Avalanche Forecast
Issued: Dec 6th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Fresh and reactive wind slabs may exist at treeline and above. Watch and feel for signs of instability such as whumpfing, cracking, and recent avalanches.
Concern remains for the persistent weak layers near the base of the snowpack where a small avalanche could possibly 'step down' initiating a larger one. With uncertainty, the best approach is choosing conservative terrain.
Summary
Confidence
Avalanche Summary
Explosive control on Sunday produced several small (size 1-1.5) persistent slab avalanches from North and Northwest facing treeline. These avalanches failed on the Mid-November surface hoar layer.
On Saturday, a small (size 1) skier triggered persistent slab avalanche occurred on a northwest aspect at treeline. A larger (size 2) natural slab avalanche was also observed from a distance on an east-facing alpine slope.
Last week, a small (size 1) natural persistent slab avalanche was observed at treeline on a steep, south-facing road bank. It failed on the sugary, faceted layer 25 cm deep.
We have very few eyes out there. If you do get out please consider reporting in the MIN.
Snowpack Summary
Up to 5 cm of new low-density snow fell on Tuesday. Consistent and strong westerly winds may have been enough to blow around the new and old snow, forming fresh wind slabs in the alpine and treeline. In exposed terrain, some slopes have been scoured back to rock and in sheltered areas, 20-60 cm overlies a generally weak and sugary (faceted) lower snowpack. The prolonged cold temperatures have weakened the generally thin snowpack, promoting faceting as a whole. A buried layer of surface hoar sits 25-60 cm deep and remains a layer of concern.
The overall height of snow is highly variable throughout the region with around 40-150 cm in the alpine.
Weather Summary
Tuesday Night
Cloudy with light snowfall, less than 5 cm of accumulation expected. Strong to extreme westerly winds at ridgetop. Temperatures steady at -15 C.
Wednesday
New snow up to 5 cm of accumulation is expected. Moderate to strong ridgetop wind from the southwest and temperatures slightly warmer near -12 C.
ThursdayMix of sun and cloud and dribs and drabs for the remainder of the work week. Moderate ridgetop wind from the south-southwest and a daytime high of -10 C. Freezing levels 700 m.
FridayMix of sun and cloud. Southwesterly winds 30-60 km/h at ridgetop. Temperatures reach a daytime high of -8 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Strong westerly winds may redistribute powdery surface snow into fresh and reactive wind slabs in the alpine and open areas at treeline.
These slabs likely overlay a weak, sugary lower snowpack. If triggered, small avalanches may trigger a bigger avalanche by 'stepping down' to these weak crystals.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Buried layers of surface hoar and facets have been reactive to human triggering in recent days. The most reactivity has been observed in sheltered areas at treeline, where surface hoar may be preserved, and in wind loaded areas at upper elevations, where a cohesive slab has been formed.
Observations on this layer are currently limited. In times of uncertainty such as this, our best defense is to keep terrain choices conservative and reduce your exposure to avalanche terrain where possible.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 7th, 2022 4:00PM
