Avalanche Forecast

Issued: Apr 8th, 2012 4:00PM

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

Alberta Parks jeremy.mackenzie, Alberta Parks

Mon and Tues could see freezing levels as high as 3000m and intense solar radiation which will keep the danger level elevated. Start your trip early and finish early. Still winter conditions on N aspects, but all other slopes have crusts in the AM.

Summary

Confidence

Good - Freezing levels are uncertain

Weather Forecast

Sunny and warm again on monday with freezing levels climbing as high as 3100m. Winds will be light and no precipitation is expected. A storm is a approaching, but timing is unclear if it will arrive Wednesday or Thursday.

Avalanche Summary

Numerous solar triggered loose wet slides up to size 2.0 were observed today. A cornice triggered size 2.5 slab avalanche occurred sometime in the past 36 hours on a steep NW aspect in the alpine near Chester Lake. Cornice failures have triggered very large slides on underlying slopes over the past week, and remain active with the recent intense solar radiation.

Snowpack Summary

True North aspects remain dry all the way to valley floor, but all other slopes (all aspects, all elevations) have one or more crusts. These crusts were melting and solar triggering of avalanches began on SE aspects by 11:00am and then continued around to the S, then W aspects in the afternoon. Pockets of windslab exist at alpine and treeline elevations on lee aspects and stability tests indicate that these slabs are skier triggerable in steep and unsupported terrain. Cornices are quite large. the February surface hoar and the basal facets have become a concern again as the snowpack transitions to spring-time conditions. Very large avalanches are expected if these layers are triggered by solar radiation and/or cornice failures. Human triggering is also possible from shallow snowpack areas.

Problems

Loose Wet

An icon showing Loose Wet
Loose wet slides related to daytime warming are being observed on solar aspects. Pay close attention to terrain that is overhead as you travel. The intense spring-time sunshine does not take much time to change the snow stability.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The February surface hoar is buried up to 140cm at treeline. This interface is still hard to trigger, but it has come back alive in recent cornice triggered avalanches. The spring transition could see more avalanches stepping down to this layer.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Wind Slabs

An icon showing Wind Slabs
Wind slabs are present in lee and cross loaded features at higher elevations. Stability tests today indicate that these slabs are sensitive to human triggers in steep, convex and/or unsupported terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

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

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