Avalanche Forecast
South Columbia
There is uncertainty in forecast snowfall amounts Thursday into Friday. The higher end of estimates will be concentrated in the south of the region.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use ridges or ribs to avoid pockets of wind loaded snow.
- Be cautious as you transition into wind affected terrain.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
A weak layer of surface hoar buried 50-80 cm deep has potential to produce large avalanches where the overlying snow has settled into a cohesive slab.
Travel and Terrain Advice
- Watch for signs of slab formation, such as wind effect, whumpfing, or shooting cracks.
- Buried surface hoar is more likely to be preserved in sheltered openings at and below tree line.
Avalanche Summary
A report from just northeast of Nakusp on Monday shows a size 2 persistent slab release on a north aspect at 1800 metres. Another report from Sunday showed a skier-triggered Size 1 persistent slab releasing from a north aspect at 2200 metres.
Snowpack Summary
Last week's storm brought 50-80 cm of new snow to the region. Predominantly northerly winds have since redistributed this storm snow into wind slabs at higher elevations. In sheltered areas cold temperatures have inhibited slab formation. The storm snow lies over a variety of old surfaces, including surface hoar (weak, feather-like crystals), sun crust, and sugary facets. The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, such as sheltered areas at and below treeline or sheltered northerly aspects in the alpine. Recent snowpack tests show wide ranging reactivity on this weak layer but suggest that it may be most reactive on northerly aspects.
A rain crust that formed in late November is now buried 90-120cm deep. Recent evidence from adjacent regions suggests it may be reactive in steep, variably loaded terrain features in the alpine.
Weather Forecast
THURSDAY: Flurries, accumulation 5-10cm / Wind light south / Alpine temperature -10
FRIDAY: Isolated flurries, accumulation 5-10cm / Wind light to moderate southeast / Alpine temperature -10
SATURDAY: Mix of sun and cloud / Wind light west / Alpine temperature -11
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Recent northwest winds shifting to west and southwest have formed windslabs in the lee of terrain features.