Avalanche Forecast

Issued: Apr 5th, 2017 4:21PM

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

mbender, Avalanche Canada

South Coast Inland.

There is distinct variability in avalanche conditions between the north and south of the region. In the north of the region recent heavy loads such as cornice falls have been sporadically triggering full depth avalanches.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Friday

Weather Forecast

THURSDAY: Scattered showers or flurries, accumulation 5cm / Moderate south wind / Alpine temperature -1 / Freezing level 1600mFRIDAY: Flurries in the north and a mix of rain and snow in the south, accumulation 5cm in the north and 25-30cm in the south / Moderate to strong south wind / Alpine temperature -1 / Freezing level 1600mSATURDAY: Flurries, accumulation 5-10cm / Moderate to strong southwest wind / Alpine temperature -3 / Freezing level 1200m

Avalanche Summary

A Mountain Information Network post from Monday describes a cornice triggered avalanche stepping down to the November deep persistent weak layer or ground in the alpine on a North aspect. Click here to read more details in the post itself. An additional report from Monday indicates a size 2.5 explosives controlled cornice failure stepping down to what was suspected to be a mid-February persistent weak layer in the Duffy Lake area. Yet another report from the same area indicates a size 3 large explosives triggered avalanche stepping down to what was suspected to be a November persistent weak layer. There have been no new avalanche reports from the Coquihalla area or south of the region in the past several days.On Wednesday, 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

Anywhere from 5 to 15cm of new snow is sitting on a widespread melt-freeze crust on all aspects and elevations except for high elevation north facing terrain. Recent strong winds from the south have formed new wind slabs in the alpine and have added load to cornices. On sun exposed slopes and at lower elevations, several crusts likely exist in the upper snowpack which are generally well bonded. Both the mid February persistent weak layers and November deep persistent weak layer seem to have become reactive to heavy loads (cornice falls and/or large explosives triggers) at upper elevations in the northern part of the region near the Duffey Lakes and Birkenhead Lake.

Problems

Cornices

Large cornices may become weak with daytime warming or during periods of stormy weather. Recent cornice falls have been triggers for full depth avalanches in the north of the region.

Cornices become weak with daytime heating or solar exposureGive cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Wind Slabs

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

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Deep persistent slabs have been shown to be reactive to heavy loads (i.e. smaller avalanches stepping down or cornice triggers) in the past few days

Pay attention to overhead hazards like cornices which could potentially trigger deeper weak layersAvoid convexities or areas with a thin or variable snowpack.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 6th, 2017 2:00PM