Avalanche forecast

Kootenay Boundary

Feb 28 – 29, 2012Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Winds are forecasted to be blow out of the SW at Moderate values Wednesday. With all of the dry snow available for transport, wind slabs could easily form in wind exposed terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–7
    The Feb 08 surface hoar/facet/crust combination is now buried by up to a meter of new snow. This snow has consolidated into a slab. Avalanches triggered on this layer will likely be large, destructive & potentially deadly.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Storm slabs from the weekend continue to be sensitive to the weight of a skier or sledder. Storm slabs are capable of size 2 avalanches & they may step down and trigger the persistent slab avalanche.

Confidence

Good

Weather Forecast

A low pressure system moving across Washington will deliver bands of precipitation to the boundary Wednesday. I Expect 10 - 15 cm of snow out of this system with winds out of the SW at generally moderate speeds. Wed. 1500m Temp: H: -3, L: -7. On Thursday a weak ridge builds back into the region and no significant precip is expected. Thur. 1500m Temp: H: - 3, L: -16. The ridge flattens back out on Friday, opening the door to zonal flow for most of the province. 8 - 15 cm are expected Friday evening.

Avalanche Summary

Lot's of activity to report from Monday: Explosive work produced avalanches to size 3.5, running on the Feb. 08 surface hoar. Two size 3 natural avalanches were reported too. (See the incident submission linked to this forecast, great photos.) The sun is beginning to have an effect on S &W facing slopes, there were some reports of solar induced activity to size 2 Monday. Loose snow avalanches running in the weekend snow continue to be observed.

Snowpack Summary

The weekend storm snow continues to sluff in steep open terrain, but the big story continues to be the buried surface hoar, now down an average of 100 cm below the snow surface. Avalanche activity on this layer has slowed a bit, but it is still producing. When it goes, it goes big as evidenced by Monday's observations (See Avalanche Observations below.) This layer continues to produce size 3 avalanches which by definition are big enough to destroy a car or woodframe house. Professionals throughout the region are treating this layer with extreme caution, since it is showing signs of remote triggering and the ability to propagate in low angled terrain. In the alpine there may be enough wind to create new windslabs that are softer and probably will not bond well to the old surface.

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