Avalanche Forecast

Archived

Jan 25th, 2012–Jan 26th, 2012

Alpine

Natural and human triggered avalanches likely.

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 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

South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain on Wednesday

Weather Forecast

Thursday: Light snowfall in the morning with clearing expected by the afternoon. / winds moderate from the west / freezing level at surface Friday: mostly clear / light northwest winds / freezing level at surface Saturday: Mostly clear / light westerly winds / increasing cloud and rising freezing levels in the afternoon

Avalanche Summary

A recent size 2.5 natural was observed on an alpine feature in the Duffey Lake area on Wednesday. No other avalanches have been reported, most likely because of poor visibility.

Snowpack Summary

By thursday morning another 10-15cm of snow should have fallen adding to the 50cm of snow that fell in the past few days. These systems were accompanied by strong southwest winds. Add all of this to the 25-40cms that fell over last weekend that now sits on top of the previous cold, low density snow from the last week and you've got a great recipe for storm and wind slab development. A weak interface exists lower in the snowpack down 40-70cms. This interface consists of old decomposing snow crystals, preserved snow crystals (stellars), and facets (sugary crystals). Tests done on this interface are showing moderate to hard results, but sudden planar characteristics. This may be a layer to watch with more snow and wind forecast. The rain crust itself lies buried around 40-60cm below the surface at 1900m and below. 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. Weak layers lower in the snowpack have generally ceased to be of concern, except perhaps in very isolated, thin rocky areas.

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.