Bollettino valanghe

North Rockies

Dec 11 – 12, 2021Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 5 years ago

Pericolo valanghe

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

In sintesi

The best riding will be found in sheltered areas treeline and below. Avoid overhead hazard and watch for signs of instability such as whoomphing, shooting cracks, and hollow sounds.

Problemi valanghivi

  • Storm Slabs

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

    10-30 cm of new snow overnight will continue into the day. In wind exposed areas, this new snow will be redistributed by southwest winds into deep deposits of wind slab. In more sheltered areas, this storm snow will form a storm slab or loose dry problem, and be particularity reactive where it overlies a crust.  

    There is still some concern for buried weak layers. Where slabs overlie a weak layer they will be more reactive to human triggered and have the potential to create larger avalanches. 

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely - Possible
    Dimensione
    1.5–4

    An early season crust at the base of the snowpack has shown reactivity in the southeast corner of the forecast region. While this layer likely needs a heavy trigger like a cornice collapse, human triggering may be possible on thin rocky slopes in this part of the region. Be cautious as new snow and wind adds load to the snowpack and tests this deeper layer.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Snowfall beginning on Friday evening will continue into the day on Saturday. Later in the weekend is looking quieter with the potential for some clearing.

Friday Overnight: As a strong pacific system passes over the northwest ranges we will see winds increasing overnight along with rising freezing levels, and moderate snowfall. Southwest winds will be strong to extreme at ridgetop, easing to strong into the morning. Freezing levels rise to around 1200m, with 10-30 cm of new snow. 

Saturday: A cloudy day with continued snowfall. Strong southwest winds at ridgetop with accompany 5-20 cm of new snow throughout the day. Freezing levels hovering at 500m with alpine temperatures around -10 C.

Sunday: Partially cloudy with flurries, accumulation up to 10 cm. Moderate to strong southwest winds at ridgetop with alpine temperatures around -15 C. 

Monday: A quieter day with a mix of sun and cloud, light flurries and light to moderate ridgetop winds from the southeast. Alpine temperatures around -15 C.

Avalanche Summary

There have been very limited reports in the past week! If you do head out in the backcountry, please share your observations/pictures/conditions to the Mountain Information Network! Thank you :)

Snowpack Summary

Another 10-30 cm overnight brings this week's new snow totals to 40-60 cm. This new snow came in with strong winds from the southwest, which will be redistributing the new snow into wind slabs in the alpine and exposed areas at treeline. In sheltered areas, the new snow will behave as a storm slab or loose dry problem, particularly where it overlies a crust.

There is still some concern for buried weak layers. Surface hoar has been observed in sheltered areas at treeline and below, now buried under this week's storm snow. The November 27th rain crust is buried 40-100cm and exists up to 1500m in some areas. 

The lower snowpack consists of a series of early season crusts. Cold temperatures will have promoted faceting around these crusts. Shallow alpine slopes along the eastern side of the Rockies towards Jasper may have weaker, faceted snow near the ground. 

Snowpack depths at treeline range from 60cm-200cm, with the shallower value mainly in the eastern side of the range. The alpine snowpack ranges from 150cm-200cm. 

Terrain and Travel

  • Choose conservative terrain and watch for clues of instability.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Regioni coperte