Avalanche Forecast

Issued: Apr 5th, 2017 4:26PM

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

mbender, Avalanche Canada

Sea To Sky.

A series of pacific frontal systems impacting the coast in the coming days will elevate the avalanche danger.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Friday

Weather Forecast

THURSDAY: Flurries, accumulation 5-10cm / Moderate south wind / Alpine temperature -2 / Freezing level 1500mFRIDAY: Snow, accumulation 20-25cm / Moderate to strong south wind / Alpine temperature -1 / Freezing level 1500mSATURDAY: Flurries, accumulation 5-10cm / Moderate to strong southwest wind / Alpine temperature -4 / Freezing level 1200m

Avalanche Summary

Reports from Wednesday include explosives triggered storm slabs running to size 2, 30cm deep. On Monday a few natural cornice releases to size 2.5 were observed running to the bottom of their run outs entraining loose snow only. On Sunday, a natural cornice release triggered a size 3 slab avalanche which release down 60 cm and ran to valley bottom. On Thursday, expect newly formed wind and storm slabs to be reactive to human triggering. These slabs are expected to be particularly touchy where they overlie a melt-freeze crust.

Snowpack Summary

20-30cm of new snow at upper elevations sits on widespread melt-freeze crusts on all aspects and elevations except for high elevation north facing terrain. On all aspects below 2000 m and higher on sun exposed slopes, there may be multiple crust layers in the upper snowpack. Moderate to strong alpine wind from the south will have redistributed this new snow and formed additional wind slabs in the alpine and at tree line which may overlie a crust. Large overhanging cornices exist primarily on north aspects in the alpine.

Problems

Storm Slabs

The combination of new snow, moderate to strong southerly winds and warm temperatures have created reactive storm slabs. These are expected to especially touchy in the lee of exposed terrain features.

Use extra caution on steep open slopes and unsupported convex rolls.Use ridges or ribs to avoid pockets of wind loaded snow.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

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 6th, 2017 2:00PM