Avalanche Forecast

Issued: Apr 1st, 2016 9:47AM

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

rbuhler, Avalanche Canada

South Coast.

Hazard is expected to slowly drop with the cooling over the weekend but avalanche problems are expected to linger for a while longer. Extra caution is required around and below cornices, and on steep sun exposed slopes during the heat of the day.

Summary

Confidence

Moderate

Weather Forecast

A mix of sun and cloud is expected for Saturday with freezing levels dropping to around 2000m and moderate southwesterly winds in the alpine. Mostly cloudy conditions are forecast for Sunday with light southwest winds in the alpine and afternoon freezing levels around 2000m. A storm system is forecast to reach the south coast on Sunday evening. 5-15mm of precipitation is currently expected by Monday evening. Freezing levels are forecast to start around 2000m at the beginning of the storm and drop to around 1500m by the end of the storm on Monday.

Avalanche Summary

On Thursday, a natural cornice release triggered a size 2.5 deep slab release in the Duffey area. A few size 2 wet slabs were also reported in the Duffey area. Lots of loose wet sluffing up to size 2 was observed. A size 2 deep persistent slab was also reported from a southwest aspect at 1900m elevation. 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. Cooling temperatures on Saturday will mean that natural sluffing and cornice releases will become less likely, but with all the heat in the snowpack, it will still be possible for human-triggering of cornices and sluffing. It may still be possible for a cornice release to trigger a deep weakness in the north of the region. Once the snow surface develops a widespread supportive crust layer, it will become unlikely to trigger any deep weaknesses.

Snowpack Summary

A moist/wet snow surface is reported to be widespread to mountaintops except for shaded true north aspects above 2600m. The last few nights have seen some limited overnight crust formation which has quickly broken down the following morning. With freezing levels dropping on Saturday, a surface crust is expected to form at higher elevations and not completely break down during the day. Large cornices are lingering and are expected to remain weak until there is a substantial period of cooling. Below the snow surface, there is a layer of concern in the northern half of the region. Professionals are tracking a thick layer of facets down over 1m which likely resulted in a couple deep persistent avalanches which were reported on Thursday. Deep persistent weaknesses will remain a concern until there is a substantial period of cooling.

Problems

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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Loose Wet

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

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

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

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 facet layer down over 1m. Very large avalanche may be possible in isolated areas.

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. >Cornice releases have the potential to trigger deeply buried weak layers. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 2nd, 2016 2:00PM