Boletín de aludes

Kootenay Boundary

Mar 2 – 3, 2022Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

Fri
Sat
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Lo esencial

Though natural avalanche activity will taper off, conservative decision making is essential to let the snowpack adjust to the recent 65+ mm of load that the Kootenay-Boundary has received. 

Seek out low angle, well supported terrain away from overhead hazard.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Two buried persistent weak layers could be potential problems under the recent load of new snow.

    A weak layer from mid-February is likely down over 60 cm and may become more reactive as the overlying snow forms a thicker and more cohesive slab. Two weak layers of surface hoar from January are likely down around a meter and were primarily a concern in the east of the region on northerly aspects around treeline. 

    Storm slab and loose wet avalanches have the potential to step down to these deeper layers. 

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–3

    Human triggered avalanches will continue to be likely so make conservative terrain choices and give the recent storm snow time to settle and stabilize.

    With no overnight refreeze, elevated freezing levels, and rain-soaked snow at lower elevations, storm slabs may entrain wet loose snow and run further than expected. 

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Since we likely won't get a good overnight refreeze, loose wet avalanches may be a concern at lower elevations where rain has destabilized the snowpack causing it to lose cohesion. These avalanches can start from a point and pick up a surprising amount of mass, especially in steep terrain and gully-type features. Storm slabs may entrain wet loose snow at lower elevations and run further than expected. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Use small low consequence slopes to test the bond of the new snow.
  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Tuesday night: light snow possible 0-5cm, moderate to strong southwest wind, freezing levels likely remain elevated hovering around 1700-1900 m, treeline highs around +2.

Wednesday: Light snowfall trace amounts possible, light to moderate southwest wind, freezing levels around 1700 m, treeline highs +2.

Wednesday night into Thursday: Light flurries possible 0-5 cm, wind light and variable, freezing levels between 1500-1700 m during the day.

Friday: Clearing, good overnight recovery, light to moderate northeast wind, treeline highs around +2.

Avalanche Summary

On Tuesday explosives control triggered large slab avalanches in the size 2-3 range. Although visibility has been poor a couple of natural storm slabs in the size 2.5 range have also been spotted.

On Monday there were various reports of natural and rider-triggered avalanches in the size 1-2 range, some with surprising propagation.

Snowpack Summary

The storm started cool and then it got warm! Some places in the Kootenay boundary have received over 60 mm of water from this system. That has translated to about 20-40 cm of heavy, upside-down type snow forming reactive slabs on all aspects. Rain runnels have been reported up to about 1800 m. The new snow sit on top of sun crusts on south-facing terrain, freezing rain crusts, old wind-pressed snow, and cold weak snow crystals on shaded aspects. Moderate to strong southwest winds have likely contributed to cornice growth and some wind loading as well.

Weak layers from mid-February and late January made up of crusts and/or surface hoar crystals can be found around 60-70 cm deep. There are not a lot of recent avalanches on these layers, but they are still on the radar of operators in the area.

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