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Avalanche Forecast

Jan 12th, 2014–Jan 13th, 2014
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Overnight : Flurries with trace amounts of precipitation, winds from the west at ridgetop 30 to 60 km/h, freezing level rising to 700m.Monday: Flurries with trace amounts of precipitation, strong winds from the W-NW at ridgetop gusting to 100 km/h, freezing level rising to 1200 M.Tuesday: No Precipitation in the forecast, moderate to strong winds from the west, freezing levels may rise to 1500m in parts of the forecast area.Wednesday: No Precipitation in the forecast, moderate winds from the west, freezing level should come down to 1200m in parts of the forecast area.

Avalanche Summary

There have been a number close calls with large avalanches in the north of this region in the last three weeks. Check out the incident database for more details. Recent reports of numerous skier controlled size 1 to 2's days indicate the severity of the new snow and wind loaded snow instability. There is a very real possibility that a small avalanche could "step down" to the weaker facetted layer at the base of the snowpack and produce a large destructive avalanche.

Snowpack Summary

Amounts of new snow are highly variable over the length of the forecast area, with the western parts of the range getting as much as 40 cm in the past 24 hrs, and the eastern and southern parts receiving 15 to 20. The new snow sits on a variety of snow surfaces including older wind slabs and a soft layer of facetted snow and/or surface hoar. These sit on top of older wind slabs and a couple of persistent weak layers that exist in the upper meter of the relatively thin snowpack. The mid December surface hoar is buried around 30-90 cm. The early December facet/crust combo is buried down 50-150 cm. Both interfaces give variable results with snowpack tests, but professional operators are treating them with caution.A big concern, especially in the northern part of the region is a layer of weak sugary depth hoar crystals at the base of the snowpack that lie above a crust from early October. Several large avalanches in the last two weeks have been attributed to failures at this layer. Wide propagations on relatively gentle terrain have been noted, as well as a tendency for seemingly disconnected slopes to propagate over a wide area and produce large avalanches.

Avalanche Problems

Storm Slabs

Careful consideration is needed to travel and/or ski safely in the back country at this time.  Be aware wind loaded slopes, thin snowpack areas and overhead hazards,
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid all avalanche terrain.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Stick to simple terrain and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 5

Persistent Slabs

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 5

Deep Persistent Slabs

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 6