Avalanche Forecast

Issued: Apr 7th, 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, Storm Slabs and Persistent Slabs.

Alberta Parks jeremy.mackenzie, Alberta Parks

Though we are not completely into spring snowpack conditions, solar radiation and daytime heating will be the big factors on Sunday. It is time to start early and finish early. Don't underestimate the de-stabilizing affects of the April sun.

Summary

Confidence

Good - Timing or intensity of solar radiation is uncertain

Weather Forecast

A sunny and relatively calm morning is expected on Sunday with intense solar radiation and rising temperatures. Convective flurries are likely in the afternoon.

Avalanche Summary

A few loose dry slides were observed today on steep N and E aspects up to size 2.0. Also, some small loose wet avalanches occurred on sunny slopes in the afternoon. A very large slide (size 3.5) occurred sometime on Friday in the Tyrwhitt region. This avalanche failed on both the February surface hoar and the basal facets and destroyed approximately 2 Ha of mature forest. It is quite possible that we will see large avalanches as we transition to spring due to a deeper than average snowpack and two concerning deeply buried weak layers.

Snowpack Summary

No new snow overnight, but lots of low density snow is available for transport. Wind loading is occurring at alpine and treeline elevations on lee slopes. On E, S and W aspects crusts are forming each evening and melting each day. The extent of melting is related to the amount of radiation and the air temperatures. Dry snow remains on N aspects above 1900m in most locations. The snowpack is settling. The deeply buried February surface hoar and basal facets are sporadically active in large natural avalanche events, including some triggered by cornice failures.

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

Storm Slabs

An icon showing Storm Slabs
Recent snow, warm temps and winds are creating storm slabs in open terrain. These slabs will become more touchy as they gain density, but so far they are only sensitive just below ridgetop and in cross-loaded features. This could change on Sunday.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The February surface hoar is buried 120-150cm 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

Valid until: Apr 8th, 2012 9:00AM