Bollettino valanghe

Kootenay Boundary

Apr 11 – 12, 2021Avalanche Canada
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Archiviato · scaduto 5 years ago

Pericolo valanghe

Tue
Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Apri la mappa completa

In sintesi

Watch for an uptick in east winds and be ready to step back if new slabs begin to form before the end of the day. Anticipate the effects of solar warming if the sun pokes out in your area.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Small recent wind slabs in the immediate lee of ridgetop may still react to human triggers on Monday. Up to 30 cm of dry storm snow has now accumulated on a crust in similar terrain (shaded high elevations), so the possibility exists for some slabs to fracture a bit deeper than expected.

    A forecast increase in east winds could start to form new slabs before the end of the day.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–1.5

    Surface snow will tend to lose cohesion and become unstable with solar warming during the day. Avoid exposing yourself to terrain where a small wet loose release could have big consequences.

Confidence

Moderate -

Weather Forecast

Sunday: Clear. Light northeast winds.

Monday: A mix of sun and cloud. Light to moderate east winds increasing over the day and overnight. Alpine high temperatures around -4 with freezing levels to 1600 metres. 

Tuesday: A mix of sun and cloud. Light northeast winds, increasing a bit overnight. Alpine high temperatures around -2 with freezing levels to 1800 metres. 

Wednesday: A mix of sun and cloud. Light to moderate northeast winds. Alpine high temperatures around +1 with freezing levels to 2200 metres.

Avalanche Summary

A MIN report from Saturday gives a great description of the surface instability that formed as new snow was redistributed into a reactive slab below ridgecrest in the backcountry adjacent to Big White. Similar conditions were very likely in place throughout the region. Small natural dry loose releases were also noted on southeast aspects in the Kootenay Pass area.

Looking forward, recent wind slabs may remain reactive, if a bit more stubborn, to triggering in immediately leeward terrain features, with some potential to step down to a 30 cm-deep crust layer. A forecast rise in east winds may also begin to form new slabs before the end of the day. Wet loose instabilities will again come into play in areas that see solar warming, particularly if a crust hasn't already formed.

Tuesday ushers in the start of a substantial warming trend that will begin to expand the extent of wet loose concerns to higher elevation, more shaded aspects and may eventually test deeper snowpack layers.

Snowpack Summary

A new melt freeze crust has formed on the surface on solar aspects to about 2000 metres and on all aspects up to an estimated 1500 metres. Below it, 5-15 cm of new snow through Friday night accumulated over yet another melt-freeze crust on solar aspects and otherwise added to a settled 5-20 cm of snow from last Wednesday's storm. The mid and lower snowpack are well settled and strong.

Solar warming will break down surface crusts and encourage wet loose releases -both natural and human triggered- each day on solar aspects and increasingly toward shaded alpine terrain as freezing levels march upward over the coming days.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Carefully evaluate steep lines for wind slabs.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Regioni coperte