Archived

Avalanche Forecast

Apr 6th, 2017–Apr 7th, 2017

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

Yet another Pacific frontal system will impact the region keeping the avalanche danger elevated

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

FRIDAY: Periods of snow, accumulation 15-25cm / Moderate to strong south wind / Alpine temperature -3 / Freezing level 1600mSATURDAY: Mainly cloudy with isolated flurries, accumulation 5-10cm / Moderate southwest wind / Alpine temperature -6 / Freezing level 1300mSUNDAY: Mainly cloudy / Light south wind / Alpine temperature -8 / Freezing level 900m

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 Friday, 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

25-40cm 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.

Avalanche 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.

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

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.

Give cornices a wide berth when traveling on ridgesEven small cornice falls may trigger larger avalanches on slopes belowAvoid exposure to slopes that have cornices overhead

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 3