Avalanche Forecast
South Rockies
Intense southwest winds are driving wind slab formation at all elevations. Persistent slab activity in deeper in the snowpack still can't be written off.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- If triggered, wind slabs may step down to deeper layers and result in large avalanches.
- Southwest winds will likely form thicker, more sensitive slabs on northeast aspects.
- Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Persistent slab activity has been declining, but potential still exists for large avalanches to be triggered on deeply buried weak layers. Stress on deep weak layers will increase as intense southwest winds continue to load lee areas.
Travel and Terrain Advice
- Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Avalanche Summary
Reports from Saturday showed explosives control in the Castle area producing several Size 2-2.5 storm slabs around 40 cm deep. Ski cutting in the same area produced numerous smaller (Size 1) releases also confined to the recent storm snow.
Looking forward, expect ongoing strong winds to promote lee loading as well as slab formation and reactivity even as snowfall tapers off.
Snowpack Summary
Up to 40 cm of new snow from recent stormy weather has buried both a new layer of feathery surface hoar in sheltered areas as well as sun crust on solar aspects. Moderate to strong winds have been scouring away the new snow on southwest aspects while continuously loading and building wind slabs in lee areas. Beneath the new snow, Previous southwest winds formed wind slabs that are now buried in lee terrain at higher elevations.
Down about 60-80 cm, weak layer of feathery surface hoar crystals and/or sun crust from mid-December is found at treeline and below treeline elevations. Deeper in the snowpack, another weak early-season layer of rain crust and sugary facets exists. This deeper layer is the most concerning persistent weakness in the South Rockies. It is expected to be particularly sensitive to triggering in variable-depth snowpack areas in the alpine. Slabs may still fail on these layers under the weight of a person, a machine, or large wind slab release. Although the snowpack structure is variable across the region, these persistent slab problems are generally widespread. Snowpack depths are across the region are similarly variable, but typically shallower in the east.
Weather Forecast
Tuesday: Mainly cloudy with isolated flurries and a trace of new snow, continuing overnight. Moderate to strong southwest winds. Alpine high temperatures around -7.
Wednesday: Mainly cloudy with continuing scattered flurries and a trace to 5 cm of new snow, continuing overnight. Moderate to strong southwest winds. Freezing level rising to 1600 metres with alpine high temperatures of -3.
Thursday: A mix of sun and cloud with lingering isolated flurries and a trace of new snow. Moderate southwest winds. Freezing level returning to valley bottom with alpine high temperatures of -9.
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Cranking southwest winds will continue to scour away our recent snow into increasingly thick and reactive wind slabs in lee areas. Slabs that form in openings at lower elevations may overlie a layer of touchy surface hoar.