of the snowpack. These avalanches ran full path.
On December 1, a size 2.5 avalanche was remotely triggered by a recreational group on Log Cabin. This avalanche likely failed on the weak, sugary snow at the bottom of the snowpack.
Natural avalanche activity and human triggered avalanches will be most likely in wind-loaded features anywhere recent winds have redistributed the snow. Triggering the deep layer (see the December 1 avalanche described above) is most likely to occur in shallow areas or where the snowpack variable in depth with a mix of shallow and deep zones.
Snowpack Summary
Low density snow from the last storm is being redistributed by winds that were at first southerly then switched to north, then northeasterly, now northwesterly. Old wind slabs on northerly aspects are likely becoming less sensitive, but expect new wind slabs on south, southwest and southeast aspects. Snow quality will be best in sheltered areas, which is also where you are least likely to find wind slab problems.
The middle snowpack is supportive to travel but snow depth still varies greatly with aspect and elevation.
A layer of weak, sugary snow at the base of the snowpack has been observed in most areas. This layer was reactive earlier in December, and it might still be possible to trigger this deeply buried layer in shallow snowpack areas or if a cornice fall or surface avalanche impacts a slope. If triggered, this basal layer could produce large avalanches. This sugary layer will likely become weaker in the coming days with increasingly cold temperatures potentially making it increasingly sensitive to triggering.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Approach lee and cross-loaded slopes with caution.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
Problems
Wind Slabs
Wind slabs on south facing aspects are the most likely to be remain sensitive to human triggering Monday. Moderate to strong wind out of the west/northwest began to pickup Saturday night and continued into Sunday. The cold temperatures will likely dampen their sensitivity, but you're probably not going to find riding conditions to be very good in wind exposed terrain.
Aspects: North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
This layer is becoming more deeply buried and somewhat harder to trigger. But it would likely result in a large avalanche if you tickle it from the wrong spot. Most likely trigger points are areas where the snowpack is shallow or variable so avoid fat to thin transitions and stick to places where the snowpack is deep. Remote triggering is possible and a cornice fall or surface avalanche could set off a deeper slide so be aware of your overhead exposure. Decreasing temperatures will initially make it harder to trigger this problem but if the cold persists, the failure layer will become weaker and we may eventually see sensitivity creeping up again in the coming days
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 13th, 2021 4:00PM
