While cooling is expected to end the widespread natural avalanche cycle on Monday, the likelihood of human-triggering the persistent slab this week remains less certain.
Caution is still advised on slopes that do not exhibit a surface crust, which can be expected to be largely unaffected by last week's heating.
Warm temps and extreme west winds have developed slab properties in the 10-30cm of recent snow that buries previous slabs. Together, these slabs are up to 60cm thick and have been reactive on two weak layers of facets, surface hoar, or sun crust. Human triggering will remain likely on polar slopes.
This weekend, widespread slab avalanches were observed on steep, solar-exposed terrain entraining wet snow at lower elevations to sz 3. Several cornice failures were also reported at local ski resorts, triggering persistent slabs up to size 2.5.
Avalanche Control:
Saturday - Mount Whymper - 12 shots = 12 slabs sz 2.5-3.5 on the Jan 30 layer
Sunday - Simpson and Wardle - 13 shots = 13 slabs sz 1.5-3 mainly persistent slabs however a few stepped down into midpack or basal layers
10 to 30 cm of snow fell last week on a weak layer of facets, surface hoar, or sun crust. Extreme west winds and warm temperatures have encouraged slab formation (and created solar crusts). Previous slabs, another 10 to 30cm thick sit on a similar weak layer buried January 30.
The mid and lower snowpack is mostly well-settled, though it is heavily facetted in thin snowpack areas. Tree-line snow depths range from 120 cm to 180 cm.
A weak low moved into Alberta Sunday afternoon. Light NE winds will bring upslope cooling overnight . Trace amounts of snow can be expected Monday as the low is pushed west by a ridge forming behind it in Alberta. Less than 5 cm is expected before winds shift back west Tuesday bringing clearing.
