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Avalanche Forecast

Archived

Mar 10th, 2013–Mar 11th, 2013

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, 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.

Regions

South Columbia.

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Overnight and Monday: A weak disturbance is moving Southwards across the Interior Ranges bringing light precipitation and strong Northerly winds. Freezing levels should drop to valley bottoms overnight and then rise to about 1500 metres.Tuesday: A Low pressure system is expected to track inland from the South Coast during the day bringing moderate to heavy precipitation and freezing levels rising up to about 2000 metres. Winds becoming strong Westerly.Wednesday: Another frontal system is expected to move inland from the coast.

Avalanche Summary

One skier accidental size 2.0 avalanche was reported from the Selkirks in the South of the region near the Kootenay Boundary region border; see incident report database for more info. Loose moist snow and natural cornice falls resulted in numerous avalanches in the Selkirks and Monashees during the period of strong solar radiation on Saturday. No avalanches were reported to have released on the February 12th weak layer.

Snowpack Summary

New wind slabs are developing above a new surface hoar layer on shaded aspects and a sun crust on solar aspects. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cm and was not triggered by cornice falls over the weekend. Some areas report that the February 12th surface hoar is rounding and getting harder to shear in snow profile tests, but continues to give planar shears when it does fail. Avalanches failing on the February 12th layer have become a low probability/ high consequence situation.

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.

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.