Avalanche Forecast

Issued: Mar 31st, 2016 8:22AM

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

rbuhler, Avalanche Canada

Sea To Sky.

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.

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. Cloudy conditions are expected for Saturday with moderate southwest winds in the alpine and freezing levels dropping to around 2000m. Light scattered flurries are possible on Saturday. A mix of sun and cloud is expected for Sunday with light to moderate southwest winds in the alpine and afternoon freezing levels around 2000m. A more substantial storm system is currently expected to arrive Sunday night.

Avalanche Summary

On Wednesday, a natural size 2 was reported on a south aspect at 2000m. Skiers triggered a size 1.5 avalanche on a south aspect at 2200m. These avalanches were 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 3 were also reported. On Tuesday, a skier triggered a small wind slab in steep rocky terrain on a west aspect at 2300m and went for a ride. A skier also triggered a size 2 storm slab on a north aspect at 1800m which was 20cm thick. Explosives triggered several cornices up to size 2.5 and no subsequent slabs were reported. Widespread natural sluffing was also reported up to size 2.5. 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.

Snowpack Summary

A moist snow surface is reported to be widespread to mountaintops except for shaded true north aspects above 2000m. 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, the mid snowpack is generally well-settled throughout with no notable persistent weaknesses.

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.

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

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. >

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Wet Slabs

Where old storm snow overlies a buried crust, wet slab avalanches may be possible.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Even small avalanches may run a long ways under the current conditions. >Travel early before the heat of the day, and avoid big slopes in the afternoon. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

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