Boletín de aludes

North Rockies

Mar 14 – 15, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

Tue
Wed
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Lo esencial

The Sunday hazard is higher (3-3-3) in the north where 35+ cm of new snow has fell. Sunny & warm weather will destabilize the snowpack throughout the region with potential for very large avalanches during peak warming, cornice fall & large loose wet avalanches may be widespread.

Problemas de aludes

  • Persistent Slabs

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

    The persistent slab problem appears to have been put to rest in deep snowpack areas in the west of the region, but on the eastern slopes (e.g. Kakwa/Tumbler Ridge) there have been very large recent natural avalanches. The rising freezing level this weekend may wake this problem up. The most likely triggers are surface avalanches stepping down, cornice fall, or the weight of a machine or a person hitting a thin-spot.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–2

    This problem can be found in the north of the region in areas around Pine Pass where up to 35 cm of new snow fell as of Saturday morning. This snow may be resting on a sun crust on solar aspects which will allow avalanches failing in the storm snow to run further and faster than you'd normally expect.

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–2

    Potentially large loose wet avalanches are possible Sunday, especially on steep solar aspects. This problem will be amplified in areas to the north that received up to 35 cm of recent snowfall.  

    Cornice failure is likely this weekend as the strong mid-March sun and warming temperatures go to work. As cornices impact underlying slopes there is potential for them to trigger persistent slab avalanches.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

The heat is on until Sunday night, and then we get into a nice pattern of warm days and cooler nights.

SATURDAY NIGHT: Freezing level holding around 2000 m, strong to extreme southwest wind, no significant precipitation expected. 

SUNDAY: Scattered cloud cover, freezing level holding between 1500 & 2000 m, strong southwest wind, a bit of rain/snow possible late in the day. Freezing level returning to valley bottom Sunday night.

MONDAY: A few clouds, freezing level rising to 1600 m, moderate west/southwest wind, no significant precipitation expected.

TUESDAY: A few clouds, freezing level rising to 1800 m, moderate southwest wind, no significant precipitation expected.

Avalanche Summary

Our field team noted some loose wet avalanches to size 2 in their MIN while skiing near McBride on Friday. 

The rising freezing level this weekend may induce a natural avalanche cycle as the snow is destabilized by warming temperatures. Some natural cornice failure was noted on Thursday which is likely a portent of things to come. Our field team found some large and disturbingly wide avalanches in the Hasler Tuesday, lots of compelling images in their MIN report here. It's suspected that these are running on facets that are about 80 cm below the surface.

This adds to the tally of recent large avalanches they started collecting in Pine Pass on Monday. All of this activity leaves me feeling uneasy about a big warm up this weekend. 

Snowpack Summary

The northern portion of the region around the Pine Pass has picked up 35 new cm as of Saturday afternoon but very little new precipitation has fallen in the southern 2/3 of the region. This snow is expected to be redistributed by the strong southwest wind and will also feel the heat of the rising freezing levels this weekend.

The freezing level crept up to about 1850 m Friday leaving a sun crust on solar aspects. The freezing level is expected to be higher Saturday night and Sunday with plenty of sun poking through scattered cloud cover. This rise in temperature is going to be a good test for our snowpack. Wind effect is widespread in the alpine and treeline across the region.

About a metre of snow covers a weak layer of facets buried mid-February. Slightly deeper there is a widespread persistent weak layer from late January/early February that consists of surface hoar. It is most prevalent around treeline elevations, but likely reaches into the alpine and in openings below treeline too. These layers are both significantly shallower in the east of the region.

Terrain and Travel

  • Avoid avalanche terrain during periods of strong sun.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

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