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Avalanche Forecast

Archived

Mar 1st, 2014–Mar 2nd, 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.

Conditions remain prime for human-triggered avalanches. Check out this great video from the S.R. field team on the tricky persistent weak layer and current avalanche problem. Also see this recent blog post on difficult decision-making.

Confidence

Good

Weather Forecast

Unsettled conditions are expected for the forecast period with light, scattered flurries and periods of sun. Air temperatures should rise on Monday as the arctic air regresses. Sunday: Cloudy with sunny breaks, snow flurries 1-3cm, treeline temperature around -16C, ridgetop winds increasing to 30-50 km/h SW in the afternoonSun. Night/Monday: Cloudy with sunny breaks, flurries 1-3cm, freezing level around 1300m, ridgetop winds 40-60 km/h SWTuesday: A mix of sun and cloud, flurries 0-2cm, freezing level around 1500m, ridgetop winds 30-50 km/h SW

Avalanche Summary

No new avalanches were reported on Friday. On Thursday, we received reports of several loose, moist avalanches up to size 2.

Snowpack Summary

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 new video discussing the persistent weak layer and the current avalanche problem. Variable winds have transported some of the surface snow, building wind slabs on leeward slopes. Strong SW winds are forecast to begin on Sunday and should result in new, touchy wind slab formation.  Large cornices remain a concern along ridge lines and threaten the slopes below. South facing slopes have formed a sun crust on the snow surface. New surface hoar formation up to 4mm and near-surface faceting are also being reported. 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.