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Avalanche Forecast

Archived

Feb 1st, 2012–Feb 2nd, 2012

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 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.

Regions

Cariboos.

Confidence

Good - -1

Weather Forecast

A strong ridge of high pressure is expected to keep the region mostly clear and dry for the forecast period. Moderate northerly winds on Thursday are expected to shift to southerlies of Friday, before diminishing on Saturday. Freezing levels are expected to hover around 1000m on Thursday before spiking to 2000m on Friday, but back down to 1500m for Saturday.

Avalanche Summary

Recent reports include a couple of natural cornice-triggered 70-80cm thick wind slab avalanches as big as Size 3 on north and northeast facing alpine slopes. One natural Size 2.5, 80cm thick slab avalanche associated with the mid-January facets was observed on a southeast facing slope at 1600m. Check out the incident database (link under the Bulletins tab) for a report of a slope-cut stepping down to the mid-January facets in the Monkton Creek area near Barkerville. Large persistent slab avalanches that propagate across entire slopes are possible, especially with heavy triggers such as step-down avalanches and cornice falls. The recent storm snow also remains sensitive to human triggers with several small sluffs and Size 1 to 2, 35-45cm thick slab avalanches.

Snowpack Summary

Total snowpack depths are well above average or even new record depths for this time of year. Recent warm temperatures and upside-down storms created a touchy surface slab. Other weaknesses within and under (mid-January facets) the 100-150cm of settled storm snow create the potential for step-down avalanches, but things seem so be settling rapidly. Moderate southerly or southwesterly winds have created wind slabs and large fragile cornices in exposed lee and cross-loaded terrain. Snowpack tests on the mid-January facets consistently produce sudden fractures. This weakness seems to be particularly touchy below 1500m where there is an associated crust.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.