Avalanche Forecast

Issued: Apr 3rd, 2017 3:31PM

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

rbuhler, Avalanche Canada

Sea To Sky.

Recently formed wind slabs are expected to remain reactive to triggering on Tuesday. Use extra caution on high elevation north aspects.

Summary

Confidence

Moderate -

Weather Forecast

Mostly cloudy conditions are expected on Tuesday with snowfall beginning in the afternoon or evening. Alpine wind is expected to be light on Tuesday morning and progressively become strong from the southwest by Tuesday evening. Freezing levels are expected to reach around 1500 m on Tuesday afternoon. 10-20 cm of snow is forecast for Tuesday night and another 20-30 cm is forecast for Wednesday. Alpine wind is expected to be strong from the south or southwest and freezing levels are forecast to reach around 1600 m on Wednesday. The storm is forecast to taper off Wednesday night and a mix of sun and cloud is currently expected on Thursday.

Avalanche Summary

On Sunday, a natural cornice release triggered a size 3 slab avalanche which release down 60 cm and ran to valley bottom. Another natural size 2 cornice release did not trigger a slab. Skiers were triggering size 1 soft slabs in wind loaded features. On Saturday, a few natural storm slabs up to size 2 were reported. Numerous natural loose wet avalanches up to size 1.5 were observed on southeast through west aspects. On Tuesday, recently formed wind slabs are expected to remain reactive to human triggering. These slabs are expected to be particularly touchy where they overlie a melt-freeze crust.

Snowpack Summary

Widespread melt-freeze conditions are expected on all aspects and elevations except for high elevation north facing terrain. On all aspects below around 2000 m and higher on sun exposed slopes, there may be multiple crust layers in the upper snowpack including the late-March rain crust which is now typically down 60-80 cm. In high north facing terrain, 20-40 cm of storm snow accumulated over the weekend. Recent strong alpine wind from the south has redistributed this new snow and formed wind slabs in the alpine and at treeline which may overlie a crust. Large cornices exist primarily on north aspects in the alpine.

Problems

Wind Slabs

Wind slabs have recently formed in north facing terrain at higher elevations and are expected to remain reactive to human triggering on Tuesday.

Use extra caution on steep open slopes and unsupported convex rolls.Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

Large cornices may become weak with daytime warming or during periods of stormy weather.

Avoid exposure to slopes that have cornices overheadEven small cornice falls may trigger larger avalanches on slopes belowGive cornices a wide berth when traveling on ridges

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 4th, 2017 2:00PM