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Avalanche Forecast

Archived

Jan 22nd, 2012–Jan 23rd, 2012

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Monday: Up to 10cms of new snow. Ridgetop winds 30-50km/hr from the SW. Freezing levels near 700m. Alpine temperatures near -7. Tuesday: A major system is hitting the coast bringing moderate-heavy precipitation (15-25 mm) and rising freezing levels near 1500m to the inland regions. Ridgetop winds 75km/hr from the SW. Treeline temperatures near -5. Wednesday: Light-moderate precipitation will continue, and freezing levels will start to fall back to 500m early Wednesday into Thursday.

Avalanche Summary

Natural avalanche activity up to size 1.5 occurred on steep, rocky South facing aspects. An avalanche cycle up to size 2.5 was reported on Saturday. Both slab and loose snow activity was noted at all elevations.

Snowpack Summary

Dense new snow is setting up a fresh storm slab on top of the previous cold, low density snow from the last few days. An interface down 30-50 cm just above a rain crust is producing easy but resistant shears in snowpack tests. The rain crust itself lies buried around 40-60cm below the surface up to around 1900m. The bond at this crust is reported to be quite good. On steep slopes, this interface, or the one above it, definitely has the potential to act as a good sliding surface; especially with forecast wind, snow and rising freezing levels. Field tests done in the Duffy Lake area at 2000m on a North aspect show easy collapse shears down 18cms on precipitation particles (stellar, dendrite crystals), and hard resistent planar shears down 36cms on facet/decomposing fragment crystals. Weak layers lower in the snowpack have generally ceased to be of concern, except perhaps in very isolated, thin rocky areas.

Problems

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.

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.