Avalanche Forecast

Issued: Dec 27th, 2017 4:48PM

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

Avalanche Canada shorton, Avalanche Canada

Winds are expected to increase, so watch for slab development in exposed terrain.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

THURSDAY: Cloudy with flurries starting in the afternoon, strong west winds, treeline temperatures around -17 C.FRIDAY: 5-20 cm of low density snow, strong west winds, treeline temperatures around -20 C.SATURDAY: Another pulse of snow with 5-30 cm possible, strong west winds, treeline temperatures around -23 C.

Avalanche Summary

Limited reports suggest triggering slab avalanches remains possible. Two skier triggered avalanches have been reported east of the divide the past few days. One was a small wind slab triggered in a steep gully and the other was a larger persistent slab (size 2) triggered low on a slope that propagated up and across the slope on a 50 cm deep crust. The later highlights the potential for persistent slab avalanches to have wide propagations.

Snowpack Summary

Cold temperatures are preserving fresh snow from the past week, with up to 60 cm in southern and eastern parts of the region and 30 cm in the Elk Valley. The snow has been deposited into harder wind slabs in exposed terrain, but remains low density in sheltered areas.The main question in the snowpack surrounds the layer sitting beneath the recent snow. The layer includes crusts on solar aspects and feathery surface hoar in sheltered terrain at and below treeline. The distribution of the layer, as well as the properties of the snow above it, is variable. The most suspect areas are where the wind has blown extra snow above this layer and on slopes with preserved surface hoar.The lower snowpack is composed of mostly soft sugary snow and a few early season crusts that have not produced significant test results recently.

Problems

Wind Slabs

An icon showing Wind Slabs
Expect fresh wind slabs to develop throughout the day on the downwind sides of ridges and gullies.
Use ridges or ribs to avoid pockets of wind loaded snow.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer composed of surface hoar and/or crusts is buried 30-60 cm below the surface. Triggering an avalanche on this layer is possible in areas where the snow has settled into a cohesive slab.
Watch for signs of instability such as whumpfing, or cracking. Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 28th, 2017 2:00PM