Avalanche Forecast

Issued: Apr 19th, 2012 10:23AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs, Loose Wet and Wet Slabs.

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

An approaching frontal system is expected to reach the Interior Thursday night, bringing moderate amounts of snow at upper elevations. Overnight Thursday: Snow amounts 10-20 cm. Ridgetop winds moderate from the SW. Freezing levels 1300 m. Friday: Snow amounts 2-5 cm. Ridgetop winds moderate from the SW. Freezing levels 1700 m. Saturday/Sunday: An upper ridge of high pressure will bring mainly dry, sunny conditions on Saturday. Ridgetop winds light from the West. Freezing levels valley bottom rising to 1800 m by the afternoon. High cloud, and light precipitation expected Sunday. Freezing levels rising to 2500 m, and look to persist through the evening.

Avalanche Summary

No recent observations have been submitted. On Tuesday, avalanche observations include a couple of skier triggered (controlled) size 1.5 loose wet avalanches from East aspects. Wind slabs, loose dry and wet slabs are likely avalanche problems for the weekend to come.

Snowpack Summary

Forecast new snow and wind may build wind slabs on lee slopes and behind terrain features. Recent, spring-like conditions exist, with a melt-freeze crusts on most aspects, with the exemption of higher North facing slopes. Since last weekend, mostly light to locally, low density, moderate amounts of new snow have fallen forming soft slabs on the resulting crust while rain has continued to penetrate and weaken the snowpack at lower elevations. Up to 80cm below the surface, you will find another crust in the alpine and at treeline that may have been reactive (most likely on Southerly aspects) with warming throughout last week. The mid-February buried surface hoar layer is down about 200 cm, although avalanches releasing on this layer represent an extremely low probability-high consequence scenario. Cornices in the region are very large. With spring temperatures, these are more likely to become weak and fail. They could provide a large enough trigger to release deep layers on slopes below. For more information on Spring Conditions and ways to mitigate risk, please visit the new Forecasters Blog Post.

Problems

Wind Slabs

An icon showing Wind Slabs
New wind slabs may develop with forecast wind and snow. Watch for these behind ridgecrests and terrain breaks. Sluffing, and loose snow avalanches are likely from steeper slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

An icon showing Loose Wet
Snow stability can deteriorate very quickly with spring temperatures. Watch for loose wet avalanches on steep terrain, especially if the sun is shining.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wet Slabs

An icon showing Wet Slabs
Buried crusts will provide an ideal sliding layer for wet slabs, especially on rain soaked and sun-exposed slopes. Warmer temperatures at lower elevations are also a contributing factor. Spring temperatures will also promote glide crack activity.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Apr 20th, 2012 9:00AM