Avalanche forecast

South Columbia

Feb 24 – 25, 2021Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Ease into terrain cautiously on Wednesday. Start small and look for signs of instability. Be mindful that sunshine can have a powerful effect on stability - and your desire to push into aggressive terrain.

Avalanche danger in the Monashees may be one step lower at all elevations.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2

    40-80 cm of recent storm sits overtop a thick layer of weak, sugary facets. In the Monashees, this interface appears to be bonding well, while reactivity may persist longer in the Selkirks. Human triggering is most likely in wind loaded features.

    Cornices have likely experienced rapid growth with recent strong westerly winds. Fresh, unsupported tabs may weaken in the sun Wednesday. Tabs that break off can act as triggers on slopes below.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

TUESDAY NIGHT: Partly cloudy, light northwest wind, freezing level valley bottom.

WEDNESDAY: Sunny, light westerly wind increasing in the evening, freezing level 1000 m.

THURSDAY: 5-15 cm of new snow, strong southwest overnight wind easing to moderate, freezing level 1200 m.

FRIDAY: 5-15 cm of new snow, light southwest wind, freezing level 1000 m.

Avalanche Summary

In the Monashees, where snowfall started earliest and accumulated the highest amounts in the region, natural activity up to size 2 was surprisingly limited, peaking over the weekend. Strom slabs have since become more stubborn to trigger, as described in these MIN reports from Monday here and here. 

The Highway 1 corridor through the Selkirks (eastern ranges of the region) were the hotspot for storm activity this cycle, with widespread natural wind and storm slab avalanches size 2-3 and explosive triggered size 3-4, many running to valley bottom. Activity was ongoing as of Monday night in neighboring Glacier National Park.

Farther south in the Selkirks, natural and explosive triggered size 1.5-2 storm slabs were reported on Monday and storm slabs up to size 1 were reactive to skier traffic.

Persistent slab activity has been largely absent from reports through the storm throughout the region.

Snowpack Summary

Recent snowfall amounts of 40-80 cm have been highest in the north and lowest in the south of the region. The recent snow has been blown around by previous strong to extreme westerly winds, forming thick slabs in lee features at upper elevations.

The recent snow sits on old, facetted and/or extensively wind affected snow that sat on the surface during the extended cold, windy drought period. There is uncertainty around how long it will take for this interface to bond but reports from the Monashees have indicated a positive trend already.

We've now got 80 to 160 cm of snow above the late January persistent weak layer which is composed of surface hoar in openings in the trees and/ or a crust on steep solar aspects. An absence of step-downs to this layer in the most recent storm cycle indicate that is has likely healed.

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Start with simple well supported terrain below treeline and gather information before stepping out.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

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