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Avalanche Forecast

Archived

Jan 30th, 2012–Feb 1st, 2012

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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Cariboos.

Confidence

Good - -1

Weather Forecast

Tuesday: Light snowfall with moderate southwesterly winds and freezing levels near valley bottoms. Wednesday: A clearing trend with freezing levels as high as 1000m. Thursday: A temperature inversion with associated valley cloud is possible.

Avalanche Summary

Reports are coming in about a widespread natural avalanche cycle that occurred Saturday night and Sunday morning with very large avalanches running full-path on all aspects and elevations. Storm slabs continued to be highly sensitive to human triggers on Sunday with slope-cut avalanches up to Size 2 on steep unsupported features and gullies at treeline and below.

Snowpack Summary

Recent warm temperatures and upside-down storms created a touchy surface slab. Other weaknesses exist within and under the 150+cm of recent storm snow, 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. All this new snow increases the load (stress) on deeper layers created during the mid-January cold snap; namely facets (sugar) and a crust at lower elevations (say 1500m and lower). This layer is now deeply buried (around 200 cm or more in many places) but snowpack test results on this layer range from no result to easy (variable strength) but the shear pops (if triggered it wants to propagate).

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.

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.