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Avalanche Forecast

Archived

Mar 3rd, 2014–Mar 4th, 2014

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

Regions

South Rockies.

Confidence

Fair - Due to the number of field observations

Weather Forecast

A series of weak disturbances will result in light intermittent snowfall during the forecast period. Tuesday: Partially cloudy, scattered flurries 1-3cm, freezing level rising to around 1400m, ridgetop winds 30-50 km/h SWTues. Night/Wednesday: Snowfall 2-8cm, freezing level around 1800m, ridgetop winds 30-50 km/h SW-WThursday: Snowfall 4-10cm, freezing level around 1200m, ridgetop winds 20-40 km/h SW

Avalanche Summary

Reports of loose sluffing from steep, rocky terrain. On Sunday, a size 1.5 skier triggered avalanche was reported. This released down 40cm and it is expected to have failed on the early-Feb persistent weak layer.

Snowpack Summary

10-20cm of new snowfall overlies surface hoar, facets, and/or a sun crust on south aspects.  Recent moderate to strong SW winds have created wind slabs in leeward and cross-loaded features. Previous wind from the NE created wind slabs which are now buried by new snow but still may be reactive.The primary concern remains a persistent slab that sits on a stubborn persistent weak layer consisting of a crust, facets, and/or surface hoar. The layer continues to show a high degree of sensitivity to human triggers. Wide propagations and remote triggering remain a concern. In the thinner snowpack areas such as the Crowsnest and northern Elk Valley, the slab is typically 30-60cm thick. In thicker areas such as the Flathead and around Fernie, the slab typically varies in thickness from 70-150cm. Check out the South Rockies Blog for a video discussing the persistent weak layer and the current avalanche problem. A weakness at the base of the snowpack may still exist in isolated areas of the region but triggering has become unlikely.

Problems

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.

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.