Bollettino valanghe

North Rockies

Feb 20 – 21, 2022Avalanche Canada
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Archiviato · scaduto 5 years ago

Pericolo valanghe

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

In sintesi

The south of the region was the hot spot for Saturday's storm. Continue to be conservative with terrain choices as storm slabs are expected to remain reactive to human-triggering.

In the north of the region, the problem is likely more confined to a wind slab problem in lee areas.

Problemi valanghivi

  • Persistent Slabs

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

    A weak layer formed by clear skies in late January exists in the upper meter of the snowpack. In most areas, a firm crust under the most recent storm snow will bridge the weak interface, making human triggering unlikely. 

    On the eastern side of the ranges in shallower snowpack areas, weak snow (basal facets) may exist near the base of the snowpack. 

    Large triggers, like warming, additional load from new snow, and cornice failures could be enough to wake these layers up, initiating large and surprising avalanches. 

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–2.5

    Throughout the day today, northeasterly outflow winds may cause reverse loading, transporting available snow into fresh wind slabs in normally wind-scoured slopes. 

    With greater snowfall amount in the south, we can expect a more widespread storm slab problem to persist. 40-100cm of recent storm snow may bond poorly to the underlying hard melt-freeze crust. Expect deeper and stiffer slabs to exist in wind-loaded features.

    In the north of the region, the problem is likely more confined to a wind slab problem. 10-30 cm of recent storm snow has been redistributed by southwest winds into wind slabs in lee areas. 

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Bundle up in your warmest gear, arctic air is here! 

Saturday Overnight: Continued snowfall, trace to 10 cm of accumulation. Freezing level dropping to valley bottom with alpine temperatures around -15 C. Light to moderate northerly winds.

Sunday: Partially cloudy, light flurries. Alpine temperatures plummeting into the -20s. Light to moderate northeasterly winds.

Monday: Mainly clear. Alpine temperatures around -25 C. Moderate northeasterly winds at all elevations.

Tuesday: Mainly clear. Alpine temperatures around -20 C. Light northeasterly winds. 

Avalanche Summary

Human-triggered storm slab avalanches remain likely on Sunday.

During the peak of the storm on Saturday, several large natural storm slab avalanches were reported from treeline elevations in the Kakwa.

On Thursday, operators in the Dezaiko range reported a skier-triggered storm slab avalanche on a northeast aspect in the alpine. This avalanche was remote-triggered, meaning the person was a distance away from where the slab initiated. 

Snowpack Summary

This week's snowfall has brought 20-100 cm overlying a widespread crust created from a rain event in early February. This 1-20 cm thick crust exists on all aspects and elevations, excluding areas in the high alpine in the south of the region that may remain crust-free. 

Below the crust, 10-40cm of more settled snow exists above the late January weak layer. This layer consists of weak faceted snow, a melt-freeze crust, and surface hoar crystals in isolated sheltered areas at treeline and below. This layer has been increasingly hard to identify in the snowpack and has shown no reactivity in the past week. In many areas, this layer is bridged by the thick crust above it. 

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Closely monitor how the new snow is bonding to the crust.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.

Regioni coperte