Avalanche Forecast

Issued: Mar 31st, 2016 9:06AM

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

rbuhler, Avalanche Canada

South Coast.

A special warning has been issued for the substantial warming and sun this week. Extra caution is required around and below cornices, and on steep sun exposed slopes during the heat of the day. Deep persistent avalanches may also become possible.

Summary

Confidence

Moderate

Weather Forecast

The ridge of high pressure is expected to persist until Friday night when a weak frontal system reaches the coast. Friday should be sunny with light alpine winds and freezing levels around 3000m. Partly cloudy conditions are expected for Saturday with moderate southwest winds in the alpine and freezing levels dropping to around 2000m. Partly cloudy conditions are expected for Sunday with light to moderate southwest winds in the alpine and afternoon freezing levels around 2000m. A weak storm system is currently expected to arrive Sunday night.

Avalanche Summary

On Wednesday, a skier triggered a size 1.5 avalanche on a south aspect at 2200m which was 10-40cm deep with the most recent snow sliding on a crust. Loose wet avalanches up to size 2.5 and cornice releases up to size 2.5 were also reported. On Tuesday, widespread natural loose wet sluffing was reported on solar aspects up to size 2.5. A natural size 2 wind slab avalanche was also reported in large open icefield area caused by down flowing wind. Natural cornice failures up to size 2.5 were also observed. On Friday, continued warming, sun exposure, and limited overnight recovery means natural cornice releases and loose sluffing are expected to continue, and wet slab avalanches are possible. As the warm temperatures continue, deep persistent weak layers have the potential to become reactive and produce very large slab avalanches.

Snowpack Summary

A moist snow surface is reported to be widespread to mountaintops except for shaded true north aspects at the highest elevations. Warm overnight temperatures means there was a limited refreeze of the snow surface. A weak crust was reported to have formed in some areas but is expected to quickly break down in the morning. Wind affected surfaces are reported in exposed alpine terrain in response to recently strong northerly winds. Large cornices are lingering and are expected to become very weak with the sustained warming this week. Below the snow surface, there are two layers of concern in the northern half of the region. Professionals are tracking a melt freeze crust down around 40cm and a thick layer of facets down 120cm. As the snowpack continues to heat up this week, these layers have the potential to wake-up and produce very large avalanches.

Problems

Cornices

Large cornices are expected to get weak with warming and sun exposure, and natural cornice releases are possible in the afternoon. 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. >Extra caution needed around cornices with current conditions. >Give cornices a wide berth when traveling on or below ridges. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Loose wet sluffing is expected on sun exposed slopes during the heat of the afternoon. Very warm conditions may increase the size and run length of natural sluffing.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Start and finish early before the surface crusts melt. >Be cautious of sluffing in steep terrain.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Deep Persistent Slabs

There is concern that buried weak layers may wake-up with the warming this week, especially in the northern half of the region. Pros are tracking a crust down 40cm and a facet layer down 120cm. Very large avalanche may be possible in isolated areas.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 1st, 2016 2:00PM