Avalanche Forecast

Issued: Mar 1st, 2014 8:15AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Persistent Slabs and Wind Slabs.

rbuhler, Avalanche Canada

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.

Summary

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

Expect the buried persistent weak layer to continue to produce large and destructive avalanches. Many slopes are still primed for human triggering and remain a concern on all aspects and elevations.

Use conservative route selection, resist venturing out into complex terrain even if you observe no obvious signs of unstable snow.>Remote triggering is a concern, watch out for adjacent slopes.>Avoid unsupported slopes.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Wind Slabs

Older wind slabs still exist in many lee terrain features but are becoming harder to trigger. New wind slabs are expected to form as wind increases on Sunday. Weak cornices also remain a concern in isolated areas.

Be cautious as you transition into wind affected terrain.>Stay well back from cornices.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Mar 2nd, 2014 2:00PM