Avalanche Forecast

Issued: Jan 1st, 2015 7:41AM

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

Peter, Avalanche Canada

South Coast.

Recent warm temperatures have helped settle the wind slab problem but there is still potential for triggering deep slides in wind loaded terrain.

Summary

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Synopsis: The ridge of high pressure finally flattens allowing a weak disturbance to slide down from the northwest bringing more cloud, moderate westerly winds, and a chance of flurries on Friday. Another pulse is expected on Saturday afternoon maybe 3-5 cm. The snow level stays near valley bottom on Friday and Saturday. Sunday is still a little fuzzy but it looks like we will see moderate precipitation. The freezing level should start to climb to 800 m by the end of the day and winds are generally light.

Avalanche Summary

Recent activity has been primarily loose wet sluffs in steep sun-exposed terrain. On Wednesday there was one report of a size 1.5 wind slab avalanche on an east aspect in the alpine. This slide was triggered by a cornice fall. Earlier in the week there were numerous reports of natural and rider triggered wind slabs up to size 2.5 from southerly aspects as a result of outflow winds.

Snowpack Summary

In open alpine terrain you will find heavily wind affected surfaces with hard and soft wind slabs on south and west aspects and scoured surfaces or dense wind-pressed snow on windward slopes. Steep south facing slopes may also be going through a melt-freeze cycle. In sheltered areas at and below treeline you might find dry faceting powder with surface hoar (SH) growing above. A layer of SH buried last weekend is now down 10-20 cm and was reported to be widespread - one to watch when the snow returns. The mid-December SH layer may still be lurking in specific areas (sheltered, shady, near open water sources) down 40-70 cm. Below 2000 m and buried 60-100 cm deep you might find a crust with facets or mixed forms above or below. One recent snowpack test gave a hard pops result on this layer, meaning its probably difficult to trigger but if triggered it could produce large deep slabs.

Problems

Wind Slabs

Previous outflow winds create dense or hard wind slabs on exposed south-facing slopes. Light snow and westerly winds could form pockets of fresh wind slab on east-facing slopes, or hide the older hard wind slabs.

Use ridges or ribs to avoid pockets of wind loaded snow.>Watch for areas of hard wind slab in steep south-facing alpine features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Several persistent weak layers exist in the upper to middle snowpack. It might take a large load (like a cornice fall), major weather input (heavy rain or snow), or a rider hitting the sweet spot to trigger this problem.

Avoid convexities or areas with a thin or variable snowpack where triggering is more likely.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 2nd, 2015 2:00PM