Avalanche Forecast

Issued: Mar 11th, 2016 7:16AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Cornices.

rbuhler, Avalanche Canada

South Coast.

Ongoing snowfall and strong southerly winds will add more load to already thick storm slabs and large cornices. Conservative terrain selection is critical this weekend.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Storm systems are expected to impact the south coast all weekend but it looks like the bulk of the snowfall will be confined to the immediate coast. 10-20cm of new snowfall is expected by Saturday morning. Freezing levels are expected to drop to around 1000m and alpine winds are forecast to be strong from south. Another 5-15cm of snowfall is expected on Saturday with freezing levels around 1000m and strong alpine winds from the southwest. Light snowfall is forecast to continue on Saturday overnight and Sunday morning with another 10-20cm of snowfall possible. Periods of clearing are expected between storm pulses over the weekend but there is lots of uncertainty regarding the timing. Unsettled conditions are currently expected for Monday with light snowfall and sunny breaks both possible.

Avalanche Summary

Observations were limited on Thursday due to the stormy conditions but a natural size 2.5 storm slab avalanche was reported from the north of the region. The occurred on southeast through southwest aspects at 2100m and the slab was 70-100cm thick. Some natural activity was reported from the Duffy on northern aspects. Natural activity remains possible on Friday in steep freshly wind-loaded terrain. More widespread storm slabs are expected to remain sensitive to human-triggering, especially on steep unsupported terrain features and wind loaded slopes.

Snowpack Summary

30-60cm of new snowfall has accumulated in sheltered areas with greatest amounts to the north of the region. Weaknesses within or at the base of the new storm snow may need a couple days to settle and strengthen. Extreme southerly winds have created very deep and dense slabs in lee terrain, probably well below ridge crests, while scouring windward slopes. This intense loading may have overloaded a weak layer of surface hoar buried at the beginning of February. This layer was primarily a concern in the South Chilcotin Mountains. Where it has not been flushed out or squashed, it would be 100-150 cm deep now. Ongoing stormy weather has also encouraged extensive cornice growth.

Problems

Storm Slabs

Widespread storm slabs are expected to be reactive to human-triggering, especially in wind loaded terrain.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain. >The new snow will requires several days to settle and stabilize. >Avoid freshly wind loaded features. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Cornices

Cornices are reported to be massive and weak. These could pop off at any time, but are more likely to fail with continued growth or during brief sunny breaks.

Give cornices a wide berth when travelling on or below ridges.>Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 12th, 2016 2:00PM