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Avalanche Forecast

Archived

Jan 10th, 2014–Jan 11th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Rockies.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Tonight and Saturday: A strong low pressure system will track over the province tonight leaving moderate to heavy precipitation on the region tonight and tomorrow. Around 20-30 mm in water equivalent is forecasted. This will be accompanied by strong winds from the SW during the night and during the day tomorrow. Freezing levels are expected to rise to 1500 m tonight and lower to 1100 m tomorrow. Sunday: Another system is tracking through the province but is not expected to leaving light amounts of precipitation over the region. Moderate W winds should increase in speed during the day. Freezing levels are forecasted to rise back up but there is some disagreement between models.Monday: Light to moderate precipitation as a cold front moves across the interior with similar freezing levels.

Avalanche Summary

Multiple natural and skier triggered loose dry avalanches and slab avalanches up to size 1 were reported yesterday.

Snowpack Summary

The significant amounts of snow forecasted tonight and tomorrow, the strong SW winds redistributing this snow and warmer temperatures is increasing the avalanche danger for tomorrow. Windslabs lee of SW winds below ridgetop in the alpine and at treeline will be very touchy and the storm snow in sheltered areas will also need time to settle. Cornices will continue building and could fall with this additional load. Yesterday's 10-20 cm created some windslabs in the alpine lee of W-SW winds which could be hidden by the new snow that will fall tonight and tomorrow. When tested and observed, the surface hoar layer down 70 cm is showing signs of healing (grains are rounding and snowpack tests are not as planar as they have been previously).The facet/crust layer down 80-100 cm at treeline has been mostly reactive on E aspects and the depth hoar layer in the alpine is still concern especially where the snowpack is thinner. 

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.