Bollettino valanghe

North Columbia

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

Pericolo valanghe

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

In sintesi

New snow and wind are forming touchy slabs. A weak layer in the upper snowpack means slab avalanches can be larger than expected. Having the skills to recognize and avoid avalanche terrain will be critical to managing your risk on Saturday. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Up to 1 m of snow from the previous week now sits over a weak layer on a thick crust. This weak layer is most pronounced at mid-elevations at this time. Natural and human triggered slab avalanches were observed on this layer in the days prior to the current storm, so with the additional snow load this weekend we are expecting this layer to be reactive and produce large avalanches.

  • Storm Slabs

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

    New snow and wind are forming fresh, reactive slabs. 

Confidence

High - A small change in the upper snowpack could dramatically change avalanche conditions.

Weather Forecast

Friday night: 5-15 cm of new snow. Strong to extreme southwest wind. Freezing level climbing to 700 m.

Saturday: 10-15 cm of new snow. Strong southwest wind. Treeline temperatures around -5 C. Freezing level 1200 m.

Sunday: 5-10 cm overnight then clearing. Light southwest wind. Treeline temperatures around -8 C. Freezing level valley bottom.

Monday: Flurries with sunny periods. Light southeast wind. Treeline temperatures around -8 C. Freezing level valley bottom.

Avalanche Summary

Reports from Wednesday and Thursday indicate increasing slab reactivity prior to burial by the current storm. There were several reports of natural size 2 avalanches in alpine terrain as well as several human triggered size 1 wind slabs around treeline. The most reactive slabs were on convex wind-affected slopes. Most avalanches were in the top 20-30 cm of snow.

Avalanche activity is expected to be large and widespread on Saturday.

Snowpack Summary

15-30 cm of new snow falls amid strong wind over 30-60 cm of settling snow from the past week. Beneath this recent snow lies a variety of suspect layers. The most prominent and widespread is a crust that formed during last week's atmospheric river. This crust extends into the alpine (as high as 2200 m), and there is potential for a poor bond to snow sitting above it. We are uncertain about how reactive the recent snow will be as it settles over the upcoming days. The snowpack structure is relatively simple beneath the crust, with treeline snow depths around 150-250 cm.

Terrain and Travel

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Travel in alpine terrain is not recommended.
  • The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.

Regioni coperte