Avalanche Forecast

Issued: Apr 8th, 2018 3:58PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Persistent Slabs and Cornices.

mconlan, Avalanche Canada

Sea To Sky.

Freezing levels will rise over Monday along with sunny patches in the afternoon. The warming will weaken the snow and increase the likelihood of triggering slabs, cornices, and loose wet avalanches. Expect the hazard to rise over the day.

Summary

Confidence

Moderate -

Weather Forecast

MONDAY: Cloudy with light morning snow and afternoon clearing, accumulation 2 to 5 cm, light southwesterly winds, alpine temperature -4 C, freezing level 1500 m rising to 2000 m by late afternoon.TUESDAY: A mix of sun and cloud early morning then mostly cloudy with rain switching to snow at higher elevations, accumulation 10 mm, moderate to strong southerly winds, alpine temperature 0 C, freezing level 2600 m dropping to 1700 m over the day.WEDNESDAY: Mostly cloudy with light snowfall, light southeasterly winds, alpine temperature -4 C, freezing level 1500 m.

Avalanche Summary

On Saturday, ski cuts and explosives triggered many cornices and storm slabs. Cornices were generally small (size 1.5), but they triggered slabs on slopes below. The storm slabs were also generally small (size 1 to 1.5), 10 to 20 cm thick. Loose wet avalanches were observed below about 1900 m.

Snowpack Summary

Around 30 cm of recent snow and strong southerly winds have created new slabs at higher elevations. This snow overlies a melt-freeze crust. On ridges, cornices are reported to be large and fragile. At lower elevations, recent precipitation fell as rain, so expect moist or wet snow conditions.A weak layer consisting of surface hoar, facets, or a sun crust from late March is now buried about 60 to 90 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on shady aspects between 1900 m and 2250 m.Below this, the snowpack is well-settled and strong.

Problems

Storm Slabs

Storm slabs formed over the weekend and were reactive to human activity. Expect slab and loose wet avalanche activity to increase as the air temperature warms and if the sun comes out.

Avoid sun-exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Use ridges or ribs to avoid pockets of wind-loaded snow.Observe for the bond of new snow with the old surface before committing into avalanche terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

A weak layer buried 60 to 90 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep terrain or areas with a thin or variable snowpack.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Cornices

Cornices are very large and fragile. The warming trend will quickly deteriorate their stability. Give them a large berth while on ridges and avoid travelling underneath them, as they can trigger large avalanches on slopes below.

Give cornices a wide berth when travelling on ridges.Avoid travelling on slopes below cornices.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Apr 9th, 2018 2:00PM