Avalanche forecast

Kootenay Boundary

Mar 11 – 12, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    Generally lurking below ridge crests, behind terrain breaks, and in gullies. Wind slabs will increase in size and sensitivity Monday afternoon as strong winds & new snow come together to form fresh wind slabs in wind exposed terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    3–8
    The deeply buried surface hoar may be forced into action by heavy loading from wind and snow Mon & Tue. The tricky nature of this layer means that terrain at all elevations has the potential to produce large destructive avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    30 - 60 cm of snowfall is expected to begin falling Mon eve, continuing through Tues. eve. If the forecasted amounts come through, storm slabs will likely overload buried weaknesses & may step down producing large avalanches.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

A trough of low pressure anchored over SW BC allows for moist SW flow for the forecast period. Snowfall picks up again around 10 pm Sunday night; the KB is expected to pick up 5 cm overnight. MONDAY: Monday morning should be cool & crisp with freezing levels at valley bottom, but the cold won't last long, freezing levels climb to 1500 m before lunch as snow fall begins. 5 - 10 cm's are expected during the day with strong SW winds at ridge top & a more moderate southerly at treeline. Remnants of a deep pacific low slide through the region Monday afternoon/evening bringing ridge top winds up to extreme. 10 - 20 cm of snow are expected Monday evening. TUESDAY: SW winds in excess of 100 km/h at ridge top persist through most of Tuesday. Another 10 - 20 cm are expected Tuesday with intensities tapering Tuesday afternoon. SW winds in excess of 100 km/h at ridge top persist through most of Tuesday. WEDNESDAY: A brief ridge of high pressure is in place Wednesday morning, but, the current models show another significant system moving into the region Wednesday afternoon.

Avalanche Summary

Low level cloud made for poor visibility Saturday, as a result, there isn't much to report in the way of avalanche activity. Sluggish sluffing in the storm snow was observed in steep terrain on Saturday though.From earlier in the week:Several natural avalanches were reported Thursday to size 3. One noteworthy event was a size 2 avalanche that was triggered by cornice fall. The size 2 ran 50m before triggering a size 3 avalanche in lower angle terrain. The crown was reported to be 200cm in depth, failing on the Feb. 08 SH. One reported avalanche was remote triggered from 20m away on a 35 degree slope.

Snowpack Summary

Kootenay pass picked up 12 cm of rather wet snow Saturday night, but the rest of the region is reporting only a few cm's. This snow adds to a few cm that fell Friday night, all of which rests on 2 - 6mm surface hoar on north aspects and a 2cm sun crust on solar aspects. Moist snow was found Friday to 1800m, I suspect there was little change Saturday. The leap year SH is now down around 40 - 50 cm and is failing as a resistant planar shear in snowpack tests. The early February surface hoar is down 80 - 140cm, snowpack tests show moderate to hard forces generating sudden planar shears on this layer.

Regions covered