Avalanche Forecast

Issued: Jan 9th, 2015 7:34AM

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.

Avalanche Canada Peter, Avalanche Canada

Keep the persistent slab problem in mind when you choose terrain this week. The likelihood of triggering it may be low, but the consequences could be high.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Synopsis: The ridge of high pressure gives way to weak upper trough on Saturday bringing more cloud and unsettled conditions through Sunday. We could see flurries on the weekend but no significant accumulation. Ridge winds are generally light or moderate from the W-NW. The ridge should rebuild on Monday bringing drier conditions and more sunshine. The freezing level remains at valley bottom throughout the period.

Avalanche Summary

One observer north of Sparwood reported one natural size 1.5 slab avalanche and one remotely triggered size 2 avalanche on Wednesday, both sliding on the buried crust layer down 30-50 cm. On Tuesday, there was one report of a size 2.5 natural slab avalanche from Allison Peak in the Crowsnest Pass.

Snowpack Summary

Below treeline and on south-facing slopes there may be a melt-freeze crust overlying up to 20 cm of recent snow. At higher elevations the new snow has been blown into wind slabs in exposed lee terrain. The recent snow sits on hard wind slabs in exposed terrain, and low density faceted snow in sheltered areas. Up to 75 cm below the surface you will likely find a hard, thick crust which formed mid-December. This crust has overlying facets and surface hoar (up to 10 mm in sheltered locations at treeline and below). This layer seems variably reactive throughout the region. In areas where the overlying slab is thick and cohesive, large avalanches are possible at this interface. A crust/facet combo which formed in November seems to have gone dormant for the time being.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent West or Northwest winds have probably created fresh wind slabs in exposed lee terrain. 
Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
A buried persistent weakness, down 30-50 cm, should remain on your radar as it has the potential to produce large avalanches.
Avoid convexities or areas with a thin or variable snowpack where triggering could be more likely.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Jan 10th, 2015 2:00PM

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