Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Regions
South Rockies.
Confidence
Fair
Weather Forecast
High pressure conditions are expected for Thursday before a weak system from the southwest affects the region Thursday night and Friday. On Friday night, cold arctic air will push into the region and will dominate on Saturday.Thursday: A mix of sun and cloud, temperature inversion conditions, ridgetop winds 20-30 W-NWThurs. night/Friday: Mostly cloudy, snow flurries 4-8cm, treeline temperature around -12C, ridgetop winds 10-20 W-NWSaturday: Mostly sunny, treeline temperature around -20C, ridgetop winds 20-30 NE-E
Avalanche Summary
On Tuesday, we received reports of several natural size 1 loose dry avalanches from steeper terrain features, most likely triggered by the sun. Also reported was a size 2 wind slab triggered by explosives near Fernie. Check out the South Rockies Blog for recent photos and insights of what people are seeing out there.
Snowpack Summary
Large cornices loom on ridgelines and threaten the slopes below. Variable winds have transported some of the recent storm snow, building new wind slabs on leeward slopes. A persistent slab 80-120 cm thick sits on a weak interface comprising of facets and a crust. It continues to show sudden planar shears at the interface, and a high degree of sensitivity to human triggers. Wide propagations and remote triggering remain a concern. With forecast sunny periods, solar aspects may see moist snow surfaces which will then form a crust overnight. The deep persistent layer of facets and depth hoar near the base of the snowpack has remained dormant to this point, but may become a concern with additional load and stress on the snowpack like a cornice fall or large avalanche.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.