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Avalanche Forecast

Dec 26th, 2017–Dec 27th, 2017
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

Winds are expected to increase, so watch for slopes getting loaded with blowing snow.

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

WEDNESDAY: Mix of sun and cloud, strong west winds, treeline temperatures around -20 C.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 -17 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 new snow. The layer includes crusts on solar aspects and large feathery surface hoar crystals 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.Two crusts that were buried near the end of November can be found lower in the snowpack. A third crust from the end of October exists near the base of the snowpack. Recent testing on these crusts has not produced significant results.

Avalanche Problems

Wind Slabs

Expect slabs at higher elevations where wind has formed hard deposits of 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.Give the recent storm snow plenty of time to bond to underlying layers.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

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.
Choose well supported terrain without convexities.Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2