Bollettino valanghe

Purcells

Dec 27 – 28, 2020Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 6 years ago

Pericolo valanghe

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

In sintesi

  

Buried weak layers in the middle and bottom of the snowpack continue to be a significant concern. Conservative terrain choices are key to avoiding these large and destructive avalanches.

Problemi valanghivi

  • Wind Slabs

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

    Wind switching directions has created wind slabs on a variety of aspects.

  • Persistent Slabs

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

    A weak layer of surface hoar down 40-90 cm. has been reactive to human triggers, resulting in large avalanches.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2.5–4

    A Crust buried near the bottom of the snowpack has been responsible for some very large explosive triggered avalanches up to size 4.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

 SATURDAY NIGHT: Cloudy with flurries; 0-3 cm. / Moderate to strong, northwest ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.

SUNDAY: Mostly cloudy with sunny periods. / Light, northwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.

MONDAY: Cloudy / Light, northwest ridgetop wind / alpine high temperature -9 / Freezing level valley bottom.

TUESDAY: Mix of sun and cloud / Light, northwest ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.

Avalanche Summary

On Wednesday there was a report of a snowmobile triggered size 2 deep persistent slab avalanche in the north of the region. This MIN post highlights the avalanche and the current nature of the snowpack.

On Tuesday there were several reports of deep persistent slab avalanches running size 2-3 on southeast, east and northeast aspects. Three of these were size 2's triggered by skiers. Check out this MIN report from Tuesday afternoon for an example. 

Snowpack Summary

30 to 75 cm. of storm snow fell last weekend and into Monday. Winds blowing from a variety of directions formed slabs in lee features at upper elevations, reactive cornices have grown too. 

Below the storm snow, there are several critical layers of concern. The early December surface hoar is down 30 to 80 cm. It has recently been sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.

Below, or near the surface hoar you may encounter a crust. This crust has been observed as high as 2400 m. in the south of the region and 1800 m. in the north.  

The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers in steep, shallow, rocky areas with a thin to thick snowpack.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Regioni coperte