Avalanche forecast

South Columbia

Dec 31, 2017Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

The new year will bring a more stable weather pattern along with gradually warming temperatures. Consider the potential to trigger persistent slabs as the recent storm snow starts to finally settle and consolidate more rapidly.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    A weak layer of surface hoar buried 60-100 cm deep has potential to produce large avalanches where the overlying snow has settled into a cohesive slab.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    35 to 60cm of low density new snow has accumulated in the region the past 3 days. Where accumulations are higher expect the new snow to sluff and gather mass in steep terrain. West and northwest winds have created windslabs in alpine lees.

Weather Forecast

SUNDAY: Mix of sun and cloud / Light to moderate west wind / Alpine temperature -10 MONDAY: Mix of sun and cloud / Light to moderate northwest wind / Alpine temperature -5 TUESDAY: Mix of sun and cloud / Moderate northwest wind / Alpine temperature 2, possible temperature inversion

Confidence

Moderate - Freezing levels are uncertain on Tuesday

Avalanche Summary

Recent reports show numerous natural and human triggered loose dry avalanches in steep terrain to size 1.5 and also a few natural storm slab avalanches to size 2 in the alpine. There have been a few reports of persistent slab avalanches both naturally and remotely triggered to size 1.5 and 2 on north aspects between 2000 and 2200m. Consider the potential to trigger persistent slabs on top of the mid December persistent weak layer as the temperature rises and the storm snow begins to settle and consolidate more rapidly in the coming days.

Snowpack Summary

35-65cm of low density new snow from the past 3 days has buried a recently formed layer of weak feathery surface hoar and/or sugary facets. A layer buried mid-December that consists of surface hoar, sun crust and/or sugary facets is now down approximately 60-100cm.The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, such as sheltered areas at and below treeline, sheltered northerly aspects in the alpine, or anywhere the surface hoar formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this weak layer but suggest that it may be most reactive on northerly aspects. A rain crust that formed in late November is now buried 100-140cm deep. Recent evidence from the North Columbia region suggests it may be reactive in steep, variably loaded terrain features in the alpine.

Regions covered