Avalanche Forecast

Archived

Apr 10th, 2013–Apr 11th, 2013

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Cariboos.

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

Thursday: Light snowfall / Light northwest winds / Freezing level at 1100mFriday: Light snowfall becoming moderate in the afternoon / Strong southwest winds / Freezing level at 1100mSaturday: Light to moderate snowfall / Light southwest winds / Freezing level at 1100m

Avalanche Summary

On Monday a couple of slab avalanche to size 2.5 were remotely triggered by a skier from 300m away. The avalanches occurred on a northwest aspect in the high alpine. The early April surface hoar/ facet interface is though to be the culprit. No new avalanches were observed on Tuesday; however, observations were very limited. I would expect a new round of wind/storm slab activity in the wake of new snow and wind on Wednesday.

Snowpack Summary

At upper elevations moderate to locally heavy amounts of new snow have been shifted into deeper windslabs by steady southwest winds. About 40-75cm below the surface you are likely to find a temperature/sun crust from last week's clear weather. At the same interface you may find a touchy layer of facets or surface hoar on shaded alpine slopes above ~2400m. Where they exist these weak crystals have been responsible for large remote triggers. The variable and reactive nature of this layer suggests that it may continue to catch people by surprise. At lower elevations (below 1600m) rain has continued to saturate the snowpack. Recent snowfall and wind have made large cornices bigger and more likely to fail.

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.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.