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Avalanche Forecast

Archived

Dec 21st, 2016–Dec 22nd, 2016

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

Mostly a storm and wind slab problem, but as the upper snowpack settles, things might start to change. If you see signs of instability, like whumpfs (rapid settlements), or see small rolls peel off, avoid unsupported (convex) terrain features.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Thursday: 5-10 cm new snow is expected. Ridgetop winds southwesterly 60-70 km/h in the morning, diminishing to westerly 40 km/h by the afternoon. Treeline temperatures around -3C. Friday: Light snow in isolated areas, no significant accumulation expected. Winds becoming light northwesterly. Treeline temperatures around -7C. Saturday: Dry and sunny. Light northeasterly winds. Treeline temperatures around -13C.

Avalanche Summary

No new avalanche activity was reported on Tuesday. I suspect a natural avalanche cycle occurred, however; the stormy conditions may have prevented people from getting out, or even being able to see alpine areas and/ or start zones. Forecast ridgetop winds are 60-90 km/hr and steady though Wednesday which will likely initiate another natural avalanche cycle.

Snowpack Summary

50-70 cm of new storm snow sits above a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new storm snow was expected to bond poorly to these old surfaces; however, less avalanche activity than expected has been noted on this layer, indicating the bond may not be quite as poor as expected. The upper snowpack is still soft - as this becomes stiffer and denser, we may start to see more slab avalanche activity on this layer. The mid-November crust is now buried down 70-150 cm and produces variable results in snowpack tests.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.