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Avalanche Forecast

Archived

Apr 20th, 2013–Apr 21st, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

Conditions vary greatly with elevation.  Expect many different surface conditions and keep an eye out for springtime hazards like cornice fall and glide cracks.

Weather Forecast

Light snow will continue today and tonight.  Freezing levels are forecast to be around 1400 m with  moderate NW winds.  The skies will clear for Sunday and Monday as an upper ridge builds.

Snowpack Summary

Up to 20 cm of new, heavy snow has fallen in the last couple days at treeline and above. This covers a variety of surfaces including sun crust, small surface hoar and moist isothermal snow.  The April 3rd crust is down around 50-60 cm. Below treeline snow is isothermal, on some terrain snow still has some hardness and strength to it.

Avalanche Summary

On Monday, there was a skier accidental, size 3.0 on the east face of Mt Swanzy, depth 100cm, 150m wide, suspect April 3 crust. Skiers were not involved, and later the same day a skier accidental, size 2.0, Forever Young couloir, ran to 2/3 fan. Skier got taken down to the fan before self arresting. Both were in the extreme alpine terrain.

Confidence

Due to the number of field observations

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.