Bollettino valanghe

Kootenay Boundary

Jan 6 – 7, 2022Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 5 years ago

Pericolo valanghe

Sat
Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Apri la mappa completa

In sintesi

Avalanche danger will rise through the day as the next storm brings new snow and wind. If you see more than 25 cm of new snow, treat avalanche danger as HIGH.

The region continues to deal with a tricky persistent slab problem and very large avalanches remain possible.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    A deeply buried weak layer has produced a number of large and surprising avalanches in the past week and a half. As new snow loads and smaller storm slab avalanches further stress this layer, we may continue to see avalanche activity on it.

    This problem is most likely to be triggered from thin or variable depth snowpack areas such as wind affected features, ridge crests, and near rocky outcroppings.

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    As the next storm rolls in, new snow and wind will bolster the storm slab problem. Even in places that receive minimal new snow Thursday, plenty of recent, low density snow is available for transport into wind slabs as winds pick up ahead of the storm's arrival. New and recent snow may overlie a weak interface which could result in deeper and touchier than expected storm slabs.

Snowpack Summary

As the next storm rolls in, areas west of Castlegar can expect upwards of 20 cm of new snow to fall Thursday. The bulk of snowfall won't arrive in eastern areas until Friday but increasing winds can be expected to transport 40-70 cm of recent snow into reactive wind slabs in lee terrain features. The recent snow sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 5 mm in sheltered areas. Reactivity at this interface may persist for longer than usual.

The early December crust/facet layer has been responsible for numerous very large persistent slab avalanches over the past week and a half. The depth of the crust ranges widely from 80-190 cm and has most recently been reactive in wind affected terrain near ridge crests. Nearly all of the recent avalanches on this layer have been triggered from shallow spots in the snowpack where the crust is less than 100 cm deep. Avoid steep, rocky slopes with a shallow or thin-to-thick transitions in the snowpack.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

Wednesday night: Cloudy. Light SW wind. Treeline temperature around -12 °C. 

Thursday: Snowfall 10-15 cm in most areas, upwards of 20cm west of Castlegar. Moderate SW wind. Treeline high around -9 °C. 

Friday: Snowfall 20-40 cm in most areas, upwards of 50 cm at Kootenay Pass. Strong SW wind. Treeline high around -3 °C. 

Saturday: Mix of sun and cloud. Moderate SW wind. Treeline high around -6 °C. 

Avalanche Summary

On Monday and Tuesday, storm slab avalanches were reactive naturally and to skier and explosive triggers, up to size 2. Recent snow appears to sit on a weak interface which may result in storm slab reactivity persisting longer than normal.

There has been an alarming pattern of large, persistent slab avalanches being consistently reported over the past week and a half. Almost all of these avalanches ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern. Additional loading by the weight of new snow will further stress this weakness and may result in a resurgence of reactivity.

  • On Tuesday, explosive control work near Rossland produced a size 2.5 persistent slab avalanche on a layer of surface hoar from late December. 
  • On Monday in the neighboring South Columbia region, a natural size 2.5 persistent slab avalanche was reported on a NE aspect at 2200 m failing 80 cm deep on the early December layer.
  • A few notables from last week feature in our latest blog Photos of recent persistent slab avalanches in the southern interior. 

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Dial back your terrain choices if you are seeing more than 25cm of new snow.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • It's critical to stay disciplined and choose only well supported, low consequence lines.

Regioni coperte