Avalanche Forecast

Issued: Mar 12th, 2016 7:09AM

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

Weather Forecast

Another 5-10cm of snowfall is expected Saturday overnight with freezing levels around 1000m and moderate alpine winds from the south. A bit of a break is expected in the morning with another 5cm of snowfall is expected on Sunday afternoon. Afternoon freezing levels are expected to be around 1300m and alpine winds are forecast to be moderate from the south. Light snowfall is forecast to continue Sunday overnight. Mostly dry and cloudy conditions are expected for Monday with snow flurries and sunny breaks both possible. Freezing levels are expected to be around 1300m in the afternoon and alpine winds are forecast to be light from the southwest. A mix of sun and cloud is forecast for Tuesday with freezing levels around 1400m and light alpine winds.

Avalanche Summary

On Friday, two natural cornice triggered storm slabs were reported in the north of the region. One was a size 3 storm slab on a northeast aspect at 2000m and was 100cm thick. It was reported to have run full path to the end of the runout. The other was a size 2 on a northeast aspect at 2200m that was 30-60cm thick. On Thursday, a natural avalanche cycle occurred in the north of the region with storm slabs up to size 2.5 reported. Storm slabs are expected to remain touchy to human-triggering on Saturday and natural activity is possible in freshly wind loaded terrain.

Snowpack Summary

40-70cm 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. Strong southerly winds have created 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 freshly wind loaded features. >The new snow will requires several days to settle and stabilize. >Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain. >

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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 13th, 2016 3:00PM