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Avalanche Forecast

Archived

Feb 17th, 2017–Feb 18th, 2017

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

Regions

Kananaskis.

Warm temps are helping to strengthen the snowpack at the lower elevations but treeline and alpine we still have a concern from natural and human triggered avalanches.

Confidence

High - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Temperatures will remain seasonal on Saturday with daytime highs around -5 at 2500m (treeline).  5-10cm of new snow is forecast to fall and winds will be light to moderate out of the SW.  Freezing levels will be around 1800m.

Avalanche Summary

No new natural avalanche activity was observed over the past 24hrs.

Snowpack Summary

5-15cm of recent snow is now overlying a widespread temperature crust at lower elevations (up to 2000m) and likely up to 2400m on pure solar aspects. As you climb into the alpine this new snow has been blown into thin (20-30cm) thick storm slabs.  Field tests on Friday were showing these storm slabs to be unreactive to ski cutting but we werent willing to expose ourselves to larger slopes due to the weak faceteted basal layers down 100-120cm.  Warm temps are helping to settle out the snowpack and strengthen it but this process takes time.  We still have very little confidence in the stability of any large terrain feature and are continuing to limit our exposure to overhead terrain.  Good skiing was being found in sheltered areas at TL and below.  Field teams were not in alpine areas.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.