Avalanche Forecast

Issued: Dec 26th, 2017 4:59PM

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 on lee slopes.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

WEDNESDAY: Mostly cloudy, strong west winds, treeline temperatures around -17 C.THURSDAY: Cloudy with flurries starting in the afternoon, strong west winds, treeline temperatures around -15 C.FRIDAY: 10-20 cm of low-density snow, strong west winds, treeline temperatures around -15 C.

Avalanche Summary

On Monday, one large (size 2) naturally-triggered avalanche was reported on a north-facing alpine feature that likely failed on the mid-December surface hoar layer. Otherwise, avalanche activity has generally quieted down as the cold weather sets in. There have been some isolated reports of whumpfs at small avalanches failing on the mid-December surface hoar layer, but in most areas the snow above this layer has not settled into a slab yet.The current forecasters' blog has additional advice on the developing persistent slab problem (click here).

Snowpack Summary

Cold temperatures are preserving roughly 50 cm of low density snow from last week's storms. The snow is being deposited into harder wind slabs in exposed terrain, but remains low density in sheltered areas. The main question in the snowpack surrounds the mid-December layer sitting beneath the new snow. The layer includes crusts on south and west facing slopes and large feathery surface hoar crystals in sheltered areas 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 formed stiff slabs above the layer and on slopes with preserved surface hoar. The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November.

Problems

Wind Slabs

An icon showing Wind Slabs
Expect wind slabs at higher elevations where wind has formed pockets of hard snow on the downwind sides of ridges and gullies.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use ridges or ribs to avoid pockets of wind loaded snow.

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 40-60 cm below the surface. Triggering an avalanche on this layer is possible in areas where the snow has settled into a cohesive slab.
Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Watch for whumpfing, hollow sounds, and shooting cracks.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 27th, 2017 2:00PM

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