Avalanche Forecast

Issued: Dec 27th, 2017 4:49PM

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

Danger will increase this week as snow and strong winds are expected to start on Thursday afternoon.

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 -15 C.FRIDAY: 10-20 cm of low density snow, strong west winds, treeline temperatures around -17 C.SATURDAY: Another pulse of snow with 10-30 cm possible, strong west winds, treeline temperatures around -20 C.

Avalanche Summary

No recent avalanches have been reported. On Monday, one large naturally-triggered avalanche (size 2) was reported on a north-facing alpine feature that likely failed on the mid-December surface hoar layer. 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.

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 buried 50 cm below the surface. The layer includes crusts on south and west facing slopes and feathery surface hoar 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 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.Minimize exposure during periods of heavy loading from new snow and wind.

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

Elevations: Alpine, Treeline.

Likelihood

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.Choose well supported terrain without convexities.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

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

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