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Avalanche Forecast

Feb 27th, 2017–Feb 28th, 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
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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: Cariboos.

Danger will increase throughout the week with new snow and strong winds in the forecast. Triggering a deep persistent slab is the primary concern and warrants a cautious approach to terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

TUESDAY: Cloudy with flurries starting in the afternoon, moderate southwest winds with strong gusts, alpine temperatures around -15 C.WEDNESDAY: Continued flurries with 5-10 cm of new snow, moderate southwest winds with strong gusts, alpine temperatures around -10 C.THURSDAY: Another 10 cm of new snow, strong southwest winds,  alpine temperatures around -8 C.

Avalanche Summary

On the weekend several natural wind slabs in the size 1-2 range were reported in steep alpine terrain. Many parts of the region have a similar snowpack structure to Clemina Creek, where two size 2 snowmobile triggered persistent slab avalanches were reported on Saturday (see MIN report here). Triggering a large deep persistent slab avalanche is a low probability - high consequence scenario that warrants an extra cautious approach to terrain. See here for a list of recent near misses in the Cariboos and North Rockies.

Snowpack Summary

New wind slabs have formed on a variety of aspects in alpine terrain thanks to shifting wind directions. Light flurries over the past week have delivered a total of 15-30 cm of low density snow, while sun crusts have formed on steep south slopes. The recent snow has buried the mid-February interface, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. Some lingering surface hoar layers from January are down about a metre and the weak mid-December facets are down about 1.5 metres. These deep persistent weaknesses still have the potential to react to human triggers.

Avalanche Problems

Deep Persistent Slabs

A lingering weak layer of facets near the bottom of the snowpack may be triggered in shallow snowpack areas and produce large avalanches.
Avoid lingering in runout zones.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Carefully evaluate and use caution around thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3

Wind Slabs

Watch for fresh wind slabs in the immediate lee of ridges and crossloaded alpine terrain.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.Avoid recently wind loaded features.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 2