Avalanche Forecast

Issued: Apr 8th, 2016 9:22AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Loose Wet, Cornices and Deep Persistent Slabs.

rbuhler, Avalanche Canada

South Coast.

Spring conditions typically means the hazard is highest during the heat of the afternoon. Cornices and loose wet sluffing are spring problems which can be expected on Saturday. Deep persistent avalanches may become possible with sustained warming.

Summary

Weather Forecast

The warm ridge of high pressure persists through the weekend. Saturday and Sunday are expected to be sunny with light alpine winds and afternoon freezing levels around 3000m. Unsettled conditions are expected for Monday with a mix of sun and cloud. Moderate southwest winds are expected in the alpine and freezing levels are expected to drop to around 2200m.

Avalanche Summary

On Thursday, explosives triggered two size 3 persistent slab avalanches north of Pemberton on southern aspect slopes at around 2100m elevation. The slabs were 40-50cm thick and were suspected to have failed on a crust from the end of February. Explosives also triggered two size 2.5 wet slab avalanches. Loose wet sluffing up to size 2.5 was also reported. On Wednesday, natural loose wet avalanches up to size 1.5 were reported. Skiers and explosives were triggering wind slabs up to size 1.5 in leeward features and on steep rolls. A couple point releases triggered slabs up to size 2.5. With warm and sunny conditions continuing, spring avalanche problems are expected to be the primary concerns. Loose wet avalanches and large cornice falls are expected throughout the forecast period. Wet slabs and deeper persistent slab avalanches may be possible while the temperatures remain high and overnight recovery is poor. Lingering wind slabs may also still be a problem on high elevation north aspects.

Snowpack Summary

Little to no overnight recovery was reported on Friday morning leaving a moist or wet snow surface on all aspects and elevations. The early-April crust layer is typically down 10-20cm and is reported to be breaking down due to the warm conditions. Prior to the warming, the recent storm snow had been shifted by strong southerly winds into wind slabs in wind-exposed terrain. These wind slabs may still be lingering in high north facing terrain. There is an old crust layer down about half a meter in the Duffey area and north of Pemberton. This layer has generally be dormant but resulted in a couple avalanches during the last major warming event and produced a couple explosive triggered avalanches on Thursday. With continued warming, this layer could wake-up and become a more widespread problem. Cornices are huge and will become weak with warming and solar radiation.

Problems

Loose Wet

Loose wet sluffing is likely on sun exposed slopes during the heat of the afternoon. Very warm conditions may increase the size and run length of natural sluffing, and wet slabs could also be possible.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Be cautious of wet sluffing in steep terrain. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Large cornices may become weak with afternoon warming and sun exposure. They can be destructive by themselves, and may also become the trigger for a slab avalanche on the slope below.

Cornices become weak with daytime heating, so travel early on exposed slopes. >Give cornices a wide berth when traveling on or below ridges. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

There is concern that a buried weak layer may wake-up with the warming this weekend in the northern half of the region. Very large avalanche may be possible in isolated areas.

Cornice releases have the potential to trigger deeply buried weak layers. >Be aware of the potential for large, deep avalanches due to the presence of buried weak layers. >Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 9th, 2016 2:00PM